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Micro Lecture 3: Bacterial Structure and Metabolims
Terms in this set (21)
what color are gram positive and negative bacteria on a gram stain?
Gram Positive: purple. Gram negative: pink
how does gram staining work?
crystal violet penetrates peptidoglycan layer, stains cytoplasm blue
iodine and crystal violet makes complex that can't be washed out of gram positive. complex is washed out of gram negative. Gram negative counter stained with Safranin
what organism is acid-fast?
Mycobacterium (Tb infection)
describe the cell envelope of Gram + and Gram - bacteria
gram positive: cytoplasmic membrane, thick peptidoglycan
gram negative: cytoplasmic membrane, thin peptidoglycan, outer membrane.
what is the function of the cell wall?
gives shape and resistance to osmotic changes
what is the cell wall made of? describe the structure
dissacharide pentapeptide subunits. Disaccharides are N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). cross-links between NAMs
What are the differences in the cell wall structure between Gram + and -(specifically the molecular structure)?
Gram +: pentaglycine between lysine and D-ala
Gram-: direct link between D-ala and diaminopimelic acid (DAP)
what do Beta-lactams target? Give an example
Peptide bridge. Penicillin is incorporated into cell wall b/c it resembles D-ala intermediate. Interferes with formation of D-ala and Lys or DAP bond.
what are teichoic and lipoteichoic acids?
they provide strength to the gram positive cell wall. Also associated with inflammatory repsonse in some Gram + infections
what is the outer membrane?
only in Gram negative bacteria, composed of LPS and phospholipids.
important virulence factor (esp. for Septic shock)
what is LPS of the outer membrane in gram negative organisms composed of?
1. O antigens: repeating sugar residues. used for bacterial typing
2. core sugars
3.Lipid A: fatty acid moieties. bioactive portion
only in gram - bacteria.
Space between inner and outer membranes. contains peptidoglycan.
has enzymes that degrade antibiotics
what are the function of the cell wall in bacteria?(5 functions)
1 transport solutes
2 house enzymes involved in outer membrane and wall synthesis
3 assembly and secretion of extracytoplasmic and extracellular substances
4 generate ATP
5 molecular sensors that monitor environment
describe a bacterial capsule
1. composed of high molecular weight polysaccarides or AAs.
2. has important virulence factors: protect from complement
3. located outside of peptidoglycan/outer membrane
describe Pili (fimbriae)
1. hair like structure, extend from cell membrane
2. composed of pilin and adhesins
3. virulence factors
4. may be common or sex pili
1. helical filaments extend from cell body.
2. involved in motility
3. composed of flagellins: highly antigenic
whats an endospore? 2 examples of organisms who make them?
resting phase of bacteria. Bacillus and Clostridium
Describe 3 types of secretion
type 1: uses a pore. bypasses periplasm. e.g hemolysin in e.coli. uses ABC transporters. gram neg. only
type 2: Sec-dependent. secreted into periplasm in gram negative, extracellular in gram positive. pores formed by secretins.
type 3: secretion in gram negative. contact dependent. injected directly into Euk. cells. e.g yesinia pestis (Plague)
What are the 3 respiratory pathways for bacteria and give examples?
1. aerobic: terminal acceptor is O2. e.g. Mycobacteria
2. anaerobic: use fermentation with terminal oxygen receptor other than O2. e.g clostridia
3. Facultative: can use aerobic or anaerobic (w/ no O2) e.g E. Coli
what are some lab test used to ID bact. based on metabolism?
catabolism of different sugars to produce acid
H2S production detected as gas or FeS
Oxidase test: Cyt c
what are 2 different growth requirement classifications of bacteria?
1. Capnophilic: organism requires CO2 at level exceeding that of air
Microaerophilic: requires O2 at level below that found in air
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