BIO 4302 CH 27

Check all of the following statements that apply to interspecies hydrogen transfer

- Interspecies hydrogen transfer is part of the rumen ecosystem. - Fermentation with the production of H2 and acetate in the rumen would be thermodynamically unfavorable without methanogens to quickly consume the H2. - Interspecies hydrogen transfer involves a fermentative bacterium and a methanogenic archaeon.

The microbial partners in interspecies hydrogen transfer in the rumen include fermentative bacteria and methanogens that reduce CO2 to CH4. Acetoclastic (methane made from acetate) methanogens cannot participate in interspecies hydrogen transfer. Why is this the case? Check all that apply.

- The acetate produced by the fermentative bacterium is used by the ruminant animal as a source of carbon and energy. - Methanogens that use acetate as a substrate for methanogenesis do not also use H2, and therefore would have no impact on the thermodynamics of the fermentation.

The endosymbionts of ruminant animals are useful to their hosts in which of the following ways?

- They convert glucose to organic acids. - They produce most of the vitamins needed by the ruminant. - They digest the cellulose of plant cell walls.

Analyze the statements below and choose those that are true regarding the characteristics of an amensalistic relationship.

- ants that harbor bacteria to prevent the growth of a fungus that destroys the ants' food is an example of amensalism - in an amensalistic relationship, one organism is harmed while the other is unaffected - antibiotic-producing organisms that destroy another organism is an example of amensalism

In the rumen, the carbohydrate fermentation end products include _________.

- carbon dioxide - methane - acetate

examples of predation

- organism benefits from nutrients after the host is dead - Bdellovibrio invade the cytoplasm and consume the cell contents - Vampirococcus attach to a cell surface and secrete lytic enzymes that kill the victim

examples of parasitism

- organism benefits from nutrients while the host is still alive - Chlamydophila pneumoniae reproduce inside host cells and cause a respiratory infection

In a lichen, the fungal partner _________.

- provides a substratum within which the alga grows - protects the alga from excess light intensities - provides water and minerals to the alga

In mutualism ______________.

- the mutualist is dependent on the host - the partners will not survive separately in many cases - a reciprocal benefit accrues to both partners

When Alexander Fleming discovered what was to become penicillin, he noticed that wherever mold was growing on plates of Staphylococus sp., there was a zone of inhibition of bacterial growth around the fungi. What type of symbiotic relationship does this describe?

Ammensalistic

Microorganisms in the human colon are more often being described as mutualistic with human hosts rather than commensalistic. Why has this change in the definition of a symbiotic relationship occurred?

As we learn more about the ecology of the human microbiome, we recognize our dependence on these organisms for immunity, vitamin production, and other essential processes.

________ is a predator that bores a hole through the outer membrane of its Gram-negative bacterial prey and then reproduces in the periplasm.

Bdellovibrio

How are termite-related protists and aphid-related proteobacteria similar?

Both are mutualists with their respective hosts.

Common mutualisms are seen between insects and microbes, for example, the association between aphids and ____________, which provides the host with ___________

Buchnera; amino acids

Chemolithotrophic bacteria use the electrons from sulfides to perform the ______________ that leads to carbon fixation producing nutrients for the tube worm.

Calvin cycle

Biofilm formation by Pseudomonas bacteria on the surface of a natural loofa sponge kept in the shower is an example of which type of relationship?

Commensalism

Which of the following is not a category of symbiosis?

Communalism

Patients who take antibiotics sometimes experience overgrowth of the fungus Candida albicans in their mouths and throats (a condition called thrush). C. albicans is considered part of the normal flora of the gastrointestinal tract but its population is typically limited by the presence of other microorganisms. Based on this evidence, which of the following types of symbiotic relationship do you think occurs between members of the normal flora and C. albicans

Competition

________ arises when different microbes within a population or community try to acquire the same resource.

Competition

You are studying the microbial communities in a marine estuary. You notice a layer of purple photosynthetic bacteria that use sulfide as an electron source. Sulfide is oxidized by these bacteria, which grow in a layer above sediment from which you have isolated sulfate-reducing bacteria that generate sulfide during anaerobic respiration. Based on this evidence, which of the following types of symbiotic relationships do you suspect might be occurring between these two types of bacteria?

Cooperative

A researcher proposes that the relationship between a particular bacterial species that produces a fat-soluble vitamin is mutualistic with its insect host. Which of the following procedures would best test the researcher's hypothesis?

Determine which antibiotic kills the bacteria without harming the host, then administer this antibiotic to the insect and compare its growth with and without the vitamin.

Rice seedling blight is a plant disease caused by the fungus Rhizopus microsporus that harbors intracellular bacteria in the genus Burkholderia. Interestingly, a toxin produced by the Burkholderia bacteria kills the seeds; the fungus then consumes the poisoned seeds. In the laboratory R. microsporus and the Burkholderia bacteria can be grown in pure culture. Which of the following pairs of words best describe this microbial symbiosis?

Endosymbiont; Cooperation

You have isolated a soil protozoan, which you are now trying to grow in pure culture. You have tried many different types of media but find you can only grow the protozoan if bacteria are also present in the medium. You note that the bacterial population declines as the protozoan population increases. Based on this evidence, which of the following types of symbiotic relationships do you suspect might be occurring between the protozoan and the bacteria?

Predatation

The relationship between the bacterium Xenorhabdus nematophila and its nematode host, Steinernema carpocapsae, is classified as cooperation because both organisms benefit and _________.

X. nematophila and S. carpocapsae can be grown separately

gnotobiotic

animals that are free of microorganisms

Pseudonocardia is an organism that is hosted by _________.

ants that cultivate fungal gardens

Mutualism is found in termites where protists ferment ___________, releasing carbon dioxide and hydrogen that are then converted to _________ by bacterial symbionts.

cellulose; acetate

The relationship between the tube worms Riftia and sulfide-oxidizing _______________ bacteria is mutualistic.

chemolithotrophic

The bacteria are _______________, they use _________ as an electron donor and oxygen as the terminal electron acceptor. The worms have specialized _________________ that carries H₂S and O₂ to the endosymbionts, which are contained in a specialized organ called the _____________

chemolithotrophs; sulfide ; hemoglobin; trophosome

When Nitrobacter utilizes nitrite produced from ammonia by Nitrosomonas to obtain energy by converting the nitrite to nitrate, the relationship between the two organisms is _________.

commensal

Because you have always been fascinated by spiders and bacteria, you decide to study the microbiome of a species of spider that is locally abundant. You are able to cultivate many bacteria from the spiders gut in the lab, and the spiders do not appear to be negatively affected by treatment with antibiotics that you know will inhibit the growth of these bacteria. Based on this evidence, which of the following types of symbiotic relationships do you suspect might be occurring between the spider and the bacteria?

commensalistic

In the rumen, food is quickly attacked by cellulase _________.

enzymes produced by microbes

pathogen

infectious agent that causes disease

Methanogens are always engaged in relationships with other microbes because methane production requires _________.

interspecies hydrogen transfer

In peat bogs, ________________ bacteria live in sphagnum stems and oxidize methane to produce carbon dioxide that the plant can fix.

methanotrophic

he energy yield from the bacterial respiratory pathway is used to fix CO₂, which is obtained either from the Riftia hemoglobin, freely from the bloodstream, or in the form of _________________. The organic carbon is synthesized using the same mechanism as plants and algae, that is via the __________________ cycle, albeit far from any sunlight.

organic acids; Calvin-Benson

Riftia spp. are tube worms that live in communities on the ocean floor near hydrothermal vents. They lack a mouth and gut and rely on endosymbiotic bacteria to provide them with __________________. This mutualism is so beneficial, the worms can grow to over a meter long.

organic carbon

symbiosis

physical association of two or more different organisms

Which of the following processes is not one that is common to all symbionts?

predation

Microbes convert cellulose to organic acids such as acetate in the ___________________

rumen ecosystem

Any microorganism that spends a portion of its life associated with another organism of a different species is engaged in _________.

symbiosis

ectosymbiont

symbiotic relationship between an organism and another that lives on its surface

endosymbiont

symbiotic relationship between an organism and another that lives within it

The reason coral reefs are among the most productive and successful ecosystems is due to _________.

the coral-dinoflagellate mutualistic relationship

Recent metagenomic investigations reveal that human microbial flora is extremely diverse and is best described as _________.

vital to our survival

coevolution

when two organisms evolve together

Dinoflagellates that exist endosymbiotically within a variety of marine invertebrates are called _________.

zooxanthellae

Reef-building coral harbor _____________, members of the dinoflagellates that provide ___________________ in exchange for nitrogenous compounds and other nutrients.

zooxanthellae; fixed carbon

Several cases of an emerging infectious disease are reported in workers at a research station that borders a tropical rainforest region. The pathogen is identified as a species of bacteria carried by nematodes that infect mosquitos, and disease transmission occurs in a human host following a mosquito bite. Which organisms should be targeted in the treatment of infected patients?

Nematode and bacteria