细胞生物学 第二章 细胞生物学基本知识

第二章细胞生物学基本知识— 非细胞形态的生命体蛋白粒子(朊病毒)类病毒20世纪20年代英国的一种马铃薯病和相继出现的很多靠传统方法找不到病原体的植物病。70年代，发现是比病毒还小的、单链的、线形的或环状的裸露的RNA。一般是由300多个核甘酸构成的RNA3病毒爱滋病毒流感病毒等—病毒大肠杆菌噬菌体T-4噬菌体爱滋病毒Human

Immunodeficiency

Virus

(AIDS)Rhinovirus

(Common

Cold)Filovirus

(Ebola,

Hemorrhagic

Fever)Influenza

Virus

(Flu)2真细菌细菌1古细菌二古细菌1Symbiont

from

the

Deep:

Microbes

in

Tube

Worms

fromDeep

Sea

Thermal

VentsMicrobe

Name:

not

yet

knownIMAGE

CREDIT:

Colleen

CUniversity古细菌出现于38亿年以前的生命诞生之初.那时的地球,大气中充满了有毒气体(比如硫化氢:H2S),完全没有氧气(即使有那么一点,也会与其它物质反应而被消耗),大气的化学性质是呈还原性的.在这样奇特的环境影响下,古细菌形成了严格厌氧的特性.在30多亿年前的地球上繁荣的生长着.这一下就是10亿多年.终日沸腾的温泉成了古细菌最后的天堂Not

so

inhospitable

:

It

used

to

be

unthinkable

that

lifeexist

at

temperatures

near

boiling,

but

some

intrepidarchaeans

thrive

under

these

conditions.

Geysers,

like

thshown

above,

are

home

to

such

microbes

and

may

help

usunderstand

how

life

existed

when

the

Earth

was

young.FindingArchaea

:

Thehot

springs

ofYellowstoneNational

Park,USA,

wereamong

the

firsplaces

Archaeawere

discovereAt

left

isOctopus

Springand

at

right

isObsidian

Pool.Each

pool

hasslightlydifferent

mineral

content,

temperature,

salinity,

etc.,so

different

pools

may

contain

differentcommunities

of

archaeans

and

other

microbes.The

biologists

pictured

above

are

immersing

microscope

slidesboiling

pool

onto

which

some

archaeans

might

be

captured

for

sSalt-lovers

:

immense

bloom

of

a

halophilic

("salt-loving"

archaean

species

at

a

salt

works

near

San

Quentin,

Baja

Calif

Norte,

Mexico.This

archaean,Halobacterium,

alsolives

in

enormousnumbers

in

salt

pondsat

the

south

end

of

SaFrancisco

Bay;interested

residentsthis

area

should

takethe

Dumbarton

Bridgefor

the

best

views.美国的黄石公园,那里最著名的景观便是间歇泉与泉水中五颜六色的细菌群。它们是地球上最古老的生命形式。古细菌对氧气可是“退避三舍”，哪怕只那么一丁点氧分子就让它们一命呜呼。它们的大多数同伴在20亿年前地球上首次出现氧气时灭绝了，史称“氧的大屠杀”。唯有那么一点点幸存者在其他生物都不敢涉足、几乎没有溶解氧气的少数温泉中繁衍生息。它们能氧化硫化氢、硫黄和其他硫化物为硫酸，并利用这类氧化作用释放的能量来同化二氧化碳。同时，在它们体内累积硫黄粒。使它们带上不同的颜色，如上图。河流中的黄色物质都是古细菌群，当然还有一些硫细菌（Mathanobacillus），它们不属于古细菌。生活在温泉中的古细菌)Basic

Archaeal

Shapes

:

At

far

left,

Methanococjanaschii,

a

coccus

form

with

numerous

flagellaeattached

to

one

side.

At

left

center,

Methanosarbarkeri,

a

lobed

coccus

form

lacking

flagellae.

Acenter,

Methanothermus

fervidus,

a

short

bacillwithout

flagellae.

At

far

right,

Methanobacterithermoautotrophicum,

an

elongate

bacillus

form.Basic

Archaeal

Structure

:

The

three

primary

regions

of

an

cell

are

the

cytoplasm,

cell

membrane,

and

cell

wall.

Above,

three

regions

are

labelled,

with

an

enlargement

at

right

of

tmembrane

structureArchaeal

cell

membranes

are

chemically

different

from

all

living

things,

including

a

"backwards"

glycerol

molecule

isoprene

derivatives

in

place