Topic 3A.4 Prokaryotic Cells

peptidoglycan

a large, net-like molecule found in all bacterial cell walls made up of many parallel polysaccharide chains with short peptide cross-linkages

capsule

a layer formed from starch, gelatin, protein or glycolipid, found around the outside of some bacteria

pili

thread-like protein projections found on the surface of some bacteria

bacteriophage

virus that attacks bacteria

flagella

many-stranded helices of the contractile protein flagellin found on some bacteria; they move the bacteria by rapid rotations

mesosomes

infoldings of the cell membrane of bacteria

nucleoid

the area in a bacterium containing the single circular loop of coiled DNA

plasmids

small, circular pieces of DNA that code for specific aspects of the bacterial phenotype

Gram staining

a staining technique used to distinguish types of bacteria by their cell wall

Gram-positive bacteria

bacteria that contain teichoic acid in their cell walls and stain purple/blue with Gram staining

teichoic acid

a chemical substance found in the cell walls of Gram-positive bacteria

Gram-negative bacteria

bacteria that have no teichoic acid in their cell walls; they stain red with Gram staining

cocci

spherical bacteria

bacilli

rod-shaped bacteria

spirilla

bacteria with a twisted or spiral shape

vibrios

comma-shaped bacteria

obligate aerobes

organisms that need oxygen for respiration

facultative anaerobes

organisms that use oxygen if it available, but can respire and survive without it

obligate anaerobes

organisms that can only respire in the absence of oxygen and are killed by oxygen