Bacteria past Questions

distinguish between facultative anaerobic and obligate anaerobic

• FA can grow in the presence or absence of oxygen

• OA can’t tolerate oxygen and die in its presence

• FA rely on aerobic respiration

• OA rely on fermentation or anaerobic respiration

• FA - E coli

• OA - Clostridium botulinum

what role does the human microbiota play in the immune system?

• provides a first line of defense against invading pathogens

• it produces substances that inhibit pathogens

• contributes to the integrity of the intestinal barrier which prevents pathogens from invading the body

an example of a disease that develops as a result of the disruption of the microbiota?

• CDI - clostridium difficile infection

• causes inflammation of the colon (colitis)

• primary trigger is antibiotic use

what is the bacterial capsule?

• protective outer layer composed of polysaccharides that surrounds the cell wall of some bacteria

why is the bacterial capsule considered to be a virulence factor

• inhibit the ability of immune cells by providing a physical barrier and prevents direct contact

• can enhance the bacterium to adhere to host tissues which is needed for the spread of infection

describe two mechanisms of acquired antibiotic resistance in bacteria and an example of each

• Enzymatic degradation - some bacteria produced enzymes that inactivate or modify antibiotics which render them ineffective. This occurs through gene transfer or mutation

  Example = Beta-lactamases

• Altered target sites - bacteria can acquire mutations or genetic changes that alter the target sites where antibiotics exert their effects which prevents the drug from binding effectively

  Example = MRSA (Methicillin-resistant Staphylococcus aureus)

distinguish between thermophilic, mesophilic and psychrophilic bacterial cells

• thermophilic bacteria thrive at elevated temperatures (45-80)

  Their enzymes and membrane lipids remain stable at high temp

  Found in geothermal environments such as hot springs

• Mesophilic bacteria grow best at moderate temperatures (20-45)

  Can thrive in many environments including human and animal bodies, soil and surface waters

• Psychrophilic bacteria grow best at low temperatures (0-20)

  contain antifreeze proteins and membranes that remain fluid at low temp

  Found in cold environments including polar ice capes and deep sea waters

define aerotolerant bacteria growth

• type of anaerobic bacteria that can tolerate the presence of oxygen but no not need it for growth

• rely on fermentation processes to metabolize substrates and produce energy

define microaerophilic bacteria growth

• group of microorganisms that require a reduced level of oxygen for growth, between 2% to 10% oxygen concentration

• high concentrations are toxic to them

what is a bacterial endospore? Example of endospore-forming bacterial species

• highly resistant, dormant structure formed by some bacteria to survive harsh environmental conditions

• they can withstand extreme temperatures, radiation and chemical disinfectants which allow them to endure unfavorable conditions and resume growth when the environment becomes favorable again

• Examples - Bacillus subtilis and Bacillus anthracis

distinguish between sterilization and disinfection

• sterilization is the process of completely eliminating all microorganisms which includes bacteria. fungi, viruses and spores

• methods of sterilization is autoclaving, radiation and chemical agents

• Disinfection is the process of reducing pathogenic microorganisms

• methods of disinfection is heat, ultraviolet and chemical disinfectants

describe the bacterial structure fimbriae in relation to virulence factor

• hair like appendages found on the surface of many bacteria

• some are involved in adhesion to host cells

• increase the pathogenicity of bacteria

describe filtration as a method of sterilization

• a process by which microorganisms are removed from a substance based on their size

• passage of liquid or gas through a screen-like material with pores small enough to retain microorganisms