Bacterial Structure, Function and Growth I Flashcards
Describe the major structural features of bacteria
1.Cell wall
2.Capsules
3.Flagellum
4.Pili
5.Cytoplasmic membrane
6.Cytoplasm
NO nuclear membrane, ER, mitotic spindle, mitochondira or chloroplasts
Describe the major structural features of bacteria and explain the principal function(s) of each feature: Cell wall
rigid (to resist osmotic lysis and maintaining cell shape), contains peptidoglycan
- characteristic, rigid shape
- –determined by cytoskeletal elements
- —-FtsZ resembles tubulin in eukaryotes
- —-MreB and ParM resemble actin in eukaryotes
- —-CreS appears to function like an intermediate filament protein
- peptidoglycan layer – rigid mesh, surrounds cytoplasmic memb
- –polymer w/ repeating units of 2 hexose sugars + N-acetylglucosamine + N-acetylmuramic acid
- –crosslinking of peptidoglycan chains (greater in gram+ bacteria)
Describe the major structural features of bacteria and explain the principal function(s) of each feature: Capsules
loose gelaninous outer surface layers that usually consist of complex polysaccharides
- enhance virulence (resist phagocytosis)
- most are antigenic
- some used in vaccines (ex. S. pneumoniae and H. influenzae type b)
Describe the major structural features of bacteria and explain the principal function(s) of each feature: Flagellum
appendages originating in the cytoplasmic membrane plthat function as organs of motility
- peritrichous = distributed over the surface
- polar = several at one end or the other
- most are antigenic and chemotactic (“swim” towards it)
Describe the major structural features of bacteria and explain the principal function(s) of each feature: Pili
Long, slender, proteinaceous, antigenic, hair-like structures on the surface of many bacteria
- role in adherence to surfaces and tissues
- Sex pili play a role in bacterial conjugation
Describe the major structural features of bacteria and explain the principal function(s) of each feature: Cytoplasmic membrane
lipid bilayer usually made up to phosphoplipids and protein
- high protein content (60-70%)
- selectively permeable
- uses the electron transport system
Describe the major structural features of bacteria and explain the principal function(s) of each feature: Cytoplasm
aq soln of proteins and metabolites and is the site where metabolic processes occur
- rich in ribosomes (70S) – where protein synthesis occurs, some may be polycistronic
- nucleoid (nuclear body) = where DNA is located
- –tightly coiled DNA
- –no nuclear membrane
- bacterial genome contents
- –chromosome
- –plasmids (extrachromosomal, self-replicating DNA molecules) = often encode virulence factors (R factors carry genes that determine resistance to abx)
- –bacteriophages – viruses that infect bacteria (temperate bacteriophages can integrate into the bacterial chromosomes and replicated as part of those chromosome)
Explain the importance of differences in cell wall structure among bacteria: Gram neg
- a thin, sparsely cross-linked peptidoglycan layer and other major components that are located exterior to the peptidoglycan.
- The outer membrane (OM) is a lipid bilayer (barrier of permeability and protection) that contains lipopolysaccharide (LPS), lipoproteins (which are linked covalently to the peptidoglycan), and porins (which form transmembrane channels permitting diffusion across the membrane of hydrophilic molecules <600 MW), other membrane proteins, and phospholipids
Explain the importance of differences in cell wall structure among bacteria: Gram pos
- have a thick, extensively cross-linked peptidoglycan layer that also contains teichoic acids. -Teichoic acids have a repeating polyglycerol-P or polyribitol-P backbone substituted with other molecules (sugars, aminosugars, D-alanine), and they are covalently attached to the peptidoglycan layer.
- Lipoteichoic acids are attached to the underlying cytoplasmic membrane and help to anchor the cell wall to the membrane.
Draw a typical bacterial growth curve and name each growth phase
- draw this graph por favor
- lag, exponential, stationary, [death]
explain the characteristics of each bacterial growth phase: lag
inoculum period (physiologic adjustment for the starting cells) - induction of new enzymes and the establishment of a proper intracellular environment for optimal growth in the new medium
explain the characteristics of each bacterial growth phase: exponential
rate of increase in cell number/cell mass is proportional to the cell number/cell mass already present. The rate of cell division is maximal for the available nutritional conditions. A constant interval of time (generation/doubling time) is required for doubling of cell number/cell mass. The rate of cell division is maximal for the available nutritional conditions
explain the characteristics of each bacterial growth phase: stationary
essential nutrients are consumed and toxic products of metabolism accumulate. Cell growth may slow dramatically or cease, and growth that occurs is balanced by cell death. Such non-growing or slow-growing cells may exhibit markedly increased resistance to antibiotics such as penicillin or other β-lactam antibiotics that act on growing cells. (In nature, bacteria probably spend most of their time in stationary phase)
explain the characteristics of each bacterial growth phase: death
number of viable bacteria will decrease over time. If autolysis occurs -> decrease in bacterial mass in culture
