lecture 2b: Cell walls of Bacteria and Arcaea

Functions of the cell wall

prevents osmotic lysis, blocks large hydrophobic toxins, helps cell shape, aids pathogenicity

The peptidoglycan backbone alternates ______ and ______

NAG; NAM

lysozyme cuts?

glycosidic bond between NAG and NAM

Peptide cross-links use lysine or ______

diaminopimelic acid (DAP)

S. aureus (G+) has an interbridge of ______ and E.coli (G-) ___

5 glycine residues; has no interbridge

Gram-positive walls are up to ~______% peptidoglycan and contain ______ acids

90; teichoic

Lipoteichoic acid

teichoic acid covalently bound to membrane lipids

Proks that lack a cell wall: Mycoplasma strengthen their membrane with ; Thermoplasma uses ______

sterols; lipoglycans

The gram-negative wall is only ~% peptidoglycan; most of it is the ______

10; outer membrane (LPS layer)

what are the parts of the LPS

O-polysaccharide, core polysaccharide, anchored by lipid A

Endotoxin is ______

lipid A

Periplasm

The space between the inner and outer membranes of gram-negative bacteria

is this gram positive or negative

Gram positive

is this gram positive or negative?

negative

Porins

channels letting hydrophilic, low-molecular-weight substances through the outer membrane

Gram-positives keep crystal violet because the thick PG ______ in alcohol and the pores ______

dehydrates; close

Gram-negatives are counterstained with ______

safranin

Pseudomurein

PG-like polymer of NAG and N-acetyltalosaminuronic acid; in some methanogens; lysozyme-insensitive

S-layer

protein or glycoprotein paracrystalline layer; the most common archaeal wall type

Archaea resist lysozyme and penicillin because they lack ______

peptidoglycan