Exam 2

Phylogenetic analysis of organisms across the three domains of the tree of life indicate that:

Archaea are more closely related to Eukarya than they are to bacteria

In Lenski's long-term experiment on evolution in E. coli, the bacteria use glucose as a carbon source and an electron donor, and oxygen as an electron acceptor. There are other nutrients and minerals added to the media, including citrate. After about 30,000 generations of the experiment, a sub-population of E. coli emerged that could grow using citrate, instead of glucose. Which evolutionary processes caused this novel trait to occur?

Mutation

The genus Rhodospirillum belongs to the ____ proteobacteria that can carry out ____ in the absence of organic matter and oxygen, if light is abundant.

Alpha/photoautotrophy

While looking under the microscope at a sample of red snow from the colorado rockies you notice some motile cells that contain mitochondria, have a single flagellum, but do not contain chloroplasts. You also notice some of these motile cells emerging from sporangia attached to cells of a Chlamydomonas snow alga and from pollen grains in the snow. These motile cells are most likely ____ in the phylum ____.

Fungi / Chytridiomycota

The spirochetes are a large group of very diverse bacteria that inhabit many environments ranging from anaerobic sediments tot he bodies of most animals. Which of the following statements about spirochetes is true?

Mutualistic spirochetes, such as those that live in termite guts, fix nitrogen because they live in a nitrogen-poor environment.

In Lenski's long-term experiment on evolution in E. coli, the bacteria use glucose as a carbon source and an electron donor, and oxygen as an electron acceptor. There are other nutrients and minerals added to the media, including citrate. After about 30,000 generations of the experiment, a sub-population of E. coli emerged that could grow using citrate, instead of glucose. The mutant sub-population of E. coli that utilizes citrate instead of glucose co-exists with the original population that uses glucose. What process would explain the coexistence of the two strains?

Niche partitioning - the sub-populations are using different resources.

A recent research study compared competition in two different types of soils. Soil 1 had high microbial abundances and diversity, but the microbes present in the soil usually used the same types of metabolic pathways. In soil 2, there were lower cell densities, lower levels of metabolic overlap, and the microbes within the soil aggregates were spatially structured/separated based on species and metabolism. In which soil would you most expect to find the highest levels of antibiotic production?

Soil 1

During the conversion of milk to yogurt, a variety of non-spore forming firmicutes grow rapidly in the milk by fermenting the sugar lactose to lactic acid. The initial phase of this is carried out by bacteria in the genus ____. After lactic acid builds up to a certain level, acid tolerant members of the genus ____ take over and complete the conversion of lactose to lactic acid, resulting in the coagulation of the proteins in the milk.

Streptococcus / Lactobacillus

You isolate a filamentous organism from soil that does not contain chloroplasts or mitochondria and forms greenish-blue colonies with conidia spores when it is entering the stationary phase of its growth cycle. Further work with this organism reveals that is produces a potent antibiotic and has DNA GC content of 75%. To what genus does it most likely belong?

Streptomyces

Adenoviruses are common viruses that cause a range of illness. Many adenoviruses require access to host cell DNA yet lack the transport mechanisms to ge their viral nucleic acids and enzymes into the nucleus. Which of the following would be an expected observation of adenoviral infectivity and replication?

The inability to infect non-growing cells

In many aquatic sediments that are regularly exposed to sunlight, layers of different types of photosynthetic bacteria grow and come together as a multi-layered microbial mat. The top layer of these mats is usually composed of cyanobacteria that show phototaxis towards ____ light. Underneath the top layer there are often red or purple layers of bacteria that contain organisms such as rhodospirillum that are photophobic to ____ light.

Visible/visible

In general, soil microbial communities have ____ microbial abundances and ____ microbial diversity compared to marine and freshwater environments.

higher/higher

Truffles are hypogeous fungal fruiting bodies that are eaten by many animals, including humans. Why do you think they taste and smell so good to many animals, including humans? One plausible explanation is that they have co-evolved with animals and produce pleasant odors and tastes that attract animals...

that then disseminate their sexual spores (ascospores)

T/F: photosynthesis and its products "drive" the microbial food webs in both marine and soil environments

true

Wild Type Pigment Mutant Graph thing -- What would explain the increase in the relative abundance of the mutant strain compared to the wild type strain under dark conditions, but not light conditions?

-Competition for resources -Natural selection

Which processes would account for the high level of genetic diversity found within the Salmonella enterica species?

-Horizontal gene transfer -High rates of mutation -Differences in selective pressures between environments in which the bacterium lives

Many microbial eukaryotes have both sexual and asexual life cycles. Which of the following statements regarding the life cycle of a mushroom-forming fungus in the basidiomycota is correct?

-Hyphae of opposite matching types fuse forming dikaryotic (n+n) hyphae with two nuclei in each cell. -Basidiospores are haploid (1n) and germinate to form haploid hyphae -Meiosis occurs in structures called basidia, resulting in the formation of four basidiospores per basidium.

What role do viruses play in microbially-facilitated nutrient cycling in the ocean?

-Viruses infect phytoplankton, which releases dissolved organic matter (DOM) for heterotrophic bacteria to consume -Viruses infect heterotrophic bacteria, which releases inorganic nutrients and carbon into the ocean for other microbes to use, and for long-term storage.

Place the following events in the evolution of microbial life on early earth in order by matching the numbers:

1: RNA based life 2: First microbial cells with double stranded DNA genomes 3: Anoxygenic photosynthesis 4: Oxygenic photosynthesis 5: Bacterial aerobic heterotrophic respiration 6: Endosymbiosis of aerobic bacteria, which evolved into mitochondria 7: First microbial eukaryotic cells

Why does the production of conidia occur first in the middle of a fungal colony and not at the edges?

Middle cells are older, and are running out of food

Spike proteins on SARS-CoV-2, the virus that causes covi-19 disease, bind to receptors on human cells, helping the virus to enter. A spike protein is made up of three smaller peptides in open or closed orientations; when more are open, its easier for the protein to bind to human cells. A newly described mutation - the result of a single letter change to the viral RNA code - seems to relax the connections between peptides. This mutation makes open conformations more likely. How might this mutation affect the inefectivity of the virus compared to strains with closed orientations?

Increase the likelihood of infection

Members of which of the following genera of the gammaproteobacteria can use cooperative swarming behavior to move up the human urethra and through catheters?

Proteus

What does not accurately describe the differences in microbial and viral abundances, and viral infection, between riverine and marine environments?

Riverine environments have higher rates of viral infection, due to higher infection efficiencies, than marine environments

Match the environment to the corresponding selective pressure that is unique to microbes in that environment: -Soil -Marine -Freshwater

Soil -- high microbial density Marine -- high salinity Freshwater -- seasonal variability

A recent research study compared competition in two different types of soils. Soil 1 had high microbial abundances and diversity, but the microbes present in the soil usually used the same types of metabolic pathways. In soil 2, there were lower cell densities, lower levels of metabolic overlap, and the microbes within the soil aggregates were spatially structured/separated based on species and metabolism. In which soil would you expect to find higher levels of competition?

Soil 1

The great plate count anomaly describes which of the following phenomena?

The majority of heterotrophic bacteria (99%) from lower nutrient environments have not been grown in culture

Which of the following characteristics is unique to fungi and not found in bacteria?

The presence of ergosterol in cell membranes

Phylogenetic trees that show evolutionary relationships between microorganisms are constructed using which of the following methods?

The quantitative comparison of the DNA sequences of "marker"genes, such as the small sub unit of the ribosomal RNA gene

Which is the most accurate statement in terms of how environmental changes, such as those associated with global climate change, are likely to affect competition interactions between microorganisms?

The way in which environmental change affects microbial competition is context dependent - it depends on the specific effects of the environmental change on the ecosystem.

The influenza A virus genome is composed of eight negative-sense RNA segments, all of which must be packaged to produce an infectious virion. Major changes in the genome of the influenza virus result from packaging of ____ from strains of the virus from different animals. These packaging errors result in ____ and usually occur in ____.

Viral genome segments / antigenic shifts / pigs

You discover a large chloroplast - containing microbe that has two flagella and a nucleomorph in addition to a true nucleus. Based on these traits, this organism is likely to be a ____, that gained its ability to photosynthesize as a result of a ____ endosymbiont event.

eukaryote / secondary

While hiking near tree line in the colorado rockies you notice a group of bright red mushrooms with white specks on their caps growing near some sub alpine fir trees. These mushrooms are probably in the genus Amanita and are the ____ fruiting stage of an ____ association with the roots of the nearby trees. This type of mutualistic relationship protects plant roots from pathogens and ____ the absorptive surface area of the root system which results in increased nutrient uptake for the plant.

sexual / ectomycorrhizal / increases