Lecture 12 - Microbe-Microbe Interactions Flashcards by Valerie Solinap

In terms of microbe-microbe interactions, what can change the interactions between species from (for example) commensalism to syntrophism?

changing the conditions of the environment

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What are the 3 characteristics of microbe-microbe interactions?

complex, dependent on organisms, specific environment is important

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What are the 4 positive cell-to-cell interactions?

(CMSS) = commensalism, syntrophism, symbiosis, mutualism

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What are the 4 negative cell-to-cell interactions?

(CPAP) = competition, predation, antagonism, parasitism

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What is neutralism?

no interaction, neither species are affected but live at same area

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What is mutualism/symbiosis?

interaction is needed to survive in the habitat and specific species are required; both species benefit

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What is syntrophism (synergism)?

growth of one is improved by another and both species benefit | basically working together

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What is commensalism?

one benefits and the other is not harmed nor helped

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What is competition?

organisms in the environment fight over limiting nutrient, both species are potentially harmed

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What is parasitism/predation?

host is usually harmed while other is benefited

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What is amensalism (antagonism)?

bacteria and fungi produce chemicals that inhibit the growth of other microorganisms

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What is an example of mutualism and symbiosis interactions? Name 2 discussed.

Lichens, mycorrhizae, root nodules AND bacteria associated with insects

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What is an example of syntrophism interactions? Name 2 discussed.

interspecies hydrogen transfer and cross-feeding of acetate between bacterial species

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What is an example of commensalism interaction? Name 1 discussed.

nitrification — with Nitrosomonas and Nitrobacter&raquo_space; NH3 = NO2 = NO3

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What is an example of competition interaction? Name 1 discussed.

Soil bacteria compete with fungi for nutrients

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What is an example of parasitism/predation interaction? Name 1 discussed.

Bdellovibrio require gram– bacteria host for growth

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What is an example of amensalism interaction?

when end products of a species’ metabolism inhibit the growth of another species (ie antibiotics)

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Explain the symbiotic relationship between diatoms and cyanobacteria. Who provides what?

Diatoms turn CO2 into sugars via photosynthesis for cyanobacteria IN TURN cyanobacteria fix N2 into NH3 for diatom

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How do cyanobacteria infect other diatoms?

reinfection with cyanobacteria = rare so they are inherited vertically

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Where are the cyanobacteria located on the diatoms?

Can exists intracellularly or extracellularly on the diatom

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Where are cyanobacteria more stably located on the diatoms and why?

intracellularly because if extracellularly, they would be easily knocked off the diatom

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Explain the mutualistic relationship between cyanobacteria and fungi. Who provides what?

fungi provides UV protection to the cyanobacteria IN TURN cyanobacteria photosynthesizes for the gungi

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What is a lichen and where are they usually found?

the result of the interaction between fungi and cyanobacteria; they live in harsh environments where neither symbiont can survive alone

What is one way where the relationship between cyanobacteria and fungi is not mutualistic and why?

cyanobacteria can exist without the fungus (doesn’t need it) AND it is destroyed whenever the fungus obtain its nutrients (more parasitic)

What is Geobacter?

organism capable of using acetate to make CO2 and then can shuttle electrons to other organisms | lives in anaerobic environments

Where is acetate found?

anaerobic environments, it is the product of fermentation

What are the 2 organisms that Geobacter has a syntrophism relationship with (separately)?

Methanosarcina and Thiobacillus

What is Methanosarcina?

methanogen

What is Thiobacillus?

a de-nitrifying organism

Explain the syntrophic relationship between Thiobacillus and Geobacter. Who benefits what?

benefits to Geobacter are unknown but give electrons to thiobacillus so it can turn NO3 into NH3

Explain the syntrophic relationship between Methanosarcina and Geobacter. Who benefits what?

benefits to Geobacter are unknown but give electrons to methanosarcina so it can turn CO2 into methane

How can you study if 2 organisms have a syntrophic relationship?

co-culture them and observe effects on growth when one organism is removed and when a nutrient is removed

How can you test to observe a neutralistic relationship in the environment? Can you?

difficult/impossible to show that 2 species have no effect on each other

In what situation where a neutralistic relationship would be plausible?

may occur in the early colonization of an environment until the population density increases enough to produce an effect on each other

In a commensalism relationship, can you prove that one species does not benefit from the other?

hard to prove that there is no effect

What were the 3 types of competition discussed?

competitive exclusion, niche partitioning (space or resources), continued aggression

What is the "competitive exclusion" type of competition?

one species is a better competitor than the others so it will begin to exclude other organisms and end up with a monoculture

What is the niche partitioning type of competition based on space?

a mix of species that overtime will sort into and occupy a different area within a space

What is the niche partitioning type of competition based on resources?

if organisms are not utilizing the same resources = not much competition

What is the continued aggression type of competition?

microbes can produce antibiotics and toxins that target other microbes | overtime targeted microbes evolve defense mechanisms and in turn, the other microbes will counteract those mechanisms = continued aggression

What is the trend with competitive exclusion in terms of diversity, ecological stability and competition over time?

diversity and competition = decrease | ecological stability = increase and plateau

What is the trend with niche partitioning based on space in terms of diversity, ecological stability and competition over time?

competition and diversity = decreases | ecological stability = increases and plateaus

What is the trend with niche partitioning based on resources in terms of diversity, ecological stability and competition over time?

diversity remains high | competition = low | ecological stability = increases

What is the trend with continued aggression in terms of diversity, ecological stability and competition over time?

competition = increases | diversity = decreases | ecological stability = remains very low

What are the 2 types of predation?

facultative and obligate predators

What are facultative predators?

can choose to be a predator if the situation calls for it (not always a predator)

What are obligate predators?

preying on another microbial cell is part of their life cycle and need to in order to survive

Which predator microorganism are the only ones with motility?

gram– members

Name the 3 different phenotypes of predation.

cytoplasmic, periplasmic, epibiotic

What is the cytoplasmic phenotype of predation? What organism is an example of this?

predator breaks through host cell wall and grows in the cytoplasm, eats nutrients in the cytoplasm | daptobacter

What is the periplasmic phenotype of predation? What organism is an example of this?

predator grows in the cytoplasm | Bdellovibrio

What is the epibiotic phenotype of predation? What organism is an example of this?

predator survives on microbe's surface and sucks out nutrients from the cell | vampirococcus

What is the bdellovibrio life cycle (sequence of events)?

Bdellovibrio releases enzymes to degrade and make a hole on cell wall >> gets through and enters periplasmic space; grows and uses nutrients from cytoplasm >> cell lysis and dies = release of all predatory bacteria

What is continued reactivity?

bacteria evolving resistance mechanisms against a species that's targeting them

What are 3 different resistance mechanisms can a bacteria evolve into using?

antibiotic-degrading enzymes, preventing entry of antibiotic, transport systems to that get antibiotic out

What are 2 detrimental produces/activities a species can use against another species in an amensalism interaction?

bacteriocin and metabolic-end-products (chemicals)

What are bacteriocins?

specialized version of an antibiotic that creates holes on plasma membrane of target cells