Medical Microbiology

154 3 GeneralBacteriology

acidsisnotknownindetail;possiblytheyregulatetheactivityoftheauto-

lysinsthatsteergrowthandtransversefissionprocessesinthecell.Within

themacroorganism,teichoicacidscanactivatethealternativecomplement

pathwayandstimulatemacrophagestosecretecytokines.Examplesofcell

wall-associatedproteinsareproteinA,theclumpingfactor,andthefibronec-

tin-bindingproteinofStaphylococcusaureusortheMproteinofStreptococcus

pyogenes.Cellwallanchorregionsintheseproteinsextendingfarbeyondthe

mureinareboundcovalentlytoitspeptidecomponents.Cellwall-associated

proteinsfrequentlyfunctionaspathogenicitydeterminants(specificadher-

ence;phagocyteprotection).

ThecellwallofGram-negativebacteria.Here,themureinisonlyabout 2 nm

thickandcontributesupto 10 %ofthedrycellwallmass(Fig.3. 11 ).Theouter

membraneisthesalientstructuralelement.Itcontainsnumerousproteins

(50%bymass)aswellasthemedicallycriticallipopolysaccharide.

TheCellWallofGram-PositiveBacteria

Cytoplasmic

membrane

Cell wall-

associated

proteins

Membrane lipoteichoic acid

Cell wall teichoic acid

Cell wall-specific

polysaccharide

Murein

(syn. peptid-

oglycan)

Fig.3. 10 Notethecharacteristicthickmureinlayer,theproteinsandteichoic

acidsanchoredinthemurein,andthelipoteichoicacidfixedtothemembrane

byalipophilicanchor(nottoscale).

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Kayser, Medical Microbiology © 2005 Thieme