學(xué)姐-微生物課件cell

3.8

Cell

Wall

of

Prokaryotes:

Peptidoglycan

andRelated

Molecules原核生物胞壁:肽聚糖與相關(guān)分子(Fig

4.32

Protoplasts原生(b)

In

a

solution

containing

an

isotonic

concentration

of

a

solutesuch

as

sucrose,

water

does

not

enter

the

protoplast

and

itremains

stable.等滲溶液中,

水不進入原生

,

原生 穩(wěn)定.Shanghai

Jiao

Tong

UniversityWhat

is

a

cell

wall

for?A

wall

is

for

against

pressure-

2

atmA

wall

is

for

maintaining

cell

shA

wall

is

f iving

cells

rigidityShanghai

Jiao

Tong

UniversityGram

stain革蘭氏染色This

staining

method

has

long

beenusedfor

classifying

and

identifying

bacteria(For

more

detail:

Lecture

3-1)Fig

4-4Stepsin

the

Gramstain

procedure.革蘭氏染色過程結(jié)晶紫染1分鐘碘液媒染3分鐘脫色20秒沙黃復(fù)染1-2分鐘FLASHExamples

of

Gram

StainingDifferences

in

cell

wall

structure

are

at

the

base

of

differences

in

theGram-staining

reaction.

The

G-

cell

wall

is

a

multilayered

structure

andquite

complex,

whereas

the

G+

cell

wall

consists

of

primarily

a

singletype

of

molecule

and

is

often

much

thicker.Fig

4.27

Cell

walls

of

BacteriaFLASHShanghai

Jiao

Tong

University4.8.1

Peptidoglycan肽聚糖Cell

wall

of

Bacteria

have

one

rigid

layer

tostrengthen

the

wall.The

rigid

layer

of

G+and

G-Bacteria

ispeptidoglycan

layer.肽聚糖層In

G-

Bacteria,

additional

layers

are

presentoutside

this

rigid

layer.Fig

4.29Peptidoglycan

unit

is

composed

of

two

suger

derivatives,

N-acetylglucosamine

and

N-acetylmuramic

acid,and

a

small

group

of

amino

acidsconsisting

of

L-alanine,

D-alanine,

D-glutamic

acid,

and

either

lysine

ordiaminopimelic

acid(DAP).肽聚糖由N-乙酰葡萄糖胺和-乙酰胞壁酸兩種糖,加上

一組氨基酸組成(DAP:二氨基庚二酸)

(c)

Overall

structure

ofpeptidoglycan.G,

N-acetylglucosamine;M,N-acetylmuramic

acidFig

4-30

How

the

peptide

and

glycan

units

are

connected

to

form

the

peptidoglycansheet.

(a)

No

interbridge

in

gram-negative

Bacteria.

(b)

Glycine

interbridge

ingram-positive

Bacteria.G+菌的肽聚糖單位之間有甘氨酸五肽橋,而G-菌無五肽橋.Shanghai

Jiao

Tong

University4.8.2

The

structure

of

Gram

positive

bacterial

cellwallsOne

thick

peptidoglycan

layer

(25

sheets)Teichoic

acids

（磷壁酸）Polymers

containing

glycerolphosphate

or

ribitolphosphate

residues

含在磷酸甘油及磷酸核糖醇的多聚物L(fēng)ipoteichoic

acids:teichoic

acids

that

covalently

bound

tomembrane

lipids脂磷壁酸:與膜脂類共價連接的磷壁酸Fig.

4.31

Summary

diagram

of

the

gram-positivecellwallThe

cell

walls

of

gram-positive

cells

containmostly

peptidoglycan.The

cell

walls

of

gram-positive

cells

are

smoother

than

that

of

gram-negative

cells.Shanghai

Jiao

Tong

University4.9

The

Outer

Membrane

ofGram

Negative

BacteriaTwo

membranesOuter

membrane外膜Cytoplasmic

membrane細胞質(zhì)膜One

thin

peptidoglycan

layer一層肽聚糖層

One

out

of

cell

bounded

spacePeriplasm

space周質(zhì)空間PorinFig

4.35

The

gram-negative

cell

wall.

Althoughthe

outer

membrane

is

often

called

the

"second

lipidbilayer,"

the

chemistry

and

architecture

of

this

layerdiffers

in

many

ways

from

that

of

the

cytoplasmicmembraneShanghai

Jiao

Tong

UniversityShanghai

Jiao

Tong

UniversityStructure

of

the

lipopolysaccharide

(LPS)

of

G-bacteria.脂多糖?O-specific

polysaccharide

varies

among

species.O-特異多糖?Core

polysaccharide

多糖?Lipid

A

類脂AFig

4.36

Cell

wall

of

G—

bacteria

under

electronmicroscopeFig

4.27

The

surface

texture

of

a

G-

cell

is

heavily

folded

when

compared

with

a

G+

cell.Relationship

of

Cell

Wall

Structure

to

theGramStain

p.81Phenomenon:

In

Gram

stain,

an

insoluble

crystal

violet-iodine

complex

is

formed

inside

the

cell,

and

the

complex

isextracted

by

alcohol

from

G-

but

not

from

G+

Bacteria.Reason:G+Bacteria,which

have

very

thick

peptidoglycanlayer, e

dehydrated

by

the

alcohol.This

causes

thepores

in

the

walls

to

close,preventing

the

insolublecrystalviolet-iodinecomplexfromesca.G+菌的厚肽聚糖層被乙醇脫水,造成壁上小孔收縮,從而使不溶性的結(jié)晶紫-碘復(fù)合物不能洗出.Then,

what

happened

to

G-

Bacteria?Shanghai

Jiao

Tong

UniversityShanghai

Jiao

Tong

UniversityShanghai

Jiao

Tong

UniversityIn

G-

Bacteria,

alcohol

readilypenetrates

the

lipid-rich

outerlayer,

andthe

thin

peptidoglycan

layer

alsodoesnot

prevent

solvent

passage,

thus,thecrystal

violet-iodine

complex

is

easilyremoved.G-菌中,乙醇很容易外膜,薄的肽聚糖壁也無法富脂的溶劑的通過.Shanghai

Jiao

Tong

UniversityHow

can

cell

wallkilling

a

cell?e

theforPeptidoglycan

StructureLysozyme

:-1,4

bond

is

sensitive

to

lysozyme肽聚糖的

-1,4糖苷鏈對溶菌酶敏感PeptidoglycansynthesisPenicillin:The commercialized

and

stillmost

important

antibiotic青霉素Transport

of

peptidoglycan

precursors

was

send

to

the

growing

point

of

thecell

wall