microbial interactions Flashcards
define symbiosis
the stable association of one organism with another
list 3 beneficial interactions between organisms
mutualism, cooperation, commensalism
list 4 harmful interactions between organisms
predation, parasitism, amensalism, competition
in a symbiotic relationship, what is the smaller organism called
the symbiont
in a symbiotic relationship, what is the larger organism called
the host
list 3 ways in which a host may acquire a symbiont
horizontally, vertically, or from the environment
T or F: symbiotic relationships are always temporary
false; they may be stable or temporary
what is the term for a symbiont that lives within the host
endosymbiont
what is the term for a symbiont that lives on the surface of the host
ectosymbiont
list 4 things in a host that a symbiont may alter
health, behavior, reproductive success, evolution
list the 3 types of microbe interactions
microbe-plant, microbe-microbe, microbe-animal
list the three types of microbe-plant interactions
commensalistic, mutualistic, parasitic
what is the name for microbes that live on the surface of plants
epiphytes
what is the name for microbes that colonize internal tissues of plants
endophytes
what is the name for above-ground/aerial portions of plants
phyllosphere
what is the name for the region of the plant surrounding the root
rhizosphere
what is the name for the surface of the root
rhizoplane
roles of microbes in the phyllosphere?
contribute to global C and N cycling, removal of airborne pollutants
what is the term for microbial removal of airborne pollutants
phylloremediation
what is the role of roots
to uptake minerals and water for the plant via root hairs
what do the roots use to uptake minerals and water for the plant
root hairs
describe how root hairs work
apoplastic route is extracellular = materials move along the cell wall
symplastic route causes materials to cross the PM
roots release materials called ___
exudates
how do microbes in the rhizosphere compete with other microbes? (2)
production of antimicrobial agents, production of lytic enzymes
list 2 roles of microbes in the rhizoplane/rhizosphere
provide nutrients for other organisms + promote plant growth
how do microbes enhance plant growth in the rhizoplane/rhizosphere (3)
they produce phytohormones (allows plant to deal with environmental stress), produce compounds that inhibit the growth of plant fungal pathogens, performing nitrogen fixation
list the 3 steps of nitrogen fixation
nitrogen fixation, nitrification, denitrification
describe the steps of nitrogen fixation
nitrogen gas is in the atmosphere. Microbes carry out nitrogen fixation = ammonia (NH3). Ammonia picks up a proton = ammonium (NH4+). Microbes convert it to nitrite = NO2-, then to nitrate = NO3-. Ammonium and nitrite can be used by plants. In denitrification organisms convert nitrate back to nitrogen gas = cycle is complete
T or F: nitrogen fixation is carried out by prokaryotes only (bacteria + archaea)
true
what do symbiotic nitrogen fixers do
they form nitrogen-fixing nodules within the roots of legumes
what is the name for symbiotic nitrogen fixers
rhizobia
describe how Nod factors are produced (during root nodule formation)
plant roots release molecules into the soil and rhizobia bacteria in the soil will respond to these inducing molecules. The inducing molecules attract the bacteria to the root. Bacteria colonize the root hair. The inducing molecule triggers the production of Nod factor signaling compounds from the bacteria.
describe what happens once nod factors are produced (during root nodule formation)
When the Nod factors are picked up by the root hair, it will curl, trapping the bacteria that colonized there. Bacteria then produce a compound that targets the cell wall = invagination of the PM = produces the Infection Thread (tube-like structure). In the infection thread, plant cell division increases the length of the thread. Each bacterium is released into a plant cell and they differentiate into bacteroids and gain the ability to fix N2. Many bacteroids enlarge a root cell = root nodule
what type of reaction is a rhizobium-plant interaction
mutualistic (+/+)
describe why the rhizobium-plant interaction is mutualistic
plant gets ammonium that they can use to make organic molecules + bacteria gets nutrients from the plant
T or F: mutualism is an obligatory relationship = both depend upon each other
true
fungi, called ___, also form mutualistic interactions with plants
mycorrhizae
describe how the fungus and plant benefit from a fungi-plant interaction
plant has greater efficiency to pick up water and minerals from the soil b/c the fungi increases surface area + the fungi gets nutrients
T or F: mycorrhizal fungi are not saprophytic
true
what does it mean that mycorrhizal fungi are not saprophytic
they are not decomposers, instead they get their nutrients from their plant host
list the 2 classifications of mycorrhizae
endomycorrhizae (penetrate into plant root cells) and ectomycorrhizae (stay outside of the plant root cells)
define parasitism
a relationship in which one organism benefits (parasite) and the other is harmed (host)
T or F: in parasitism, the parasite benefits while the host is alive
true
what disease on a plant does A tumefaciens cause
Crown Gall Disease (tumor-like formation)
how is A tumefaciens able to cause disease in plants?
due to the presence of the Ti plasmid (tumor-inducing). When plant tissues become wounded, compounds that attract A tumefaciens are produced, and these compounds activate virulence genes on the Ti plasmid. T DNA is then excised and transferred into the plant cell + T DNA integrates into the plant genome. Then it directs the cell to overproduce phytohormones which cause plant cell proliferation –> tumor and opines are produced
what are opines
used by bacteria as an energy and a carbon course, and they’re a chemoattractant which enhances infection
how can the process of Crown gall disease be used in biotechnology
can be used to produce transgenic plants: take the Ti plasmid, remove T DNA, and replace it with a gene of interest. Put this into a bacterium = recombinant bacterium, then the bacteria can infect plants that carry the gene of interest
what disease does E amylovora cause in plants
fire blight disease
__% of plant diseases are caused by fungi
70%
what plant disease does C purpurea cause
Ergot
what is an ergot
a solid mass that grows on rye. Humans can eat the infected rye = ergotism (hallucinations and convulsions)
what does the tobacco mosaic virus cause in plants
leaf discoloration
define commensalism
a relationship in which the symbiont benefits while the host is neither harmed nor helped
T or F: commensalism can also occur when one microbial group modifies the environment so that it’s better suited for another group
true!
what is syntrophy
a commensalistic relationship when one microbial group has modified the environment in the form of metabolic products that another microbial group can then use
what type of relationship do nitrosomonas sp and nitrobacter sp have
commensalistic + syntrophic. Nitrosomonas aren’t getting anything, but they produce metabolites that nitrobacter can use
describe syntrophy/commensalism in the spoilage of milk
in unpasteurized milk, lactic acid bacteria intially dominate. They will ferment lactose to produce lactic acid. As the pH drops, yeasts and molds begin to thrive/dominate. This will increase the pH, allowing bacillus to grow. Bacillus will digest the protein to form milk coagulates
describe commensalism/syntrophy in biofilmm formation
the first bacteria that colonize a surface make it easier for other bacteria to attach to. Once the biofilm has formed, lots of mutualistic interacts occur
describe commensalism in soil ecosystems
in natural soil ecosystems, groups of organisms in specific niches can modify the environment which makes it more suitable for other groups
how can commensalism in soil ecosystems be illustrated
by generating a Winogradsky column
what is a winogradsky column
a long sealed tube of muddy soil. This column leads to a colourful gradient of different microorganism growth due to the varying levels of oxygen and sulphur inside
define cooperation
both species benefit, but they can survive equally well without the relationship
describe how fungi-motile bacteria is a cooperative relationship + how each one benefits
fungal hyphae can produce a water-lined path into the soil upon which bacteria can travel. Bacteria get nutrients from fungi + fungi get thiamine from bacteria which saves them energy
define amensalism
one organism harms another due to the release of a specific compound
describe the attine ant +Escovopsis fungi relationship
attine ants farm fungi as a source of nourishment, but a parasitic fungus (escovpsis) works against the other fungus
to combat this, the ants coat their body in bacteria (Genus Pseudonocardio) and this bacteria produces a compound that inhibits the growth of the parasitic fungus
the bacteria and parasitic fungus have an amensalistic relationship
define competition
occurs when different organisms within a community are fighting over the same resource. Both are harmed
describe 2 ways in which microbes my compete over an environmental niche
- some secrete compounds into the environment to kill the competitors (contact-independent growth inhibition)
- make use of secretion systems to deliver toxic proteins into the competitor (contact-dependent growth inhibition)
define predation
one organism (the predator) attacks and kills another organism (the prey)
name the two types of predation strategies that predatory bacteria can use
epibiotic predators
endobiotic predators
what does an epibiotic predator do
stay on the outside of the prey + secrete digestive enzymes that degrade the cell wall/PM of the prey = lyses them, and then the predator can use the nutrients
what does an endobiotic predator do
invade the cytoplasm. Once inside, they release enzymes and eat the prey from the inside out. Or they can invade the periplasm
describe how Bdellovibrio bacteriovorus preys on bacteria
it bores through the cell wall and stays in the periplasmic space and takes over the host. Nutrients leak out into the periplasm due to membrane damage. the predator grows into a long filament, the filament separates, the prey is lysed, progeny are released, and the cycle continues
T or F: some predatory bacteria carry out group attack
true
describe how B aphidicola - Aphid relationships are mutualistic
aphid provides a safe habitat and nutrients to the bacterium + the bacterium produces essential amino acids that the aphid doesn’t get out of plant sap. Neither can live on their own
describe how Trichonympha sp - wood eating termite relationship is mutualistic. What two other organisms are involved in the relationship?
bacterium is harboured in the termite’s gut and the protists help the termite to degrade wood. Protists get lots of nutrients and a safe environment
termite requires nitrogen fixing bacteria since wood (cellulose) contains no nitrogen. The nitrogen fixing bacteria live inside the protist and converts glutamine to amino acids that the protist can’t make
protist is also surrounded by spirochetes that help it move within the termite’s gut and help them from being expelled
what is a ruminant? give examples
a mammal with multiple stomach compartments. Ie sheep, camels, giraffe, cow
list the cow stomach compartments in order
rumen, reticulum, omasum, abomasum
describe the mutualistic interactions in the rumen ecosystem
in the rumen, bacteria, archaea, fungi, and protists are present. They all produce different enzymes that help the cow digest plant material
what does the human microbiome do for us
helps to digest food, stimulates immune system, protects against pathogenic organisms, produces vitamins B12, thiamine, riboflavin, K
what type of interaction do humans have with our microbiome
mutualistic
describe how P destructabs - Bat interaction is parasitic
fungi coats the skin of bats = white-nose syndrome = bats starve to death
what does T rubru - Human cause? (parasitic)
athlete’s foot
what does S pyogenes - Human cause? (parasitic)
necrotizing fasciitis
