Micro: Bacterial Growth and Metabolism Flashcards
The growth rate of a particular organism depends on what 4 factors?
availability of nutrients, environmental pH, salinity and temperature
What are prototrophs?
bacteria that can synthesize all essential metabolites
What are auxotrophs?
bacteria that have acquired mutations that require them to obtain certain essential metabolites from the environment.
True or false, most bacteria are inhibited by acidic pH
True
True of false, high salinity is a common inhibitor of bacterial growth
True
Human pathogens are classified as __________ because they grow optimally between ____ Celsius and ___ Celsius.
Mesophiles; 30-37 Celsius
Bacteria that grow in extreme cold are called:
psychrophiles
Bacteria that can grow in extreme heat are called:
thermophiles
What necessary bacterial nutrient stands out because of its importance to growth and virulence?
Iron
How do bacteria counter iron limitation by the host (sequestration of free Fe)?
By secreting siderophores which chelate Fe and are then actively transported into the bacterial cell
Most bacteria take between ____ and ____ minutes to replicate.
30-60 minutes
The ____ phase of bacterial cell propagation is the period following initial inoculation in which essentially no growth occurs.
Lag phase
Why is there essentially no growth of bacteria during the lag phase?
The bacteria are adapting to the new nutrient environment, reprogramming gene expression to meet new standards.
Following the lag phase, bacterial growth enters the ______ phase, wherein bacteria begin to replicate and establish constant, optimal doubling times.
exponential (log) phase
During which phase of the bacterial growth curve are the bacteria most sensitive to antibiotic therapy and why?
Log phase, because the bacteria experience maximal DNA and protein synthesis.
During which phase of the cell growth curve is the best time to gram stain organisms?
log phase
What are two consequences of log growth that are dependent on the environment to prevent halting bacterial growth?
depletion of nutrients and accumulation of wastes
When the nutrients in a culture’s environment are outstripped by demands and waste products accumulate beyond healthy levels, this area of the bacterial growth curve has been reached.
Stationary phase. The rate of cell division becomes equal to the rate of cell death.
Why is gram staining not ideal during the stationary phase of the bacterial cell growth curve?
Bacteria may begin sporulation (if spore formers) due to the austere environment. The nature of the spore will inhibit or reduce efficacy of gram staining.
As the nutrients deplete and waste increases, the rate of cell death exceeds the rate of cell division and the culture enters the ____ “death” phase.
Decline phase.
Individual, free-living bacteria are also referred to as
planktonic bacteria
Bacteria in a ______ are encased in a protective CHO matrix that is adhesive and only formed after a series of events requiring motility and adhesion of planktonic bacteria
Biofilm
It is estimated that 80% of infections result in the organization of bacteria into this structure that is a source of recurrent infections and treatment failures:
Biofilm
The nature of a biofilm impairs _______ access to the residing bacteria, is anti-_________, and because of its ______ nature, often requires the removal of a infected implanted medical devices.
antibiotic access
anti-phagocytic
adherent nature
In aerobes or facultative anaerobes , respiration occurs where?
Internal face of cytoplasmic membrane
How many ATPs are produced in oxidative respiration in aerobic bacteria?
34
Strict (or obligate) anaerobes use _________, another form of anaerobic respiration, to generate energy and metabolites.
Fermentation
In the absence of oxygen, anaerobic respiration can occur, in which an ______ or ___________ compound other than oxygen serves as the final electron acceptor.
Organic or inorganic compound
During fermentation, _______ is converted to various organic end products (e.g. acetic acid, butyric acid or lactic acid), CO2, or Hydrogen and electrons are directly transferred to ________ acceptors.
pyruvate; organic acceptors
Is fermentation an efficient way to generate energy?
No.
Which is faster, aerobic or anaerobic growth for facultative anaerobes?
Aerobic
Strict aerobes produce 3 enzymes to diffuse the damage caused by the production of superoxide and hydrogen peroxide. Name them.
superoxide dismutase (SOD), catalase, and peroxidase
What are the two enzymes always produced by facultative anaerobes to diffuse the damage caused by superoxide and hydrogen peroxide?
SOD and peroxidase
Strict anaerobes lack this enzyme and are therefore killed in the presence of oxygen due to the accumulation of superoxide anions.
Superoxide dismutase (SOD)
The presence or absence of catalase has this consequence for bacteria:
Patients with chronic granulomatous disease (CGD) lack NADPH oxidase in their neutrophils. Consequently, the neutrophils fail to produce an oxidative “burst”. This allows catalase positive cells such as staphylococci to overcome the basal levels of peroxide and survive, causing recurrent infections.
Bacteria must synthesize _____ acid (a source of nucleotides and methionine) rather than use environmental sources.
Folic acid
These two antimicrobials exploit the bacterial pathway for synthesizing folic acid to kill microbes.
sulfonamides and trimethoprim
Obligate intracellular bacteria are dependent on host cell ______ ________ and ______, and cannot be grown on synthetic media.
nucleotide cofactors; ATP
________ is the mechanism of disease development.
Pathogenesis
_______ is a term expressing degrees of pathogenicity.
Virulence
________ is the presence and multiplication of microorganisms without tissue invasion or damage.
Colonization
______ is colonization that generally leads to disease.
Infection
A disease that rapidly affects many people in a fixed period of time.
Epidemic
_______ ______ is any number of products produced and often secreted by pathogens to invade and cause disease in a host and evade host defenses.
Virulence factor
