Medical Microbiology

TheMorphologyandFineStructureofBacteria 153

30 %ofthedrymassofthecellwall.Themembranelipoteichoicacidsare

anchoredinthecytoplasmicmembrane,whereasthecellwallteichoicacids

arecovalentlycoupledtothemurein.Thephysiologicalroleoftheteichoic

TheMureinBuildingBlock

CH 2 OH

O

O O

CH 2 OH

O

O

ONH CO CH^3 NH CO CH^3

OH

CH CH 3

CO

(NH)

L-alanine

D-isoglutamine

L-lysine–[glycine] 5

D-alanine

D-alanine (COOH)

Fig.3. 8 Themurein(syn.peptido-

glycan)ofthecellwalliscomposed

ofaseriesofidenticalsubunits.The

terminalD-alanineissplitoffeach

timeanewcrosslinkissynthesized.

Onlyinstaphylococciisapentagly-

cineinterpeptidebridgeinsertedbe-

tweenadjacentpeptides.

TheStructureofMurein

= N-acetyl muramic acid (= 3-0 lactyl ether of N-acetyl glucosamine)

GlcNAc Mur Mur Mur

Mur Mur Mur Mur

Mur

= N-acetyl glucosamine = Aminosäure

Transpeptidase

NH-CO NH-CO

GlcNAc

GlcNAc

GlcNAc

GlcNAc

GlcNAc

GlcNAc

GlcNAc

Fig.3. 9 SolublemureinfragmentsofGram-negativeandGram-positivebacteria

canstimulateexcessivecytokinesecretioninmacrophagesbybindingtotoll-like

receptorsandCD14.Cytokinescausetheclinicalsymptomsofsepsisorseptic

shocksyndrome(seeunderLipoidA,p. 1 56).

3

Kayser, Medical Microbiology © 2005 Thieme