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Flashcards in Bacterial Growth and Metabolism Deck (38)
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bacteria replicate by ___

binary fission


what is binary fission?

one cell divides to yield 2 daughter cells


the growth rate of a particular organism depends on:

availability of nutrients, environmental pH, salinity, and temperature


what are prototrophs?

bacteria that can synthesize all essential metabolites


what are autotrophs?

bacteria with acquired mutations that require them to obtain certain essential metabolites from the environment


most bacteria are inhibited by ___ pH and ___ salt

low (acid); high


why are human pathogens classified as mesophiles?

grow optimally bw 30-37C


other bacteria can grow in extreme cold of heat. what are these called?

psychrophiles and thermophiles


what nutrient stands out as one that greatly impacts the rate of cell division?

iron, important to growth and virulence


why is sequestration of free iron in blood and other body fluids by transferrin and lactoferrin (iron-binding proteins) significant?

defense against infection


Bacterial growth in a liquid (“broth”) culture can be measured by ___

growing aliquots of the culture on agar medium as the aliquots are taken at various times after broth inoculation


bacterial growth can also be followed by measuring the ___ of a liquid culture over time

turbidity; as the bacteria multiply, they cloud the broth which can be visibly seen and measured using a spectrophotometer


the bacterial growth curve includes what phases?

lag, exponential, stationary, decline/death phase


what is happening in the lag phase?

essentially no growth occurs; bacteria are adapting to new nutrient environment, reprogramming gene expression to meet new needs


what is happening in the exponential phase?

establish constant, optimal doubling times; bacteria experience maximal DNA and protein synthesis and are most acutely sensitive to antibiotic therapy; also best time to Gram stain organisms
- exponential growth leads to depletion of nutrients and accumulation of wastes. Metabolism is therefore greatly reduced and rate of cell division becomes equal to rate of cell death


what is happening in the stationary phase?

no net increase in number of viable cells (bacteria become somewhat refractive to antibiotic therapy and Gram positive spore
formers initiate sporulation)


what is happening in the decline phase?

nutrients deplete and waste increases, the rate of cell death exceeds the rate of cell division


what is a biofilm?

bacteria in a biofilm are encased in a protective carbohydrate matrix that is adhesive and only formed after a series of events requiring motility and adhesion of planktonic bacteria


why are biofilms significant?

bc of their prevalence, but also bc they are a source of recurrent infections and treatment failures; impairs antibiotic access to the residing bacteria, is anti-phagocytic, and bc of its adherent nature, often requires the removal of an infected implanted valve


what is the purpose of metabolism?

provide the energy and building blocks a cell needs to survive and replicate


describe oxidative respiration of aerobes and facultative anaerobes?

In the presence of oxygen, aerobes and facultative anaerobes funnel pyruvate through the citric acid cycle and oxygen serves as the final electron acceptor; produces 34 ATP


oxid. respiration occurs where?

internal face of cytoplasmic membrane


describe anaerobic respiration

In the absence of oxygen, an organic or inorganic compound other than oxygen serves as the final electron acceptor


is fermentation an efficient way of generating energy?



what is the major drawback of oxidative respiration?

produces hydrogen peroxide and superoxide anions (toxic to cell)


what enzymes do strict aerobes produce to diffuse the damage caused by production of ROS?

superoxide dismutase, catalase, and peroxidase


what enzymes do facultative anaerobes produce to diffuse the damage caused by production of ROS?

superoxide dismutase and peroxidase; will not always have catalase


what enzymes do strict anaerobes produce to diffuse the damage caused by production of ROS?

catalase and peroxidase, lack superoxide dismutase so die in presence of O2 due to accumulation of superoxide anions


why must bacteria synthesize folic acid?

source of nucleotides and methionine


obligate intracellular pathogens are dependent on the host cell for ____

nucleotide cofactors and ATP