Microbiology: Microbial Ecology and Pathogenesis Flashcards

Which term describes the relationship where one organism benefits and the other is neither helped nor harmed?

Answer: Commensalism

Commensalism is a symbiotic relationship in which one partner benefits while the other experiences no significant effect.

A bacterium that can only cause disease when the host's immune system is compromised is classified as a:

Answer: Opportunistic pathogen

Opportunistic pathogens exploit immunocompromised states and do not normally cause disease in healthy hosts.

The term 'Koch's postulates' refers to criteria used to:

Answer: Establish causation between a microbe and a disease

Koch's postulates provide a logical framework for proving that a specific microorganism is the causative agent of a specific disease.

Which of the following best describes a biofilm?

Answer: A structured community of microbes encased in a self-produced matrix

Biofilms are structured microbial communities embedded in an extracellular polymeric substance (EPS) matrix attached to surfaces.

Nitrogen fixation in ecosystems is primarily performed by:

Answer: Certain bacteria and archaea

Prokaryotes such as Rhizobium, Azotobacter, and certain cyanobacteria contain nitrogenase and can fix atmospheric N₂ into usable ammonia.

Exotoxins differ from endotoxins primarily because exotoxins are:

Answer: Secreted proteins produced by living bacteria

Exotoxins are proteinaceous molecules actively secreted by bacteria (both Gram-positive and Gram-negative) and are generally heat-labile.

Which ecological concept describes the role a microorganism plays in its environment, including its resource use and interactions?

Answer: Niche

An organism's niche encompasses its functional role, resource use, and interactions within an ecosystem.