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Viruslarni aniqlab bo'lmaydigan qiladigan hayotning ta'rifi bormi?

Viruslarni aniqlab bo'lmaydigan qiladigan hayotning ta'rifi bormi?


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Hayotning turli xil ta'riflari mavjud (RNK, evolyutsiya natijasida paydo bo'lgan), lekin men ko'rmaganim yo'q, bu viruslar tirik mavjudot ekanligini aniqlay olmadi (garchi "ha" va "yo'q" ta'riflari ko'p bo'lsa ham). Bunday ta'riflar bormi (men to'g'ri lug'at ta'rifi uchun kurashibgina qolmay, bu haqiqatan ham fundamental munozara bo'lgan holatlarni qidiryapman)?

Rahmat.


Sizning oxirgi jumlangiz kalit: hayotni aniqlash - bu biz kelishib oladigan lug'at ta'rifini topishdir. Biologiya - bu ba'zida alohida ta'riflarni rad qiladigan narsa: "Tirik bo'lish nima?" "Tur nima?" balki "genning yovvoyi turi allel nima?" Men viruslarga ularning tirik yoki yo'qligini aniqlash uchun qiyinchilik sifatida qaramaslikni tavsiya qilaman, chunki biz hayotning muhim xususiyatlari deb hisoblagan narsalarni muhokama qilish uchun ajoyib imkoniyatdir. Hayotni navbat bilan quyidagicha ta'riflash mumkin: "O'z-o'zini ko'paytiruvchi hujayralardan tashkil topgan" ("Hayotning hujayra nazariyasi" ning tarjimasi yoki quyidagi xususiyatlarning kamida ko'pini o'zida mujassam etgan narsalar sifatida: 1. O'z-o'zini ko'paytirish 2. Metabolizma 3. O'sish. 4. Moslashuv belgilarini ko'rsatish 5. Uyushtirilganlik 6. Atrof-muhitga javob berish 7. Hujayralardan iborat

Men hayotni aniqlayotganda, biz sayyoradan tashqari shakllarga e'tibor qaratishimiz kerak deb o'ylashni yaxshi ko'raman. ya'ni biz uni "hayot" deb atash uchun o'zga sayyorada nimani ko'rishni xohlar edik? Ba'zilar viruslarni er yuzida tirik deb atashdan qiynalayotgan bo'lsa-da, o'sha odamlar biz boshqa sayyorada yerdan tashqari hayotni topdik, deb aytishga tayyor bo'lishi mumkin, agar u shunga o'xshash bo'lsa (to'g'ri, bunday hayotni xostsiz tasavvur qilish qiyin ...)

Bundan tashqari, siz ushbu savolning ushbu to'plamga mos keladimi yoki yo'qligini so'rashingiz mumkin, chunki uni adabiyotlar bilan qo'llab-quvvatlab bo'lmaydi (hech bo'lmaganda hech qanday xulosani qo'llab-quvvatlamaydi). Xo'sh, buni "Biologiya" yoki "Falsafa" deb yozish kerakmi?


Virusning jonli va jonsiz xususiyatlarini aytib bering

Virus submikroskopik element bo'lib, tirik hujayralarni ifloslantiradi. Ular hujayrali bo'lmagan organizmlar bo'lib, ular tirik hujayralarni bosib o'tishi mumkin bo'lgan genetik material va oqsildan iborat. Ular ancha kichikroq, o'lchamlari taxminan 20-300 nanometr (nm) ni tashkil qiladi, lekin ba'zilari kattaroq bo'lishi mumkin. Ular fotosintez qilmaydi, chunki ularda xloroplastlar yoki xlorofill yo'q.

Viruslar tirik deb tasniflanmaydi, chunki ularning ko'payish mexanizmi yo'q. Viruslar tirik organizmlar bo'ladimi yoki oddiy molekulalar konglomeratsiyalari bo'ladimi, ko'p yillar davomida munozaralarga asos bo'lgan.

Virusning yashash xususiyatlari –

  • Har bir virus DNK, RNK va oqsildan iborat.
  • Ular tirik hujayralar ichida ko'payishi mumkin,
  • Patogen bakteriyalar singari, u ham tirik hujayrasiz yashay olmaydi.
  • Bunda genetik rekombinatsiya sodir bo'lishi aniqlandi.
  • Mutatsiyaning paydo bo'lishi aniqlandi,
  • Ularning genetik ob'ektlari bor,
  • Ular xost hujayralari ichida o'sishi va ko'payishi mumkin
  • Maxsus irqlar yoki shtammlar mavjud
  • Ular bir xostdan ikkinchisiga uzatilishi mumkin.
  • Ular uy egasida ko'paytirishga qodir.
  • Ular mutatsiyalarni ko'rsatadi
  • Ular asabiylikni namoyon qiladilar, chunki ular issiqlik, radiatsiya va kimyoviy moddalarga ta'sir ko'rsatadi.
  • Ular ko'payishga qodir va shuning uchun ularning sonini ko'paytirishi mumkin.
  • Ular antibiotiklarga chidamli.

Viruslar quyidagi xususiyatlarga ko'ra tirik emasligi aniqlanadi:

Tirik bo'lmagan xususiyatlar:

  • Uning alohida hujayrasi yo'q,
  • Individualistik virus boshqa tirik hujayrada yashamasdan organik faoliyatni amalga oshira olmaydi,
  • Ularda sitoplazma, yadro va boshqa hujayra yo'q va metabolik fermentlar yo'q,
  • Kristal granulalar tayyorlanishi mumkin,
  • Ular RNK va DNKni birga o'z ichiga olmaydi.
  • Ularda tirik hujayralar tashqarisida metabolik faollik yo'q.
  • Ularda nuklein kislotasi va oqsil sintezi uchun zarur bo'lgan ribosomalar va hujayrali fermentlar etishmaydi.
  • Ularda hujayra membranasi va hujayra devori yo'q.
  • Don metabolizmasidan o'tmaydi va harakatchanlik yo'q
  • Hech qanday energiya konvertatsiyasi va ogohlantirishlarga reaktsiya yo'q
  • Tirik hujayralar tashqarisida ko'payish yo'q
  • Ular kristallanishi va cho'ktirilishi mumkin
  • Hujayralarning tashqi qismi inert kimyoviy moddalar kabi harakat qiladi
  • Ular o'sish, rivojlanish, ovqatlanish, ko'payish va hokazolarni ko'rsatmaydi.
  • ’t hajmi, shakli yoki shunga o'xshash o'sishi mumkin emas. Hech qanday ozuqaviy moddalarga ega bo'lmang.
  • Nafas olmang yoki nafas olmang, shuningdek, chiqarmang.
  • Har qanday energiya ishlab chiqaruvchi tizimning yo'qligi va ularning ko'payishi va metabolizmi xo'jayiniga to'liq bog'liq.
  • Ular hujayra bo'linishini, o'sishini, rivojlanishini, ovqatlanishini va hokazolarni ko'rsatmaydi.
  • Ularda uyali aloqa etishmaydi. Hujayrani yuqtirgandan so'ng, ular o'zlarini ko'paytirish uchun mezbon hujayraning mexanizmlarini egallab olishadi.

Viruslar oqsillar, nuklein kislotalar, lipidlar va uglevodlarni o'z ichiga olgan molekulalarning murakkab birikmalaridir, lekin ular mustaqil ravishda tirik hujayraga kirmaguncha hech narsa qila olmaydi. Hujayralarsiz viruslar ko'payishi mumkin emas edi. Shuning uchun viruslar tirik mavjudotlar emas.

Virus zarrachani hosil qiluvchi ultramikroskopik hujayrasiz kasallik sifatida ham tanilgan. Bu o'simlik va hayvonlar uchun ko'plab kasalliklarni keltirib chiqaradi. Ularda hujayrali nafas yo'q, chunki ular hujayra emas, shuning uchun antibiotiklar viruslarga ta'sir qilmaydi.


5 -hayot shohligida viruslarning tasnifi

Barcha tirik mavjudotlarni oltita qirollikdan biriga bo'lish mumkin va ular beshta asosiy xususiyatlarga ega. Barcha tirik organizmlar umumiy xususiyatlarga ega va ular beshta asosiy xususiyatga ega. Ular: hujayrali uyushish, metabolizm, gomeostaz, o'sish va ko'payish va irsiyat. (Jonson, 2010, 15 -bet) Bu tirik mavjudotlar oltita guruhga bo'linadi, ular "Qirollik" deb nomlanadi. Oltita shohlik - bu bakteriyalar, arxeya, protista, zamburug'lar, planta va hayvonot dunyosi.

Viruslar yuqoridagi 5 hayot shohligiga tegishli emas. Ular hujayralarga qaraganda ancha kichik va murakkabroqdir. Ular tashqi oqsil qobig'i bilan o'ralgan DNK yoki RNKdan tashkil topgan makromolekulyar birliklardir. Ularda membrana bilan bog'langan organellalar, ribosomalar (oqsil sintezining organelli joyi), sitoplazma (hujayraning tirik tarkibi) va o'z-o'zidan energiya ishlab chiqarish manbai yo'q. Ular avtopoezni namoyish qilmaydi-ya'ni. ularda tirik tizimlarning o'z-o'zini ushlab turadigan metabolik reaktsiyalari yo'q. Viruslarda hujayrali nafas olish, ATP-ishlab chiqarish, gaz almashinuvi va boshqalar yo'q. Ammo ular ko'payadi, lekin xujayra hisobiga. Majburiy parazitlar singari, ular ham faqat tirik hujayralarda ko'payishga qodir. Qaysidir ma'noda, viruslar xost hujayrasini o'g'irlaydi va uni DNK replikatsiyasi va oqsil sintezi orqali ko'proq viruslar ishlab chiqarishga majbur qiladi. Viruslar xost hujayralaridan tashqarida kichik makromolekulyar zarrachalar sifatida omon qolishi mumkin. Viruslar hayvonlar va o'simliklarga hujum qilishi mumkin. Yuqumli odam viruslari havo (havodagi viruslar) yoki tana suyuqliklari (OIV virusi) orqali tarqalishi mumkin. Jinsiy konjugatsiya orqali odamdan odamga o'tadigan epidemik viruslar (masalan, OIV) kompyuter viruslariga juda o'xshaydi. Afsuski, odamlarda sizni potentsial infektsiya haqida ogohlantiradigan yoki tanangizni tezda skanerdan o'tkazadigan va sizning tizimingizga kirganidan so'ng uni yo'q qiladigan antivirus dasturi yo'q. Odamlar o'zlarining ajoyib antikorlari va hujayra vositachiligidagi immunitetiga tayanishi kerak, bu dunyodagi eng murakkab va ajoyib yutuqlardan biri.


Iqtibos: Jonson, G. (2010). Tirik dunyoning asosiy qismi. Nyu-York shahri: McGraw-Hill Companies, Inc.
Zimmer, C. (2007 yil iyul). O'RAMIZDA O'G'ILGANLAR. Discover jurnali, jild. 28, 7-son.


Hayotni nima belgilaydi?

Tirikni tirikdan ajratib turadigan aniq ta'rif yo'q. Ta'riflardan biri bu shaxsning o'zini o'zi anglash nuqtasi bo'lishi mumkin. Shu ma'noda, og'ir bosh jarohati olgan kishi miya o'liklari sifatida tasniflanishi mumkin. Bunday holda, tana va miya hali ham asosiy darajada ishlaydi va kattaroq organizmni tashkil etuvchi barcha hujayralarda, albatta, metabolik faollik mavjud, lekin o'z-o'zini anglash yo'q, deb taxmin qilinadi, shuning uchun odam shunday deb tasniflanadi. miya o'lik. Spektrning boshqa chekkasida, hayotni belgilashning boshqa mezoni - genetik rejani kelajak avlodlarga ko'chirish qobiliyati bo'ladi va shu bilan sizning qiyofangizni qayta tiklaydi. Ikkinchi, soddalashtirilgan ta'rifda viruslar, albatta, tirikdir. Ular, shubhasiz, bu sayyoradagi genetik ma'lumotlarini tarqatishda eng samarali mavjudotlardir.

Viruslarni tirik mavjudot deb hisoblash mumkinmi, degan savolga aniq qaror bo'lmasa -da, ularning genetik ma'lumotni kelajak avlodlarga etkazish qobiliyati evolyutsion ma'noda ularni asosiy o'yinchilarga aylantiradi.


Tegishli manbalar:

  • Viruslar tirikmi? Scientific American jurnalidagi ushbu maqolada tirik va jonsiz viruslar biologiyada qanday tasniflanishi va ularning evolyutsiyadagi roli muhokama qilinadi. (qo'shimcha ma'lumot)
  • Mimivirusning 1,2 megabazali genom ketma-ketligi. Science jurnalidagi ushbu asosiy tadqiqot maqolasida ma'lum bo'lgan eng katta virus genomi va uning kashfiyoti viruslar va parazit hujayrali organizmlar o'rtasidagi farqni qanday yo'q qilishini muhokama qiladi. (ko'proq ma'lumot)

'life' uchun 100 dan ortiq ta'riflar mavjud va ularning barchasi noto'g'ri

Ko'pchiligimiz, ehtimol, tirik mavjudotlarni "tiriklar" dan ajratish uchun ko'p o'ylashimiz shart emas. Inson tirik, tosh emas. Oson!

Olimlar va faylasuflar buni aniq ko'rmaydilar. Ular ming yillar davomida nimalarni tiriklayapti deb o'ylashdi. Aristoteldan tortib Karl Sagangacha bo'lgan buyuk aqlli odamlar bu haqda bir oz o'ylab ko'rishgan va ular hali hammaning xohishiga mos keladigan ta'rifni o'ylab topishmagan. To'liq ma'noda, bizda hali hayot uchun "ma'no" yo'q.

Agar biror narsa bo'lsa, so'nggi 100 yil ichida hayotni aniqlash muammosi yanada qiyinlashdi. 19 -asrga qadar bitta g'oya keng tarqalgan edi: hayot nomoddiy ruh yoki "hayotiy uchqun" mavjudligi tufayli alohida. Bu fikr hozir ilmiy doiralarda yoqmay qoldi. O'shandan beri u ko'proq ilmiy yondashuvlar bilan almashtirildi. Misol uchun, NASA hayotni "darvin evolyutsiyasiga qodir bo'lgan o'z-o'zini ta'minlaydigan kimyoviy tizim" deb ta'riflagan.

Ammo NASA - bu butun hayotni oddiy ta'rif bilan cheklashga urinishlardan biri. Aslida, hayotning 100 dan ortiq ta'riflari taklif qilingan, ularning aksariyati replikatsiya va metabolizm kabi bir nechta asosiy atributlarga qaratilgan.

Vaziyatni yomonlashtiradigan bo'lsak, har xil turdagi olimlar haqiqatan ham tirik narsani aniqlash uchun zarur bo'lgan narsalar haqida turlicha tasavvurga ega. Kimyogar hayot ma'lum molekulalarga bog'liq deb aytishi mumkin bo'lsa, fizik termodinamikani muhokama qilmoqchi bo'lishi mumkin.

Nima uchun hayotni aniqlash qiyinligini yaxshiroq tushunish uchun, keling, tirik mavjudotlarni hamma narsadan ajratib turadigan chegarada ishlayotgan ba'zi olimlar bilan tanishaylik.

Virusologlar: biz bilganimizdek, hayotning chekkasidagi kulrang maydonni o'rganish

Siz maktabda GREN xonim bilan uchrashdingizmi? Bu qulay mnemonika - bu bolalar hayotni aniqlaydigan ettita jarayonni eslab qolishning bir usuli: harakat, nafas olish, sezuvchanlik, o'sish, ko'payish, ajralish va ovqatlanish.

Hayotning 100 dan ortiq ta'riflari taklif qilingan

Bu hayotni belgilash uchun foydali boshlang'ich nuqta bo'lsa-da, bu aniq emas. Biz odatdagidek yashaydigan deb tasnif qilmagan ko'p narsalar bor, bu qutilarga belgi qo'yish mumkin. Ba'zi kristallar, prionlar deb ataladigan yuqumli oqsillar va hatto ba'zi kompyuter dasturlari MRS GRENga ko'ra "tirik".

Klassik chegara holati viruslardir. "Ular hujayralar emas, ular metabolizmga ega emaslar va ular hujayra bilan to'qnash kelmaguncha inertdirlar, shuning uchun ko'p odamlar (shu jumladan ko'plab olimlar) viruslar tirik emas degan xulosaga kelishadi", deydi Paster mikrobiologi Patrik Forter. Parijdagi institut, Frantsiya.

O'z navbatida, Forterre viruslar tirik deb o'ylaydi, lekin u qaror haqiqatan ham kesish nuqtasini qaerga qo'yishga qaror qilganingizga bog'liqligini tan oladi.

Viruslarda hayot klubiga a'zo bo'lish uchun zarur bo'lgan deyarli hamma narsa bo'lmasa-da, ular DNK yoki RNKda kodlangan ma'lumotlarga ega. Sayyoradagi har bir tirik mavjudot bilan bo'lishilgan bu hayotiy reja shuni anglatadiki, viruslar faqat tirik hujayralar mexanizmini o'g'irlash orqali rivojlanib, ko'payishi mumkin.

Viruslar va biz bilgan barcha hayot kabi va DNK yoki RNKni olib yurishi ba'zilarni viruslar bizning hayot daraxtimizga tegishli bo'lishi kerak degan fikrga olib keldi. Boshqalar, hatto, viruslar hayot birinchi navbatda qanday boshlanganini tushunishga yordam beradi, deb da'vo qilishdi. Agar shunday bo'lsa, hayot oq-qora mavjudotga o'xshamaydi va ko'proq jonli va o'lik bo'lmagan chegaralarni chalkashtirib yuboradigan tumanli miqdorga o'xshay boshlaydi.

Ba'zi olimlar bu fikrni qabul qilishdi. Ular viruslarni "kimyo va hayot chegarasida" mavjud deb ta'riflaydilar. Va bu qiziq savol tug'diradi: kimyo qachon uning qismlari yig'indisidan ko'proq bo'ladi?

Kimyogarlar: hayot retseptini o'rganish

San-Diegodagi (Kaliforniya) Skripps okeanografiya institutidan Jeffri Bada: "Biz bilganimizdek, hayot uglerod asosidagi polimerlarga asoslangan", deydi. Ushbu polimerlardan va ndash, ya'ni nuklein kislotalar (DNKning qurilish bloklari), oqsillar va polisaxaridlar va hayotning deyarli barcha xilma-xilligi quriladi.

Bada Stenli Millerning shogirdi edi, 1950-yillardagi Miller-Urey eksperimentining yarmi va hayot tirik bo'lmagan kimyoviy moddalardan kelib chiqqan degan fikrni kashf qilgan birinchi tajribalardan biri edi. Shundan so'ng u o'sha mashhur tajribaga qaytdi va birlamchi Yerda mavjud bo'lgan deb hisoblangan kimyoviy moddalar aralashmasi orqali elektr toki o'qqa tutilganda, biologik ahamiyatga ega bo'lgan molekulalarning yanada ko'proq diapazoni hosil bo'lishini ko'rsatdi.

Biz bilgan hayot DNK yoki RNKni talab qilishi mumkin, lekin biz bilmagan hayot haqida nima deyish mumkin?

Ammo bu kimyoviy moddalar tirik emas. Faqat ular bir-birlarini ajratish va o'ldirish kabi qiziqarli narsalarni qila boshlaganlarida, biz ularga sharaf beramiz. Xo'sh, kimyoviy moddalarning hayotga sakrashi uchun nima kerak? Badaning javobi hayratlanarli.

"Axborot molekulalarining nomukammal replikatsiyasi ham hayotning, ham evolyutsiyaning kelib chiqishini belgilab bergan bo'lardi va shu bilan tirik bo'lmagan kimyodan biokimyoga o'tardi", deydi Bada. Replikatsiyaning boshlanishi, xususan, xatolarni o'z ichiga olgan replikatsiya turli darajadagi qobiliyatlarga ega bo'lgan "nasl" ni yaratishga olib keladi. Bu molekulyar avlodlar keyinchalik omon qolish uchun bir -biri bilan raqobatlasha oladi.

"Bu, asosan, molekulyar miqyosda Darvin evolyutsiyasi", deydi Bada.

Ko'pgina kimyogarlar uchun, bu replikatsiya va ndash jarayonidir, bu hayotni aniqlashga yordam beradigan biologik hujayralar va ndashning yordami bilan. Axborot molekulalari &ndash DNK va RNK &ndash replikatsiyani ta'minlaydi, ular ham hayotning muhim xususiyati ekanligini ko'rsatadi.

Ammo hayotni o'ziga xos kimyoviy moddalar bilan tavsiflash katta rasmni qabul qila olmaydi. Biz bilgan hayot DNK yoki RNKni talab qilishi mumkin, lekin biz bilmagan hayot haqida nima deyish mumkin?

Astrobiologlar: g'alati musofirlarni ovlash

Begona hayotning mohiyatini taxmin qilish-bu murakkab ish. Ko'plab tadqiqotchilar, shu jumladan Charlz Kokell va Edinburg universiteti Buyuk Britaniyaning Astrobiologiya markazidagi hamkasblari ekstremal muhitda omon qolishga qodir mikroorganizmlardan quruqlikdagi hayot uchun ishonchli shaxs sifatida foydalanadilar. Ular boshqa joyda hayot har xil sharoitlarda yashashi mumkin deb o'ylashadi, lekin, ehtimol, biz hali ham hayotning asosiy xususiyatlarini saqlab qolamiz.

Sagan begona hayotga uglerodga asoslangan qarashni "uglerod shovinizmi" deb atagan.

"[Lekin] biz ushbu ta'rifdan tashqarida bo'lgan narsani topish imkoniyatiga ochiq fikrda bo'lishimiz kerak", deydi Kokell.

Hatto er yuzidagi hayot haqidagi bilimlarimizdan foydalanib, musofirlarni aniqlashga urinishlar ham chalkash natijalarga olib kelishi mumkin. Masalan, NASA 1976 yilda Viking 1 kosmik kemasi hayot uchun uchta sinov bilan jihozlangan Marsga muvaffaqiyatli qo'nganida, ular hayotning yaxshi ta'rifiga ega deb o'ylagan edi. Ayniqsa, bitta sinov Marsda hayot borligini ko'rsatganday tuyuldi: Mars tuprog'ida karbonat angidrid darajasi yuqori bo'lgani, Qizil sayyora yuzasida yashaydigan va nafas olayotgan mikroblar borligini ko'rsatdi.

Aslida, kuzatuvchilar ajralib chiqqan karbonat angidrid deyarli hamma joyda biologik bo'lmagan oksidlovchi kimyoviy reaktsiyalarning hayajonli hodisalariga bog'liq.

Astrobiologlar bu tajribalardan o'rganmoqdalar va o'zga sayyoraliklarni qidirish mezonlarini toraytirmoqdalar, ammo hozircha bu qidiruv muvaffaqiyatsiz qolmoqda.

Sun'iy hayotning yaratilishi hozirda ilm-fanning to'laqonli sohasidir

Ehtimol, astrobiologlar qidiruv mezonlarini juda cheklamasliklari kerak. Sagan o'zga sayyoralar hayotiga uglerodga asoslangan qarashni "uglerod shovinizmi" deb atagan va bunday qarash yerdan tashqarida mavjud bo'lganlarni qidirishni to'xtatib qo'yishi mumkinligini taxmin qilgan.

"Odamlar o'zga sayyoraliklar kremniyga asoslangan yoki turli erituvchilarga (suvdan tashqari) asoslangan bo'lishi mumkinligini taxmin qilishdi", deydi Kokell. "Hatto erdan tashqari aqlli bulutli organizmlar haqida ham munozaralar bo'lgan."

2010 yilda standart fosfor o'rniga mishyak o'z ichiga olgan DNKli bakteriyalar topilishi ko'plab astrobiologlarni hayajonga soldi. O'shandan beri bu topilmalar shubha ostiga qo'yilgan bo'lsa-da, ko'pchilik hali ham an'anaviy qoidalarga rioya qilmaydigan hayot namoyishlaridan umidvor. Ayni paytda, ba'zi olimlar umuman kimyoga asoslangan bo'lmagan hayot shakllari ustida ishlamoqdalar.

Texnologlar: sun'iy hayot qurish

Bir paytlar ilmiy fantastika saqlanib qolgan, sun'iy hayotning yaratilishi endi ilm-fanning to'laqonli sohasidir.

U hayot nima ekanligini juda keng tushunishga harakat qilmoqda

Bir darajada, sun'iy hayot biologlarni laboratoriyalarda ikki yoki undan ortiq mavjud hayot shakllarining qismlarini birlashtirib, yangi organizmlarni yaratishni o'z ichiga olishi mumkin. Ammo u biroz mavhumroq bo'lishi mumkin.

1990-yillardan boshlab, Tomas Reyning Tierra kompyuter dasturi raqamli “hayot shakllari”ning sintezi va evolyutsiyasini namoyish qilgan paytdan beri tadqiqotchilar hayotni chinakamiga taqlid qiluvchi kompyuter dasturlarini yaratishga harakat qilishdi. Hatto hayotga o'xshash xususiyatlarga ega robotlar yaratilishini o'rgana boshlagan jamoalar ham bor.

Oregon shtatining Portlend shahridagi Rid kollejining sun'iy hayot bo'yicha mutaxassisi Mark Bedau: "Asosiy g'oya - bu nafaqat Yerda mavjud bo'lgan tirik tizimlar, balki barcha tirik tizimlarning asosiy xususiyatlarini sinab ko'rish va tushunishdir", deydi. "Bu hayot nima ekanligini juda keng tushunishga harakat qilmoqda, biologiya esa biz biladigan haqiqiy shakllarga e'tibor qaratadi."

Aytgancha, ko'plab sun'iy hayot tadqiqotchilari o'z tadqiqotlarini asoslash uchun Yerdagi hayot haqida bilganlarimizdan foydalanadilar. Bedau aytadiki, tadqiqotchilar u "PMC modeli" deb ataydigan narsani ishlatadilar va dasturni (masalan, DNK), metabolizmni va konteynerni (masalan, hujayra devori) ishlatadilar. "Shuni ta'kidlash kerakki, bu umuman hayotning ta'rifi emas, balki minimal kimyoviy hayotning ta'rifi", deb tushuntiradi u.

Balki biz muhim deb hisoblagan narsalar haqiqatan ham Yerdagi hayotga xosdir

Kimyoviy bo'lmagan hayot shakllari ustida ishlaydigan sun'iy hayot tadqiqotchilari uchun ularning vazifasi PMC komponentlarining dasturiy yoki apparat versiyalarini yaratishdir.

"Umuman olganda, menimcha, [hayot] ning aniq ta'rifi yo'q, lekin biz maqsad qiladigan narsaga muhtojmiz", deydi Sten Rasmussen, Odense shahridagi Janubiy Daniya universitetida sun'iy hayot yaratish ustida ishlaydi. Butun dunyodan kelgan jamoalar PMC modelining alohida komponentlari ustida ishladilar, uning u yoki bu jihatini namoyish qiluvchi tizimlar yaratdilar. Ammo hozirgacha hech kim ularning barchasini sintetik hayot shakliga birlashtirmagan.

"Bu pastdan yuqoriga jarayon, uni bo'lak-bo'lak qurish", deb tushuntiradi u.

Sun'iy hayot tadqiqotlari, oxir -oqibat, biz kutganlarga mutlaqo begona bo'lgan hayotni qurishi mumkin. Bunday tadqiqot hayotdan nimani tushunganimizni qayta aniqlashga yordam beradi. Ammo tadqiqotchilar hali bu bosqichda emas, deydi Bedau. "Ular hayotning barcha shakllarini belgilash haqida tashvishlanishlari shart emas, balki ular bu haqda pivo ustida gaplashishlari mumkin, lekin ular buni o'z ishlariga kiritishlari shart emas", deydi u.

Faylasuflar: hayot jumbog'ini hal qilishga urinish

Shunday qilib, agar hatto & ndash va yangi hayot qurmoqchi bo'lganlar ham hali ham universal ta'rif haqida qayg'urmasalar, olimlar bir o'ylab topishdan xavotirlanishni bas qilishlari kerakmi? Boulderdagi Kolorado universiteti faylasufi Kerol Kliland shunday fikrda. Hech bo'lmaganda hozircha.

Inson tanish nuqtai nazardan belgilashga intiladi. Ammo asosiy haqiqatlar tanish bo'lmasligi mumkin

"Agar siz zebra yordamida sutemizuvchilar haqida umumlashtirmoqchi bo'lsangiz, qaysi xususiyatni tanlaysiz?" – deb so‘radi u. "Albatta, ularning sut bezlari emas, chunki ularning faqat yarmida shunday bo'ladi. Ularning chiziqlari aniq tanlov bo'lib tuyuladi, lekin bu shunchaki tasodif. Ular zebra sut emizuvchilari emas."

Va hayot bilan ham xuddi shunday. Balki biz o'ylagan narsalar haqiqatan ham Yerdagi hayotga xosdir. Axir, bakteriyalardan tortib shergacha bo'lgan hamma narsa bitta umumiy ajdoddan kelib chiqadi, ya'ni bizning koinotdagi hayot jadvalimizda bizda faqat bitta ma'lumot nuqtasi bor.

Saganning so'zlari bilan aytganda: "Inson tanish nuqtai nazaridan ta'riflashga intiladi. Lekin asosiy haqiqatlar tanish bo'lmasligi mumkin".

Muqobil hayot shakllarini kashf qilmagunimizcha va o'rganmagunimizcha, biz hayot uchun muhim deb hisoblagan xususiyatlar haqiqatda universalmi yoki yo'qligini bila olmaymiz. Sun'iy hayotni yaratish hayotning muqobil shakllarini kashf etishni taklif qilishi mumkin, lekin hech bo'lmaganda qisqa vaqt ichida kompyuterda orzu qilingan har qanday hayot shakli bizning tirik tizimlar haqidagi tasavvurlarimizga qanday ta'sir qilishini tasavvur qilish oson.

Ta'rif aslida yangi hayotni izlashga to'sqinlik qilishi mumkin

Hayotni to'g'ri aniqlash uchun bizga begonalar kerak bo'ladi.

Achinarlisi shundaki, biz musofirlarni kashf etishdan oldin hayot ta'rifini aniqlashga urinish ularni topishni qiyinlashtirishi mumkin. Agar 2020-yillarda yangi Mars roveri Marsning tirikligini tan olmagani uchun to'g'ridan-to'g'ri uning yonidan o'tib ketsa, bu qanday fojia bo'lar edi.

"Ta'rif, aslida, yangi hayotni izlashga to'sqinlik qilishi mumkin", deydi Klelend. "Biz hozirgi kontseptsiyamizdan uzoqlashishimiz kerak, shunda biz hayotni o'zimiz bilmagan holda kashf etishga ochiq bo'lamiz."

Olti milliondan ortiq BBC Earth muxlislariga qo'shiling, bizga Facebookda layk bosing yoki Twitter va Instagramda bizni kuzatib boring.


Turlarni kesib o'tish

Ko'pgina yangi yuqumli kasalliklar inson populyatsiyasiga xuddi COVID-19 kabi kiradi: zoonoz yoki hayvonlar orqali odamlarga yuqadigan kasallik. Faqat sut emizuvchilar va qushlar 1,7 millionga yaqin kashf qilinmagan virus turlarini o'z ichiga oladi deb taxmin qilinadi, bu butun dunyo olimlarini turimizning keyingi pandemiyasi sabab Yerning yovvoyi tabiatini o'rganishga undadi. (Bakteriyalar, zamburug'lar va parazitlar hayvonlardan odamlarga ham o'tishi mumkin, ammo bu patogenlar odatda xostlarni yuqtirmasdan ko'payishi mumkin va ko'plab viruslar turlarni kesib o'tish uchun yaxshi jihozlangan.)

Bir turdan ikkinchi turga muvaffaqiyatli o'tish uchun virus bir qator biologik to'siqlarni bartaraf etishi kerak. Patogen bir hayvondan chiqib, boshqasi bilan aloqa qilishi kerak, keyin ikkinchi uy egasida infektsiyani o'rnatishi kerak, deydi Jemma Geoghegan, Makquari universiteti virusologi. Bu tarqalish hodisasi sifatida tanilgan. Virus yangi xostda do'kon ochgandan so'ng, u o'sha turning boshqa a'zolariga tarqalishi kerak.

Aniq raqamlarni taxmin qilish qiyin, ammo hayvonlardan odamga yuqishning aksariyati birinchi odamdan hech qachon o'tib ketmaydigan o'lik infektsiyalarga olib kelishi mumkin. Stenford universiteti virusologi va kasallik ekologi Doroti Tovarning ta'kidlashicha, yangi virus haqiqatda epidemiyaga sabab bo'lishi uchun "ko'p omillar mos kelishi kerak".

Bu omillarga virus tashuvchi hayvonning odamlar bilan qanchalik tez-tez duch kelishi, virusning tarqalish yo'llari, virus xostdan tashqarida qancha vaqt saqlanishi va virusning inson immunitet tizimini qanchalik samarali buzishi kiradi. Yuqish zanjiri bo'ylab har qanday bosqichdagi ajin patogenning yangi turni yuqtirishga urinishini to'xtatishi mumkin. Hatto zararsiz ko'rinadigan omillar, masalan, o'rtacha yog'ingarchilik yoki mahalliy oziq-ovqat tanqisligi, odamlar va hayvonlarning o'zaro ta'sir dinamikasini o'zgartirishi mumkin.

Virus uchun yuqishning eng qiyin jihatlaridan biri bu patogenlar ko'paytirishi kerak bo'lgan molekulyar mexanizmlarni o'z ichiga olgan yangi xost hujayralariga kirishdir. Bu jarayon, odatda, odam hujayrasining tashqarisida joylashgan molekulaga yopishib oluvchi virusni o'z ichiga oladi - bu kalitni qulfni bosish kabi. Sifat qanchalik yaxshi bo'lsa, patogen hujayraning ichki qismiga kirish ehtimoli shuncha yuqori bo'ladi. SARS-CoV-2, COVID-19 ni keltirib chiqaradigan koronavirus, ACE2 oqsili bilan inson nafas yo'llarining hujayralariga kiradi.

Sayyorning aytishicha, har qanday uy egasi uchun "juda kam sonli patogenlar" uning hujayralariga kira oladi. Biz duch keladigan viruslarning aksariyati hujayralarimizdan chiqib ketadi va oxir -oqibat tanamizdan zararsiz mehmonlar sifatida chiqib ketadi.


Viruslar qanchalik katta?

Virus so'zi zaharli suyuqliklarni tavsiflovchi lotincha so'zdan kelib chiqqan. Buning sababi shundaki, mikroblarni ajratish va tasvirlashning dastlabki shakllari bunday mayda zarrachalarni ushlay olmasdi.

Viruslarning o'lchamlari juda kichik - masalan, kengligi 17 nanometr bo'lgan cho'chqa sirkovirusidan tortib, 2,3 mikrometrli Tupanvirus kabi "virus" ta'rifiga shubha qiladigan yirtqich hayvonlargacha farq qiladi.

Xuddi shunday, ular turli xil oqsillarni o'z ichiga olgan yoki har bir hayot qirolligidagi deyarli har bir turni yuqtirish va ko'paytirishga yordam beradigan qobiq va konvertlar bilan o'ralgan turli xil murakkabliklarga ega.

Viruslarni turli usullar bilan kodlash mumkin. Rotaviruslar, masalan, RNKning ikki zanjiriga asoslangan. Koronaviruslar RNKning bir zanjiriga ega, bu "ijobiy ma'no" dir, chunki u to'g'ridan-to'g'ri yangi oqsillarga aylanishi mumkin. Gripp manfiy RNKga ega, ya'ni oqsil hosil qilishdan oldin unga qo'shimcha transkripsiya bosqichi kerak.

Chechak va gerpes viruslari DNK viruslariga misol bo'lib, mezbonni kirish paytida o'z genomini RNKga ko'chirishga majbur qiladi.

Bu genomlarning o'lchamlari ham turlicha. Eng kattalaridan ba'zilari uzunligi bir milliondan ortiq tayanch juft bo'lishi mumkin. Boshqa tomondan, MS2 deb ataladigan bakteriyalarni yuqtiruvchi RNK virusi 3500 ta asosiy juftlikka ega.

Tabiatda qancha turdagi viruslar mavjudligini aniq bilishning iloji yo'q, chunki tadqiqotchilar tuproq, okeanlar va hattoki osmonda tasniflangan va noma'lum genetik belgilarni izlash uchun yangi vositalardan foydalanishlari sababli ularning soni ortib bormoqda. Taxminiy hisob-kitoblarga ko'ra, Yer yuzasida 100 million turdagi viruslar bo'lishi mumkin.


Viruslar

Muallif: Adenovirus sito, Wikikika tomonidan, jamoat mulki
C Maykl Xogan
Muharrir:
Sidney Draggan
Manba:
Yer entsiklopediyasi

Virus - bu mikroskopik organizm bo'lib, u faqat uy egasi hujayralari ichida ko'payishi mumkin. Aksariyat viruslar shunchalik kichkinaki, ularni faqat an'anaviy optik mikroskop yordamida kuzatish mumkin. Viruslar barcha turdagi organizmlarni, shu jumladan hayvonlar va o'simliklarni, shuningdek bakteriyalar va arxeyalarni yuqtiradi. Hozirgi vaqtda millionga yaqin turli xil viruslar batafsil tasvirlangan, ammo ma'lumki, millionlab turlar bor. [1] Viruslar Yerdagi deyarli barcha ekotizimlarda uchraydi va bu kichik hayot shakllari biologik mavjudotning eng keng tarqalgan turi hisoblanadi.[2] Viruslarni o'rganish mikrobiologiya sohasidagi mutaxassislik bo'lgan virusologiya deb nomlanadi.

Viruslar uglerod aylanishida muhim rol o'ynaydi, ularning okean biokimyosidagi roli mikrobiologik metabolik, shu jumladan parchalanish jarayonlarini o'z ichiga oladi. Aynan shu parchalanish dengiz florasining massiv karbonat angidrid bilan nafas olishini rag'batlantiradi. Bu nafas olish har yili atmosferadan taxminan uch gigaton uglerodni samarali ravishda yo'q qiladi. Shunisi e'tiborga loyiqki, viruslar konstruktiv zamonaviy tibbiyot va nanotexnologiyaning muhim sohasi uchun vosita sifatida ishlab chiqilmoqda.

Viruslar oddiy spiral va ikosahedral shakllardan murakkabroq tuzilmalargacha farqlanadi. Ko'pgina viruslar o'rtacha bakteriyalardan taxminan yuz baravar kichikdir. Hayotning evolyutsion tarixida viruslarning kelib chiqishi aniq emas. Ba'zilar plazmidlardan - hujayralar o'rtasida ko'chib o'tishi mumkin bo'lgan DNK bo'laklaridan, boshqalari esa bakteriyalardan paydo bo'lgan bo'lishi mumkin. Evolyutsiyada viruslar genlarni gorizontal ravishda o'tkazishning muhim vositasi bo'lib, genetik xilma-xillikni oshiradi.

Viruslar va xostlarning evolyutsion munosabatlarining batafsil katalogi mavjud bo'lmasa-da, ba'zi umumiy tavsiflarni berish mumkin. Poksviruslar, papillomaviruslar va tobamoviruslar kabi virusli guruhlarda molekulyar taksonomiya odatda xostlarining genetik munosabatlariga mos keladi.[4] Bu shuni ko'rsatadiki, o'sha virusli guruhlarning mansubligi ularning hozirgi hosilalaridan ancha oldin va aslida bu uchta virusli guruh va ularning xostlari birgalikda rivojlangan. Tobamoviruslar kabi genetik jihatdan yaqin bo'lgan guruhning aniq misollari mavjud, xususan, genetik jihatdan uzoq bo'lgan xost, tobamoviruslar odatda Solanaceae oilasining o'simliklaridan foydalanadi, ammo guruhda orkide va kaktus virusini ham topish mumkin.

Viruslarning genom qismlarini rekombinatsiyasi yanada murakkab jumboqni keltirib chiqaradi, chunki bu hodisalar deyarli evolyutsion zanjirning tasodifiy qismlari. Retroviruslar va luteoviruslar virusli guruhlarga misollar bo'lib, ularda yangi organizmlar paydo bo'lishi uchun ko'p miqdordagi rekombinatsiyalar sodir bo'lgan. Ba'zida bu genom birikmalari tabiiy ravishda, virusli yoki hujayrali bo'laklar yordamida sodir bo'ladi. Ba'zi hollarda, mahsulot genomik qismlarni qayta tashkil etishdan iborat bo'lib, ularni psevdo-rekombinatsiya deb atashadi. G'arbiy ot ensefalovirusi bu oxirgi toifaga ma'lum misoldir.

Taxminan ikki milliard yil oldin viruslar arxeya va bakteriyalar bilan xost munosabatlarini boshlagan bo'lishi mumkin, ammo yerdagi qon tomir o'simliklarning ko'payishi evolyutsiyada juda ko'p virusli organizmlar va yo'llarning portlashini ta'minlagan voqea bo'lgan deb taxmin qilingan.[ 5]

Devid Baltimor virusli xabarchi RNK sintezi usuliga asoslangan oldingi tizimni ishlab chiqdi.[7] Baltimor sxemasi messenjer RNK ishlab chiqarish mexanizmiga asoslanadi. Viruslar oqsillarni ishlab chiqarish va ko'paytirish uchun o'z genomlaridan mRNKlarni replikatsiya qilishlari kerak bo'lsa -da, har bir virusli oilada aniq mexanizmlar qo'llaniladi. Virusli genomlar bitta (s) yoki ikkita zanjirli (ds) bo'lishi mumkin, RNK yoki DNKga asoslangan bo'lishi mumkin va ixtiyoriy ravishda teskari transkriptazani (RT) ishlatishi mumkin, bundan tashqari bitta zanjirli RNK virusi spirali ham sezgi (+) yoki antisens (-) bo'lishi mumkin. ). Bu nuanslar viruslarni yettita Baltimor guruhiga ajratadi.

Ushbu Baltimor tasnifi sxemasi messenjer RNK replikatsiyasi kontseptsiyasiga asoslangan, chunki viruslar oqsillarni ishlab chiqarish uchun genomik kodlash orqali messenjer RNKni hosil qiladi va shu nuqtadan boshlab o'zini ko'paytiradi. Natijada Baltimor guruhlari:
• I: dsDNA turi (misollar: Adenovirus, Herpesvirus, Poxvirus)
• II: ssDNA type (+)sense DNA (example: Parvovirus)
• III: dsRNA type (example: Reovirus)
• IV: (+)ssRNA type (+)sense RNA (examples: Picornavirus, Togavirus)
• V: (−)ssRNA type (−)sense RNA (examples: Orthomyxovirus, Rhabdovirus)
• VI: ssRNA-RT type (+)sense RNA with DNA intermediate to life-cycle (example: Retrovirus)
• VII: dsDNA-RT type (example: Hepadnavirus)

Helix: This group is characterized by single type of capsomer stacked around a core axis to form a helical structure, which may have a central cavity within the helix. This geometry results in rod-shaped or filamentous structures, which may be quite long, flexible, and filamentous or abbreviated and rigid. Most often the core genetic macromolecule is single-stranded RNA bound inside the protein helix by polar interactions between the negatively charged nucleic acid and effective positive charge at the protein surface. Tobacco mosaic virus is a prominent example of a helical virus.
Envelope: In some cases a cell membrane of the host is utilized for encasement of the virus this may be either the external cell membrane or the nuclear membrane. These membranes become the outer lipid bilayer known as a viral envelope. The membrane is studded with proteins coded by the viral genome and host genome the lipid membrane and any carbohydrates present derive exclusively from the host. Influenza and HIV viruses use this strategy.
Icosahedral: These are the main shapes occurring in viruses infecting animal hosts. They have icosahedral or near-spherical geometries with icosahedral symmetry. A regular icosahedron is nature's optimum method of producing a closed shell from identical subunits. Twelve is the minimum number of identical capsomers required for this formation, each capsomer being comprised of five identical subunits. A number of viruses (e.g., rotavirus) have more than 12 capsomers and appear spherical, but reflect the underlying symmetry. Capsomers at the apices are surrounded by five other capsomers and are called pentons. Capsomers on the triangular faces are surrounded by six other capsomers, and are termed hexons.

Complex structures: More complex viral structures may have a capsid that is neither purely helical, nor purely icosahedral, and that may possess such ancillary structures as protein tails or a complex outer wall. Some bacteriophages, including Enterobacteria phage T4, possess a complex structure of an icosahedral head bound to a helical tail that may have a hexagon-shaped base plate with protruding protein tail fibers. Such a tail performs as a molecular syringe, first attaching to the bacterial host, and then injecting the viral RNA or DNA into the host cell.

Replikatsiya

The virus, totally dependent upon its host for reproduction, manifests six essential stages in its life cycle:

  • Attachment is the intermolecular binding between viral capsid proteins and receptors on the outer membrane of the host cell. The specificity of binding determines the host species and cell types that are receptive to viral infection. For example, HIV infects only human T cells, because the surface protein interacts with CD4 and chemokine receptors on the surface of the T cell itself. This mechanism is thought to have evolved to discriminate in favor of those viruses that only infect cells in which they are capable of replication. Attachment to the outer host cell membrane may induce the viral-envelope protein to undergo changes that result in the fusion of virus and host cell membranes.
  • Viral entry is the next step, wherein a virus penetrates the host cell wall. In the case of plant cells, the cell outer membrane is composed of cellulose, such that cell wall trauma must be usually precedent however, certain plant viruses (for example, tobacco mosaic virus) can pass from cell to cell through plasmodesmata, or pore structures. Also, bacteria have significantly strong cell walls. Some viruses have evolved mechanisms that inject their DNA or RNA into a bacterium, with the viral capsid remaining outside.
  • Uncoating is the step in which viral enzymes degrade the virus capsid sometimes host enzymes also play a role in this dissolution, that then exposes the viral genome to the interior of the host cell's chemical factory.
  • Replication is the actual synthesis of (i) the virus messenger RNA (except for the case of positive sense RNA) (ii) synthesis of virus proteins and (iii) assembly of replicated genomic material and subsequent protein binding.
  • Post-translational modification of viral proteins sometimes transpires. For example, in the case of HIV, such a step (often termed maturation) happens once the virus has escaped out of the host cell.
  • Lysis is the final step, in which the host cell dies through the act of its membrane being burst by the viral escape. In some cases the new virus genome becomes dormant in the host, only to come to life at a later time, when the activated virus subsequently lyses.

There are numerous mechanisms by which viruses induce disease in an organism, chiefly depending on the viral taxon. At the cellular level these mechanisms often include cell lysis, the breaking open and subsequent death of the cell. In multicellular organisms, if sufficient numbers of cells die, the whole organism may suffer gross metabolic disruption or even mortality. Although viruses may cause disruption of normal homeostasis, resulting in disease, in some cases viruses may simply reside inside an organism without significant apparent harm. An example, termed latency, is the ability of the herpes simplex virus, which includes cold sores, to remain in a dormant state within the human body.
Pathways of viral attack include respiratory intake, ingestion, body fluid contact, and dermal contact. Each virus may have a different set of attack pathway characteristics, but prevention is difficult due to the microscopic size and ex vivo durability of viruses. The extremely small subcellular scale makes trapping of viruses by masks or filters virtually impossible.

Human diseases caused by viruses include chickenpox, HIV, influenza, Marburg, Ebola, Hanta, avian flu, cold sores, and the common cold. The relative strength of viruses to induce disease is denoted by virulence.

Some viruses can induce chronic infection, such that a virus replicates over the entire remaining life of the host, in spite of the host's defense mechanisms. This syndrome is common in hepatitis B and C viral infections. Those with chronic infections are deemed to be carriers—they are reservoirs of infectious virus as long as they live. For regional populations with a high carrier percentage, the disease is termed endemic.

There are a large number viruses that may manifest only as such superficial effects as fruit blemishing however, crop yield reductions may result or even catastrophic loss of an entire plant population in a local area. Furthermore, control of these viruses may not be economically viable. In many cases viruses affecting vegetation may spread horizontally via third-party organisms, termed vectors, which may be insects, fungi, nematodes, or protozoans. Control of plant viruses usually consists of killing or removal of vectors that transmit the virus or removal of weed populations among crops that are secondary hosts. Plant viruses are ineffective in infecting animals, since their replication is only functional in living plant cells.

Vegetative species exhibit elaborate defense mechanisms to ward off viral attack. One of the most effective defense mechanisms is the presence of resistance (R) genes. Each R gene confers resistance to a particular virus by triggering localized areas of cell death in proximity to the infected cell, which is often visible to the naked eye as large splotches. This phenomenon prevents the viral infection from spreading. An alternative defense is via RNA interference.

A bacteriophage is a virus that attacks a bacterium host, and is one of the most abundant organisms on our planet they are found in soil, ocean water, aerosols, and within animal intestinal tracts. For example, as many as 900 million viruses may occur in one milliliter of seawater, situated in surface microbial matting RNA synthesis.[8] The associated infection rate of marine bacteria may approach seventy percent.

Double-stranded, DNA-tailed bacteriophages comprise approximately 95 percent of the bacteriophages currently known. The major defense tactic bacteria employ is the production of enzymes that kill foreign DNA. These restriction endonucleases cut up the viral DNA that is injected into the host cell.

Bacteriophages, in particular, have a central function in marine ecology and carbon cycling. These organisms are extremely widespread in the world's oceans, sometimes occurring in concentrations as high as 900 million bacteriophages per milliliter. Secondly, they have a very rapid attack and replication cycle, being capable of attaching and injecting genomic material into a host bacterium in a matter of minutes, and achieving genetic replication of new viruses in about 20 minutes. They are capable, therefore, of very rapid rates of multiplication in the marine environment.

Next, it is important to note that bacteriophages are highly correlated with concentrations of sewage. This is due to the presence of such bacteria as E. coli present in untreated sewage. In many world regions, large volumes of untreated sewage are discharged to the oceans. Without the ability of bacteriophages to systematically decompose the resulting high bacteria levels, not only would the bacterial concentrations be very high, but opportunity for enhanced carbon dioxide respiration at the atmosphere/ocean interface would be reduced. The outcome respiration rate for ocean absorption of atmospheric carbon is approximately three gigatons per annum,[9] which is a significant percentage of the fossil fuel combustion input to the atmosphere. Thus, further understanding of these viral processes may be key to grasping the world's carbon balance, and perhaps even making intelligent management decisions to avoid global greenhouse gas buildup.

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How Viruses Work

Once inside the cell, the viral enzymes take over those enzymes of the host cell and begin making copies of the viral genetic instructions and new viral proteins using the virus's genetic instructions and the cell's enzyme machinery (see How Cells Work for details on the machinery). The new copies of the viral genetic instructions are packaged inside the new protein coats to make new viruses.

Once the new viruses are made, they leave the host cell in one of two ways:

  1. Ular tanaffus the host cell open (lysis) and destroy the host cell.
  2. Ular chimchilab oling from the cell membrane and break away (budding) with a piece of the cell membrane surrounding them. This is how enveloped viruses leave the cell. In this way, the host cell is not destroyed.

Once free from the host cell, the new viruses can attack other cells. Because one virus can reproduce thousands of new viruses, viral infections can spread quickly throughout the body.

The sequence of events that occurs when you come down with the flu or a cold is a good demonstration of how a virus works:

  1. An infected person sneezes near you.
  2. You inhale the virus particle, and it attaches to cells lining the sinuses in your nose.
  3. The virus attacks the cells lining the sinuses and rapidly reproduces new viruses.
  4. The host cells break, and new viruses spread into your bloodstream and also into your lungs. Because you have lost cells lining your sinuses, fluid can flow into your nasal passages and give you a runny nose.
  5. Viruses in the fluid that drips down your throat attack the cells lining your throat and give you a sore throat.
  6. Viruses in your bloodstream can attack muscle cells and cause you to have muscle aches.

Your immune system responds to the infection, and in the process of fighting, it produces chemicals called pirogenlar that cause your body temperature to increase. Bu isitma actually helps you to fight the infection by slowing down the rate of viral reproduction, because most of your body's chemical reactions have an optimal temperature of 98.6 degrees Fahrenheit (37 degrees Celsius). If your temperature rises slightly above this, the reactions slow down. This immune response continues until the viruses are eliminated from your body. However, if you sneeze, you can spread thousands of new viruses into the environment to await another host.


1599, in the meaning defined at sense 4

Middle English, "pus, discharge from a sore, semen," borrowed from Latin vīrus (neuter) "venom, poisonous fluid, acrid element in a substance, secretion with medical or magical properties," going back to an Indo-European base *u̯is-/*u̯īs- "poison, venom," whence also Middle Irish "venom, poison, evil," Greek īós "poison," Tocharian A wäs and Tocharian B wase, sanskrit viṣáṃ, Avestan viš, viša- (shuningdek vīš?) (sense 1) borrowed from German, borrowed from Latin

Note: The application of Latin vīrus to the submicroscopic infectious agents now considered viruses (rather than to any infectious agent) was apparently first made by the Dutch microbiologist Martinus Beijerinck (1851-1931) in "Ueber ein Contagium vivum fluidum als Ursache der Fleckenkrankheit der Tabaksblätter," Verhandelingen der Koninklijke Akademie van Wetenschappen te Amsterdam, Tweede Sectie, Deel VI, no. 5 (1898). Beijerinck, in studying tobacco mosaic virus, mistakenly believed that the agent was a fluid (contagium vivum fluidum, "living fluid infection") because it passed through filters capable of trapping bacteria. — The neuter gender of vīrus suggests that it was originally an s-stem forms in text other than the nominative and accusative are perhaps found only in Lucretius. The length of the vowel in Latin, Irish, and Greek, in contrast to the short vowel in Tocharian and Indo-Iranian, has been variously accounted for. M. Mayrhofer (Etymologisches Wörterbuch des Altindoarischen) suggests that the etymon was originally a root noun, *u̯īs, *u̯is-ó-, with lengthening of the monosyllabic vowel the daughter languages then generalized one or the other form.


Videoni tomosha qiling: Неклітинні форми життя. Віруси (Yanvar 2023).