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Chap 23 - symbioses
Microbial Symbioses with Microbes, Plants, and Animals
Question | Answer |
---|---|
what is a symbioses | a microbe that lives with a macroorganism or other microorganisms in long-term relationships |
Symbioses relationships are ___________________ where the interactions benefit both organisms involved | mutualistic |
most microorganisms in symbiotic relationships have coevolved meaning | the organisms have evolved together over time |
what are lichens | leafy or encrusted organisms, formed between the relationship between a fungus and algae (cyanobacterium) |
where are lichens most commonly found | bare rocks, tree trunks, house roofs, and the surfaces of bare soils |
in lichens, what is the benefit of algea | photosynthetic and produces organic matter; algae can also fix nitrogen |
in lichens, what does fungus provide | structure within the phototrophic partner, allows the cyanobacterium to grow protected from erosion and with dissolved inorganic nutrients |
what is consortia? What is their "scientific" name? | microbial mutualisms in freshwater, called Chlorochromatium aggregatum |
Chlorochromatium aggregatum is a mutualist relatioidic lakesnship between | Green sulfur bacteria (epibionts) and flagellated rod-shaped bacteriu, |
what habitat is consortia normally found in | stratified sulfuridic lakes |
describe the metabolism of epibionts | obligate anaerobic phototrophs |
in stratified sulfuridic lakes, epibionts take up ____________________% of the bacterial biomass | 70% |
explain the discovery of consortia | they were discovered over 100 years ago but the details were unknown until modern culture methods and molecular techniques allowed for more detailed studies |
what creates root nodules | mutualistic relationships between legumes and nitrogen0fixing bacteria |
what are the most important symbioses known | root nodule symbioses (between legumes and nitrogen fixing) |
give some examples of leguemes | soybeans, clover, alfalfa, beans, peas, peanuts |
what is the best known bacteria in the root nodule symbiosis | rhizobia |
describe the metabolism of rhizobia | nitrogen-fixing |
what class(es) is Rhizodia part of | Alphaproteobacteria or Betaproteobacteria |
what is the importance of root nodule formation | significant increases in soil nitrogen levels, and accounts for 1/4 of Nitrogen fixed annually on earth |
root nodules grow well in areas where | other plants do not (i.e. nitrogen deficient soils) |
Nitrogen-fixing bacteria need __________ to generate energy for fixing Nitrogen | Oxygen (O2) |
the enzymes that fix nitrogen are called _____________ and are inactivated by ______________ | nitrogenases; Oxygen (O2) |
because the nitrogenase enzyme is inactivated by oxygen molecules; this protein serves as an "oxygen buffer" in root nodules | leghemoglobin |
(not a question) different rhizobial species infect different species of legumes, so the bacteria that infect peas will be different from those that infect clover | |
a cross-inoculation group is | a group of related legumes that can be infected by a particular species of rhizobia |
after infecting a root to form a nodule, the bacteria change shapt and are called ______________ that form a ____________ in the nodule | bacteriods; symbiosome |
what bacterial genes direct the steps in nodule formation | nod genes |
the ______________ gene encodes proteins that produce olidosaccharides called _______________ | nodABC; Nod factors |
what are the functions of Nod factors | induce root hair curling, trigger plant cell dividion, signal legumes to develop root nodule |
___________________ is a positive regulator that is induced by plant flavonoids (colored plant nutrients) | NodD |
in root nodules, what do the plants provide for bacteriods | fuel in the form of pyruvate for nitrogen fixation |
the legume-bacteria symbiosis is characterized by | oxygen sequestration, several metabolic reactions, and nutrient exchange |
what are stem-nodules | nodules that are formed on the stem of plants |
stem-nodules formation is more common in _________________ regions | tropical; where soil is depleted of nutrients and poor in nitrogen due to leaching |
(not a question) nonlegume nitrogen-fixing symbiosis also occurs, but with bacteria other than rhizobia | |
in the water fern _________________ contains a species of heterocyctous nitrogen fixing bacteria known as ________________ | Azolla; Anabaena |
the alder tree (genus __________) has nitrogen-fixing root nodules that harbor the bacterium ________________ in the heterocyst-like structures that are protected from free oxygen | Alnus; Frankia |
mycorrhizae is a mutualistic association of ___________________________ | plant roots and fungi |
in mycorrhizae, the plant benefits from | the transfer of inorganic nutrients from the fungus |
in mycorrhizae, the fungi benefits from the plant | the plant donates carbohydrates to the fungus |
ectomycorrhizae | mycorrhizae remains outside the root; the fungi cells form a sheath around the outside of the root with little penetration |
where would ectomycorrhizae be mostly found | forest trees, particularly boreal and temperate forests |
endomycorrhizae | the mycelium of fungi becomes deeply embedded within the root tissue |
arbuscular mycorrhizae | the name of the deeply embedded mycelium in roots |
(ecto/endo)mycorrhizae is more common | ENDomycorrizae is more common |
>80% terrestrial plant species have this specific form of mutualist relationship | Endomycorrhizae with fungi |
how does mycorrhizal fungi assist plants | improve nutrient absorption; due to greater surface area provided by the fungal mycelium. this helps with plant growth |
this species forms a parasitic symbiosis with plants and causes clown gall disease | Agrobacterium tumefaciens |
what are crown galls | plant tumors produced by A. tumefaciens cells harboring large plasmids (Tumor induction plasmids) |
to initiate tumor formation ... | the A. tumefaciens cells attach to a wound site on the plant |
after A. tumefaciens attach to a plant | they synthesize cellulose microfibrils and transfer a portion of the Ti plasmid to plant cells |
the DNA transfer of Ti cells is mediated by | vir-encoded protiens |
what are some functional uses for the Ti plasmid in the laboratory | for genetic engineering of plants |
for insects, microbial symbionts can be acquired in two ways _________________ | horizontal transmitting (from the environment) or vertical/heritable transmitting (parent to child) |
in heritable symbionts, insects are ____________ (meaning that they lack a free-living replicative stage) | obligateand protection from pathogens |
___________________________ are required for the host to reproduce | Primary symbionts |
characteristics of Secondary Symbionts | not required for reproduction, not always present in every individual, can invade different cells and live extracellularly, must provide a benefit |
what type of benefit do secondary symbionts provide for insects | nutritional benefits, protection from environment, |
what do parasitic symbionts do to infected insects | manipulate host's reproductive tissue |
white flies infected with Rickettsia | produce twice the number of offspring compared to uninfected flies |
the sperm of Wlbachia-infected male flies | can sterilize the uninfected females |
purpose of termites | decompose cellulose and hemcellulose |
termites are classified as _______________ or _______________ based on phylogeny | higher or lower |
name the three parts of the termite gut | foregut, midgut, and hind gut |
describe the posterior alimentary tract of higher termites | diverse community or anaerobes, including cellulolytic anaerobes, capable of digesting cellulose |
describe the inhabitants of the alimentary tract of the lower termites | full of anaerobic bacteria and cellulolytic protists |
Hawaiian Bobtail Squid has a mutualist relationship with | Aliivibrio fischeri |
the hawaiian Bobtail Squit harbors large populations of bioluminescent A. fischeri in | a specialized (light organ) structure; which emits light that resembles moonlight penetrating marine waters |
how does the hawaiian bobtail squid benefit from its mutualist relationship | camouflage from predators |
(not a question) the symbiotic relationship between the hawaiian bobtail squid and A. fischeri is highly specific | |
transmittion of A fischeri to hawaiian bobtain squid is | horizontal and shortly after juvenile squids hatch |
bioluminescence of hawaiian bobtail squid is controlled by | quorum sensing |
what is quorum sensing | the bacteria's ability to assess their environment for adequately numbers of them trying to carry out some collective activity |
how do the A. fischeri benefit from the squid | supplied by nutrients from squid |
hydrothermal vents support thriving communities that are fueled by ________________________ microbes | chemolithotrophic |
how do chemolithotrophs obtain energy | from chemicals and electrons from inorganic compounds |
a divers invertebrate community develops near ________________________ in the deep sea | hydrothermal vents |
where do large tube worms, clams, and mussels develop | deep-sea hydrothermal vents |
describe the mutualist (symbiotic) relationships at hydrothermal vents | chemoliithotrophic prokaryotes and vent invertebrates |
veent tube worms form endocymbiont relationships with | trophsome, which are specialized hemoglobins responsible for high blood CO2 content |
in deep sea hydrothermal vents, bacterial symbionts provide | nutrition (organic compounds) needed for host metabolism |
in deep sea hydrothermal vents, host symbionts provide | sheltered microhabitat for microbes |
what is a cold steep | an area of the ocean floor where H2S, CH4 and other hydrocarbon-rich fluid seepage occurs |
endopathogenic | insect killing |
endopathogenic nematodes | found nearly worldwide and infect a wide range of insect hosts |
Photorhabdus and Xenorhabdus | Gram-negative bacteria, brimary bacteria symbionts of entomopathic nematodes |
____________________ studies have shown an association between bacterial and nematod species is very specific | Ribosomal |
(not a question) coral skeleton very efficient light-gathering structure | |
coral skeleton harbors __________________________ symbionts including cyanobacteria, rhodophytes, chlorophytes, dinoflagellates, and diatomes | phototropic |