L28 (Prokaryotes) Key Terms

peptidoglycan

a type of polymer in bacterial cell walls consisting of modified sugars cross-linked by short polypeptides

gram-positive

bacteria that have a cell wall that is structurally less complex and contains more peptidoglycan than a gram-negative bacteria

gram-negative

bacteria that have a cell wall that is structurally more complex and contain less peptidoglycan than gram-positive bacteria

gram stain

staining method that distinguishes between two different kinds of bacterial cell walls

capsule

in many prokaryotes, a dense and well-defined layer of polysaccharide or protein that surrounds the cell wall and is sticky, protecting the cell and enabling it to adhere to substratres/other cells

endospores

a thick-coated, resistance cell produced by some bacterial cells when they’re exposed to harsh conditions

fimbriae

short, hairlike appendage of a prokaryotic cell that helps it adhere to the substrate/other cells

pili

a structure that links one cell to another at the start of conjugation

taxis

an oriented movement toward/away from a stimulus

nucleoid

non-membrane-enclosed region in a prokaryotic cell where its chromosome is located

plasmid

small circular double-stranded DNA molecule that carries accessory genes separate from those of a bacterial chromosome

transformation

change in genotype and phenotype due to assimilation of external DNA by a cell

transduction

process in which phages carry bacterial DNA from one bacterium to another

conjugation

direct transfer of DNA between two cells that are temporarily joined

F Factor

DNA segment that confers ability to form pili for conjugation and associated functions required for the transfer of DNA from donor to recipient

F plasmid

plasmid form of F factor

R plasmid

a bacterial plasmid carrying genes that confer resistance to certain antibiotics

obligate aerobes

an organism that requires oxygen for cellular respiration and cannot live without it

facultative anaerobes

an organism that makes ATP by aerobic respiration if oxygen is present but switches to anaerobic respiration or fermentation if oxygen isn’t present

obligate anaerobes

an organism that carries out only fermentation or anaerobic respiration (may be poisoned by oxygen)

biofilms

surface-coating colony of one or more species of unicellular organisms that engage in metabolic cooperation

extremophiles

an organism that lives in environmental conditions so extreme few others can live there

halophiles

an organism that lives in a highly saline environment

thermophile

organism that thrives in hot environments

methanogens

organism that produces methane as a waste product of the way it obtains energy

decomposers

organism that absorbs nutrients from nonliving organic material and converts them to inorganic forms

exotoxins

toxic protein that is secreted by prokaryote or other pathogen that produces specific symptoms

endotoxins

a toxic component of the outer membrane of certain gram-negative bacteria that is released only when the bacteria die

bioremediation

the use of organisms to detoxify and restore polluted and degraded ecosystems