Chapters 27 + 33 Microbial Interactions

Symbiosis

Association of one organism with another

Facultative interaction

Microbe has an alternative lifestyle, may or may not do symbiosis with another organism

Obligatory interaction

An interaction that is an absolute requirement

Consortium

a host with more than one symbiont

Consortium can be ____ and _____ or ____

intermittent and cyclic (happens once in awhile) or permanent

Mutualism

Some reciprocal benefit to both partners

Is mutualism obligatory to survive?

To some degree

Microorganism-insect mutualistic relationship

An insect and bacteria coevolve with bacteria as endosymbiont (lives inside)

Protozoan-termite mutualistic relationship

Termite has protist inside it, termite eats wood and protist breaks down lignocellulose in wood to make it usable for both of them. Protozoa may have also have an endosymbiont - nitrogen fixing bacteria

Cooperation

A positive symbiosis that benefits both organisms involved.

Is cooperation obligatory to survive?

No

Bacteria and nematode cooperative relationship

Bacteria and nematode make compounds together that kill butterfly in cocoon. Can live without each other, but do better with.

Commensalism

One organism benefits and the other is neither harmed nor helped

What kind of relationship is commensalism?

Unidirectional

Which organism benefits in commensalism?

Commensal

Commensalism is often

syntrophic

Syntrophic

Cross-feeding - one microbe creates product other can eat or modifies the environment

Examples of commensalism

Nitrification (NH3 —> NO2 —> NO3), microbial succession during spoilage of milk, formation of biofilms

When are biochemical precursors and energy obtained in predation?

After the prey is dead

What uses an epibiotic (lives on surface and sucks blood) mode of attacking prey?

Vampirococcus

What penetrates the cell wall and grows outside the plasma membrane in periplasmic space?

Bdellovibrio

What penetrates the prey then directly consumes the cytoplasmic contents?

Daptobacter

What cells use gliding motility to creep, overtake their prey, and release degradative enzymes to absorb prey nutrients? What kind of predator are they?

Myxococcus, facultative predator “wolf pack”

Some myxococcus are currently being used for

cancer treatment

Parasitism

One organism gains (parasite) and the other is harmed (host) without killing

When are biochemical precursors and energy obtained in parasitism?

While the prey is still alive

There is always some ____ in parasitism

Co-existence in equilibrium

What does parasitism cause and what is an example of this?

genomic reduction, Mycobacterium leprae (mycolic acid)

Competition

When two organisms try to get or use the same resource

Possible outcomes of competition

One dominates or they share the resource

What is a chemical bacteria can make to kill another bacteria?

Colicin

Contact-dependent growth inhibition

Delivers toxin through touch via T5SS and T6SS, negative impact

Vibrio cholerae and Pseudomonas aeruginosa use ___ to ____

T6SS to kill gut microbiota

Ammensalism is

Contact-independent growth inhibition

Ammensalism

One releases compound to negatively impact another

Ammensalism examples

Antibiotic production and bacteriocin production

What is a compound that harms//kills bacteria that look like themselves

Bacteriocin

Example of a bacteriocin

Colicin

Microbiome

All genes found in one’s microbiota

Superorganisms

When gene-encoded metabolic processes of the host become integrated with the microbes (humans)

Probiotics

Live microorganisms, which, when administered in adequate amounts, confer a health benefit to the host.

Synbiotics

Foods or supplements that contain both a prebiotic and a probiotic.

Prebiotic

Food components that beneficial microbes consume to improve gut health.

Germfree Animals (Gnotobiotic)

Animals that are free of all microorganisms, used to study the effects of microbes in a controlled environment.