Chapter 18

Outer membrane (sheath)

A

Bacteria used in wastewater treatment include those that can convert ammonia and nitrite to nitrate, decreasing the reduced nitrogen content of the sewage. These bacteria, such as Nitrosomonas spp., often belong in Choose one: A. Betaproteobacteria. B. Alphaproteobacteria. C. Gammaproteobacteria. D. Deltaproteobacteria.

A. Betaproteobacteria. Nitrosomonas spp. are Betaproteobacteria.

Which bacterial taxon includes members that stain positive for the acid-fast stain? Choose one: A. Nitrospirales B. Actinomycetes C. Cyanobacteria D. Bacteroidetes

B. Actinomycetes The acid fast stain tests positive for actinomycetes that contain mycolic acids in their cell wall.

Some, but not all, cyanobacteria produce differentiated cell types known as Choose one: A. thylakoids. B. heterocysts. C. carboxysomes. D. gas vesicles.

B. heterocysts. All cyanobacteria fix carbon. Many also fix nitrogen, but not all of these form heterocysts.

The two major genera of Gram-positive bacteria include the _______________ , which contains the endospore-forming genera (e.g., Bacillus and Clostridium), and the _______________, which contains some filamentous forms (e.g., Streptomyces) that produce exospores. Choose one: A. high GC Actinobacteria ; low GC Firmicutes B. low GC Firmicutes ; high GC Actinobacteria C. high GC Firmicutes ; low GC Actinobacteria D. low GC Actinobacteria ; high GC Firmicutes

B. low GC Firmicutes ; high GC Actinobacteria The two major phyla of Gram-positive bacteria are distinguished primarily on the basis of their GC genomic content. Evidence from sequencing data suggests that endospore-formation was an ancestral trait of Firmicutes that was subsequently lost during evolution of such genera as Lactobacillus, Streptococcus, Staphylococcus, etc. Similarly, only some groups within the Actinobacteria, (including the largest genus, Streptomyces) produce exospores on aerial mycelia.

Periplasmic space

B

Which of the following is a pathogenic organism that lacks cell walls and forms elementary bodies when outside a host? Choose one: A. Chlamydia B. Mycoplasma C. Planctomycetes D. Verrucomicrobium

A. Chlamydia, a common sexually transmitted disease, lacks cell walls and forms elementary bodies that are a type of endospore. Mycoplasma and planctomycetes do not form elementary bodies. Verrucomicrobium have cell walls.

Which of the following statements regarding Thermotoga maritima is true? Choose one: A. The cells have a loosely bound sheath, or "toga." B. Its genome appears not related to archaea. C. It is a mesophile. D. It is an oxygen-reducing respirer.

A. The cells have a loosely bound sheath, or "toga." Thermotogae is a thermophile and sulfur-reducing respire. The cells have a loosely bound sheath, or "toga." Nearly a quarter of the T. maritima genome appears to derive from archaea.

Which of the following is true of rhizobia? Choose one: A. They can colonize specific plant hosts and fix nitrogen. B. They are in the same phylum as the plant-associated, nitrogen-fixing Frankia. C. They can be free living in the soil or colonize any plant species. D. They cannot survive outside of a host plant cell.

A. They can colonize specific plant hosts and fix nitrogen. Rhizobia form highly specific mutualistic associations with plants in which the bacteria fix nitrogen for the plants. Rhizobia can also be free living and are in a different phylum from the Gram-positive actinobacteria Frankia.

The bacterium Listeria monocytogenes enters a new host by: Choose one: A. ingestion of contaminated food. B. tick bites. C. inhalation of droplets. D. puncture wounds. E. sexual contact.

A. ingestion of contaminated food. Listeria is a difficult pathogen to control because (as a psychrotroph) it grows well at refrigeration temperatures. It is most commonly identified as a contaminant in foods such as soft cheeses, sauerkraut, and even ice cream!

Which of the following is in the correct sequence for a typical Chlamydia life cycle? Choose one: A. Transmission outside host cells as an elementary body, endocytosis of the elementary body, transformation into a reticulate body to reproduce, transformation into elementary bodies to be released B. Transmission outside host cells as an elementary body, endocytosis of the elementary body, transformation into a reticulate body to reproduce, release of reticulate bodies, transformation into elementary bodies C. Transmission outside host cells as a reticulate body, endocytosis of the reticulate body, transformation into an elementary body to reproduce, transformation into reticulate bodies to be released D. Transmission outside host cells as an elementary body, transformation into a reticulate body, endocytosis of the reticulate body, transformation into elementary bodies to be released

A. Transmission outside host cells as an elementary body, endocytosis of the elementary body, transformation into a reticulate body to reproduce, transformation into elementary bodies to be released Elementary bodies cannot reproduce but reticulate bodies are incapable of infection outside a cell and are vulnerable to osmotic shock.

A bacterial phylum is generally defined based on: Choose one: A. ancestry and key traits. B. genetic relatedness only. C. key traits regardless of ancestry. D. morphology and shared habitats. E. shared habitats and common ancestor.

A. ancestry and key traits. Phylogenetic analyses provide the framework by which bacterial phyla are defined. But because all life is descended from a common ancestor (or ancestral community), scientists also use key traits when creating phyletic divisions. In practice then, a bacterial phylum is a group of organisms sharing a common ancestor that diverged early in the evolution of the domain that also shares key traits. Individual species within a phylum may still exhibit remarkable diversity with respect to aspects of metabolism and habitat.

Deep-branching Gram-negative phyla are considered distinct from the Proteobacteria because they Choose one: A. branch more deeply than the five Proteobacterial groups. B. have only one metabolic pathway in common, unlike the Proteobacteria. C. lack the outer membrane that all Proteobacteria have. D. are all obligae aerobes.

A. branch more deeply than the five Proteobacterial groups. Comparisons of the 16S rRNA sequences show the deep-branching Gram-negative phyla diverging earlier and more from the Proteobacteria than the different groups of the Proteobacteria from each other.

Cyanobacteria contain carboxysomes. Carboxysomes are involved in Choose one: A. carbon dioxide fixation. B. cell buoyancy in aquatic habitats. C. providing rigidity to the cell D. nitrogen fixation of inorganic N2 into ammonia.

A. carbon dioxide fixation. Carboxysomes are organelles for carbon dioxide fixation.

Species in the Bacillus genus Choose one: A. contain members that are extremophiles. B. contain members that are photosynthetic. C. may have a spiral shape. D. are members of the Proteobacteria phylum.

A. contain members that are extremophiles. Bacilli are rods. Many members, such as B. halodurans, with its high salt affinity, are extremophiles. Proteobacteria are Gram-negative, whereas the bacilli are Gram-positive.

Cyanobacteria are important ecologically because they Choose one: A. fix carbon producing oxygen as a byproduct; many also fix nitrogen. B. decompose living tissue. C. are important pathogens allowing nutrient cycling. D. can use toxic byproducts of other microbes as metabolic substrates.

A. fix carbon producing oxygen as a byproduct; many also fix nitrogen. Cyanobacteria are important primary producers because they perfrom oxygenic photosynthesis and many also fix nitrogen. This makes them foundational to many ecological systems.

A mutant strain of Listeria that failed to polymerize actin would be less able to Choose one: A. invade neighboring cells. B. survive in the cytoplasm. C. direct host cell motility. D. multiply in the cytoplasm. E. detoxify digestive enzymes.

A. invade neighboring cells. Once it is free in the host cytoplasm, Listeria nucleates host cell actin at one pole of the bacterial cell. The resulting filaments move the bacterium through the cytoplasm. Membrane protrusions form as the bacteria are pushed through the host plasma membrane to be taken up by neighboring cells.

Cyanobacteria is the name of a particular bacterial Choose one A. phylum. B. genus. C. species. D. order.

A. phylum. Cyanobacteria refers to a phylum.

Experimental mice reared in the absence of segmented filamentous bacteria (SFB) would likely be: Choose one: A. prone to infectious disease. B. infertile. C. unable to heal properly. D. overweight. E. depressed and/or anxious.

A. prone to infectious disease. The SFB known as "Candidatus Savagella" specifically attaches to cells in the lymphoid tissue of the small intestine (Peyer's patches) to induce proper development and activation of the immune response. Mice colonized by these bacteria show enhanced resistance to infection by the pathogen Citrobacter rodentium compared to mice which lack these symbionts.

Botox is a medical application using the toxin produced by Clostridium botulinum to Choose one: A. relax muscle spasms. B. prevent recurrent infections. C. kill pathogenic microbes in the gut. D. kill pathogenic microbes in the central nervous system.

A. relax muscle spasms. The toxin produced by C. botulinum is a paralytic agent, so it can be used to relax muscle spasms and reduce the appearance of wrinkles.

Planctomyces are similar to eukaryotic cells in that Choose one: A. their DNA is surrounded by a double membrane. B. they are capable of nitrogen fixation. C. they undergo sexual reproduction. D. they contain mitochondria.

A. their DNA is surrounded by a double membrane. Planctomyces are bacteria with a "nuclear membrane."

Why do the pathogens Rickettsia rickettsii and Listeria monocytogenes resemble each other? Choose one or more: A. their ability to move directly between host cells B. their ability to live independently of a host C. their mode of entry into new host organisms D. their ability to polymerize host actin E. their Gram reaction F. their ability to live intracellularly

A. their ability to move directly between host cells D. their ability to polymerize host actin F. their ability to live intracellularly Both species are intracellular pathogens that can polymerize host cell actin. The actin tails provide motility within the cytoplasm and facilitate infection of neighboring cells. The similarities end there. Rickettsia rickettsii is an alphaproteobacteria (and thus Gram-negative) and obligate endosymbionts that share a common ancestry with mitochondria. Rickettsia rickettsii is the etiological agent of the serious tick-borne disease Rocky Mountain spotted fever. Listeria monocytogenes (which causes listeriosis) is a Gram-positive species within the Firmicutes phylum. These bacteria can exist as free-living members of soil and water communities and cause disease when they are ingested in contaminated foods.

The most deep-branching bacterial phyla that diverged earliest contain many members that are Choose one: A. thermophiles. B. pathogenic. C. oxygenic photoautotrophs. D. lacking a cell wall.

A. thermophiles. The most deeply branching bacterial phyla (i.e., those that appear to have diverged earliest) include thermophiles and hyperthermophiles.

Lithotrophic organisms Choose one: A. use an inorganic compound as an electron donor. B. by necessity are also phototrophic. C. are restricted to Proteobacteria. D. are restricted to areas with organic matter available.

A. use an inorganic compound as an electron donor. A lithotroph gains energy by oxidizing inorganic compounds. Lithotrophs are found in several different phyla and need not be phototrophic.

Members of the Actinobacteria often have unique patterns of cellular growth. Which of the following genera includes species that grow as irregularly shaped branched rods (as shown here) but are coccoid shaped when nutrient limited? Choose one: A. Mycobacterium B. Arthrobacter C. Streptomyces D. Corynebacterium

B. Arthrobacter Arthrobacter spp. are common inhabitants of soils. The branching forms observed during active growth probably function to increase the amount of surface area available for nutrient uptake in soils (similar to fungal mycelia). Many species break down environmental pollutants including herbicides and pesticides, and thus are being investigated for use in bioremediation strategies.

Which phototrophic bacteria are obligate anaerobes containing chlorosomes that deposit sulfur extracellularly? Choose one: A. Chloroflexi B. Chlorobi C. Firmicutes D. Cyanobacteria

B. Chlorobi Chlorobi are a phylum of Gram-negative bacteria. They are obligate anaerobes, "green sulfur" phototrophs that photolyze sulfides. Chloroflexi and cyanobacteria are not obligate anaerobes. Firmicutes do not have chlorosomes.

Bacteria in which taxon are extremely resistant to radiation? Choose one: A. Aquificales B. Deinococcus C. Firmicutes D. Chloroflexi

B. Deinococcus Deinococcus bacteria can be radiation resistant.

A Gram-positive bacterium with a low GC content may be a(n) Choose one: A. Nitrospirae. B. Firmicute. C. Proteobacteria. D. Actinobacteria.

B. Firmicute. Firmicutes are a phylum of low GC content Gram-positive bacteria. Proteobacteria and Nitrospirae are Gram-negative and Actinobacteria have a high GC content.

What microbe of the Epsilonproteobacteria was made famous by researchers drinking it to demonstrate that it can cause gastric ulcers? Choose one: A. Escherichia coli B. Helicobacter pylori C. Mycobacterium leprae D. Salmonella enterica

B. Helicobacter pylori Barry Marshall drank a culture of H. pylori to demonstrate it can cause stomach ulcers, an act that eventually earned him and his colleague J. R. Warren a Nobel Prize.

Once inside the host, how does Listeria evade phagocyte-mediated killing? Choose one: A. It has evolved resistance to host digestive enzymes. B. It uses a toxin to escape the phagosome. C. It produces a capsule which makes the cells difficult to phagocytose. D. It produces toxins that lyse host cells. E. It prevents fusion of a phagosome with a lysosome.

B. It uses a toxin to escape the phagosome. During an initial infection, phagocytes engulf Listeria cells. This process encloses the bacterium within a membrane vacuole known as a phagosome. Normally, a phagosome fuses with a lysosome (a membrane vesicle containing digestive and toxic enzymes) to produce a phagolysosome. But before this can happen, Listeria creates holes in the phagosome and escapes into the cytoplasm where it can safely replicate. Curiously, the bacterium's pore-forming toxin (listeriolysin O) is specifically activated by the low pH within the phagosome.

Some of the most ecologically important microbes include _________, which are nitrogen-fixing endosymbionts of plants. Choose one: A. Agrobacterium tumifaciens B. Rhizobium spp. C. Nitrosomonas spp. D. Rickettsia rickettsii

B. Rhizobium spp. While Rickettsia and Agrobacteria are endosymbiotic, they are not nitrogen fixers like Rhizobium. Nitrosomonas is a nitrifier and not endosymbiotic.

Which of the following emerging phyla includes species that may be beneficial inhabitants of mammalian gastrointestinal tract? Choose one: A. Spirochetes B. Verrucomicrobia C. Chlamydiae D. Planctomycetes E. Fusobacteria

B. Verrucomicrobia The Verrucomicrobia are becoming recognized as a very widely distributed and important group of bacteria. However, few have been cultured, and their 16S rDNA genes are so divergent from other bacteria that they have largely gone undetected in metagenomics surveys using "universal" bacterial PCR primers. Known habitats include soils, oceans, freshwater, and the human gut microbiome.

Which of the following represent mechanisms by which Proteobacteria generate a proton motive force for ATP synthesis? Choose one or more: A. reduction of CO2 by H2 B. aerobic oxidation of H2S C. anaerobic oxidation of glucose D. photolysis of H2O E. light-driven proton pumps

B. aerobic oxidation of H2S C. anaerobic oxidation of glucose E. light-driven proton pumps Proteobacteria are capable of a wide variety of energy yielding reactions. Indeed, many types of reduced organic or inorganic molecules can be used for growth by proteobacterial organotrophs or lithotrophs, respectively. (Some even switch between these modes of growth). The electrons from oxidized substrates enter the electron transport chain and a proton motive force (which drives subsequent ATP synthesis) is generated as they are passed to a terminal electron acceptor. Again, a variety of molecules may be used as terminal oxidants. In the case of aerobic respiration, it is oxygen, while alternative oxidants (e.g., nitrate, ferric iron) are used by organisms respiring anaerobically. A few proteobacteria are true autotrophs, while others supplement heterotrophy with phototrophy. Some even use light-driven proton pumps (analogous to archaeal bacteriorhodopsin) to establish a proton motive force for ATP synthesis. No proteobacteria, however, split water during photosynthesis. That process generates oxygen and is restricted to cyanobacteria lineage (which includes chloroplasts). Oxidation of H2 coupled to reduction of CO2 generates methane. This mode of anaerobic respiration is restricted to some members of Archaea.

The lactic acid bacteria Choose one: A. are major food contaminants. B. are important in the food industry. C. are used to produce industrial solvents. D. can be used in bioremediation.

B. are important in the food industry. The lactic acid bacteria of firmicutes are used heavily in the food industry for their fermentation pathway products. Other firmicutes can be used for these other applications.

All Proteobacteria share Choose one: A. the same host preference. B. the same cell envelope structure. C. the same cell morphology as all are cocci. D. a common metabolic strategy for energy production.

B. the same cell envelope structure. All the Proteobacteria share a similar cell envelope structure and are Gram-negative. Their cell morphologies and metabolisms vary widely. Not all have hosts, and in those that do, the hosts vary.

Protoplasmic cylinder

C

Which of the following is NOT a deep-branching Gram-negative phylum? Choose one: A. Fusobacteria B. Acidobacteria C. Actinobacteria D. Chlorobi

C. Actinobacteria Actinobacteria are Gram-positive microbes. All the rest are deep-branching Gram-negative phyla.

The closest relatives of mitochondria are found in which bacteria class? Choose one: A. Betaproteobacteria B. Gammaproteobacteria C. Alphaproteobacteria D. Deltaproteobacteria

C. Alphaproteobacteria Mitochondria are most closely related to Alphaproteobacteria, specifically Rickettsia.

The cyanobacteria are thought to have given rise to which eukaryotic organelle? Choose one: A. Mitochondria B. The nucleus C. Chloroplasts D. Lysosomes

C. Chloroplasts The photosynthetic, chlorophyll-containing cyanobacteria gave rise to chloroplasts.

Which of the following qualities of an organism signifies that it is considered an "emerging organism"? Choose one: A. It is responsible for new disease outbreaks. B. It has evolved resistance to previously effective antibiotics. C. It belongs to a novel clade only recently known to science. D. It is undescribed, and there is no formal evidence of its existence. E. It cannot be amplified using so-called "universal primers."

C. It belongs to a novel clade only recently known to science. The term "emerging" has more than one meaning to a microbiologist. In this context, it refers to newly discovered clades, usually known only by sequence data. In some cases, these organisms are so unlike cultured species that their 16S rRNA genes cannot be amplified by standard "universal" primers. Microbes associated with an increased prevalence of disease are referred to as "emerging pathogens," while other pathogens "re-emerge" by acquiring resistance to previously effective therapeutants.

Which of the deep-branching Gram-negative phyla contains primarily chemolithotrophs? Choose one: A. Bacteroidetes B. Acidobacteria C. Nitrospirae D. Chlorobi E. Fusobacteria

C. Nitrospirae The phylum Nitrospirae contains only one order, one class, and one family. There are currently three genera with this phylum that have been validated. Most Nitrospira oxidize nitrite for growth (they are nitrifiers), but iron-oxidizing species (e.g., in the genus Leptospirillum) have also been described. These bacteria are autotrophic and contain carboxysomes for carbon fixation.

Imagine that you have isolated what appears to be a new species of thermophile from a microbial mat at Yellowstone National Park. This organism can grow up to 90ºC and contains ether-linked lipids in its plasma membrane. Using whole-genome sequence data, your team pieces together a single circular chromosome—about half the size of the one in E. coli. About 54% of its genes have functional assignments, but there is an interesting pattern in their biological roles. Specifically, genes required for transcription and translation are most like bacterial orthologues, while genes encoding nutrient transporters and electron transport proteins are most similar to thermophilic archaea. What is the best interpretation of your data? Choose one: A. You have isolated a type of primitive thermophilic eukaryote. B. This is an evolving endosymbiosis between an archaeal host and internalized bacterium. C. This is a bacterium which has acquired a surprisingly large number of archaeal genes. D. The cultures you made of this organism contain codependent bacteria and archaea. E. This is an archaeon which has taken up large segments of bacterial DNA.

C. This is a bacterium which has acquired a surprisingly large number of archaeal genes. Because essential housekeeping genes (e.g., those involved in gene expression) are more likely to be inherited vertically, this organism can be assumed to be a bacterium which acquired the archaeal genes via extensive horizontal gene transfer. In fact, this bacterium would likely represent a new species of Aquifex or Thermotoga. These genera are deeply-branching bacterial thermophiles with many similarities to the archaea which share their habitats, including ether-linked lipids in Aquifex membranes. If this organism descended from the archaeal lineage, its transcription and translation machinery would more closely resemble eukaryotes (to which archaea are more closely related). That would also be the case if this new organism was an archaeon with a bacterial endosymbiont (which is how eukaryotes are believed to have evolved). No eukaryotes are known that are capable of growth at 85°C, and the possibility that this is a mixed culture is highly unlikely because sequence analysis revealed the presence of a single circular chromosome.

Verrucomicrobia contain cytoskeletal elements whose genes were likely acquired by transfer from what? Choose one: A. archaea B. mycobacteria C. eukaryotes D. chlamydia E. spirochetes

C. eukaryotes In 2002, tubulin genes were identified in the Verrucomicrobium genus Prosthecobacter. These were shown to be functional, true tubulins and based on high-sequence identity, appear to have been acquired by horizontal gene transfer from eukaryotes. Further, when the Prosthecobacter genes were expressed in E. coli, microtubules were observed which ran the entire length of the cell. Some ciliates are even known to harbor episymbiont verrucomicrobia whose harpoon-like tubulins function as a type of defense for their host!

Bacterial cells can be distinguished from cells in the other two domains because only bacterial cells Choose one: A. lack a nucleus. B. contain chloroplasts. C. have peptidoglycan cell walls. D. can be pathogenic to humans.

C. have peptidoglycan cell walls. Cells in all three domains may have cell walls, but peptidoglycan is unique to bacterial cell walls.

Spirochete flagella Choose one: A. are considerably shorter than typical bacterial flagella. B. are not used for motility as they are internal, but rather are for avoiding phagocytosis. C. rotate like other bacterial flagella, but are internal so cause the cell to corkscrew. D. whip in a manner similar to eukaryotic flagella.

C. rotate like other bacterial flagella, but are internal so cause the cell to corkscrew. The spirochete flagella uses a proton-driven motor to rotate, but being internalized causes the whole cell to corkscrew.

Flagellum

D

Which taxon includes bacteria that parasitize other bacteria? Choose one: A. Rickettsia B. Salmonella C. Phages D. Bdellovibrios

D. Bdellovibrios Bdellovibrio species, of the Deltaproteobacteria, can attack proteobacterial host cells. Salmonella do not parasitize other bacteria. Rickettsia infect eukaryotic cells and phages are viruses.

Which of the following clades contains Gram-positive, endospore-forming phototrophs? Choose one: A. Cyanobacteria B. Chlorobi C. Chloroflexi D. Firmicutes

D. Firmicutes The only endospore-forming phototrophs listed are Firmicutes.

Which of the following is NOT a major bacterial phylum? Choose one: A. Verrucamicrobia B. Chlamydiae C. Proteobacteria D. Platyhelminthes

D. Platyhelminthes are flatworm animals.

Which bacterial phylum has periplasmic flagella? Choose one: A. Bacteroides B. Chloroflexi C. Nitrospirae D. Spirochetes

D. Spirochetes Spirochetes are a phylum of bacteria with a unique morphology—a flexible, extended spiral that twists due to periplasmic flagella.

The members of a bacterial phylum share Choose one: A. a common metabolic strategy. B. a common morphology. C. the same habitat. D. a common ancestor.

D. a common ancestor. Cells in a phylum all have a common ancestor, but they may have distinct morphologies, distinct metabolic strategies, and may live in distinct habitats.

The only bacteria that produce oxygen gas are Choose one: A. chlorobi. B. chloroflexi. C. clostridia. D. cyanobacteria.

D. cyanobacteria. Cyanobacteria are the only oxygenic prokaryotes.

Imagine that you are an early microbiologist attempting to reproduce Louis Pasteur's famous experiments which helped disprove spontaneous generation. You first prepare a hay infusion (a type of nutrient broth), then boil it for 20 minutes in a swan-necked flask of the same design that Pasteur used. Upon cooling and incubation at room temperature, you notice that your broth has become cloudy (turbid) only a few days later. What did your broth contain that Pasteur's likely did not? Choose one: A. hyperthermophilic archaea B. sufficient oxygen C. myxospores D. endospores E. sufficient nutrients F. akinetes

D. endospores Pasteur's experiments were considered near conclusive proof against the theory of spontaneous generation. Pasteur boiled a nutrient broth that was designed (via the swan-neck) to permit gas exchange while at the same time preventing particles (dust, airborne organisms, etc.) from falling into the liquid. John Tyndall was initially unsuccessful in repeating these experiments because his hay infusions contained Bacillus endospores from the soil. These survived the initial heat treatment, and germinated into actively growing (vegetative cells) after the medium cooled. Because vegetative cells are not heat resistant, repeated cycles of boiling followed by cooling will eventually sterilize even media containing endospores.

Imagine that you are examining a culture of Anabaena and observe clusters of bacteria surrounding the larger differentiated cells that occur at regular intervals along the filaments. These bacteria are probably: Choose one: A. pathogenic and causing the nearby cells to lyse. B. nodulating nitrogen-fixing bacteria. C. harvesting light wavelengths not absorbed by the cyanobacteria. D. growing on organic compounds leaked from the cyanobacterium. E. acting as antennae to funnel photons to cyanobacterial photosystems.

D. growing on organic compounds leaked from the cyanobacterium. Studies have shown that nitrogen-fixation rates are enhanced in cultures of Anabaena containing heterotrophic bacteria. These "symbionts" are observed localized around the cyanobacterial heterocysts where they grow aerobically on photosynthetic exudate provided by Anabaena. Such activity helps protect the notoriously O2-sensitive nitrogenase enzyme in heterocysts.

Penicillin antibiotics would be ineffective against mycoplasma because mycoplasma Choose one: A. lack ribosomes. B. acquire many amino acids from the host. C. are not phylogenetically bacteria. D. lack cell walls.

D. lack cell walls. Penicillin inhibits cell wall formation.

Actinomycetes are important in medicine because of all but their Choose one: A. ability to produce antibiotic compounds. B. symbiotic relationships with other organisms. C. importance as pathogens. D. use in the food industry.

D. use in the food industry. Actinomycetes include many antibiotic producers, the pathogens causing tuberculosis, leprosy, and diphtheria among others, and form symbioses with plants and animals.

Which Gram-negative phylum contains the most metabolic diversity of any phylum and the largest number of described species? Choose one: A. Nitrospirae B. Fusobacteria C. Acidobacteria D. Bacteroidetes E. Proteobacteria

E. Proteobacteria The phylum Proteobacteria is comprised of heterotrophs, anoxygenic phototrophs, methylotrophs, sulfate reducers, nitrogen fixers, hydrogenotrophs, nitrifiers, iron, and sulfur oxidizers. As of 2014, there were more than 5,000 described species of Proteobacteria—about five times that of all the other Gram-negative phyla combined.

What do the phyla Bacteroidetes, Chlorobi, Fusobacteria, and Acidobacteria have in common? Choose one: A. They are obligate anaerobes. B. They are all pathogens acquired from soil. C. They stain acid-fast. D. They are all photosynthetic. E. They stain Gram-negative.

E. They stain Gram-negative. Bacteroidetes, Chlorobi, Fusobacteria, Acidobacteria, and Nitrospirae are all deeply branching phyla that stain Gram-negative. Nitrospira and Nitrobacter (a genus of alphaproteobacteria) are primarily responsible for environmental oxidation of nitrite to nitrate. Bacteroidetes and Chlorobi are obligate anaerobes, but inhabit different niches. Bacteroides spp. make up the major component of the human gut microbiome, while Chlorobi (e.g., Chlorobium) conduct anoxygenic photosynthesis. The phylum Fusobacteria contains human-pathogenic species, while Acidobacteria is a newly discovered phylum whose member species are widespread in soil but underrepresented in culture.

Which eukaryote-like organelles have been observed in Planctomycete cells? Choose one: A. flagella composed of microtubules B. Golgi apparatus C. chloroplasts D. mitochondria E. membrane-bound "nucleus" containing DNA

E. membrane-bound "nucleus" containing DNA Planctomycetes are characterized by unusual intracytoplasmic membranes that are reflective of similar structures in eukaryotes. As seen in this electron micrograph, a double membrane encloses the genetic material of this cell to form a type of nucleus. Others may also have a membrane-bound region termed an anammoxosome which contains enzymes for anaerobic ammonia oxidation.

A. heterocysts.

In the micrograph below of the filamentous cyanobacteria Nostoc, the lines are pointing to Choose one: A. heterocysts. B. akinetes. C. hormogonia. D. carboxysomes.

Cyanobacteria provide important environmental functions such as generating oxygen and fixing inorganic carbon (CO2) and nitrogen (N2) into biomass. However, some species, primarily those of the genus __________ , produce toxic compounds that can contaminate water supplies for entire cities.

Microcystis Cyanobacteria of the genus Microcystis produce the hepatotoxic (liver-damaging) compound microcystin. Periodic blooms of this organism occur in Lake Erie which serves as an important water supply for Toledo, Ohio. Other cyanobacteria can produce neurotoxins.

An example of a Gram-positive, anaerobic, spore-forming microbe is Choose one: A. Salmonella. B. Anabaena. C. Clostridium. D. Lactobacillus.

Only Clostridium satisfies all the conditions listed.

Please sort the following traits according to whether they are characteristic of all or only some cyanobacteria. - Autotrophy - Production of O2 - Chlorophyll a and b - Morphology - Ability to fix N2 - Habitat - Reproductive strategy

Shared: - Autotrophy - Production of O2 - Chlorophyll a and b Varies by species: - Morphology - Ability to fix N2 - Habitat - Reproductive strategy

Sort the phyla below according to whether they are associated with human health and disease, or whether they function primarily in nutrient cycling in the environment. -Chlorobi -Acidobacteria -Nitrospirae -Fusobacteria -Bacteroidetes

Soil and Water -Chlorobi -Acidobacteria -Nitrospirae Humans -Fusobacteria -Bacteroidetes The human gut microbiome is dominated by members of the Bacteroidetes. These bacteria produce extracellular enzymes that break down dietary plant material. Bacteroides spp. can, however, cause infections and abscesses in areas of the body outside of the gut. Members of the phylum Fusobacterium appear to be primarily pathogenic. In addition to causing skin ulcers, fusobacteria play a role in periodontal disease by facilitating multispecies biofilm formation. Chlorobi live in anoxic regions of lakes and oceans where they perform anoxygenic photosynthesis. In contrast, the Acidobacteria are abundant in soils. The type species is phototrophic and contains Chlorobi-like light-harvesting complexes (chlorosomes), while others are heterotrophic and can tolerate acid and elevated temperatures. Nitrospirae species are widespread and include members that oxidize nitrite (similar to proteobacterial nitrifiers) and others that are acidophilic iron oxidizers.

B. Borrelia. Borrelia burgdorferi, the causative agent of Lyme disease, can cause a bull's-eye rash.

The bull's-eye rash, can be caused by Choose one: A. Chlamydiae. B. Borrelia. C. Legionella. D. Bdellovibrio.

D. Myxobacterium The myxobacterium Stigmatella and the related species Myxococcus xanthus are free-living inhabitants of soils. They normally exist as single cells, however, under conditions of nutrient limitation, the cells aggregate to form a "multiceullar" stalk and fruiting body. Within the fruiting body, individual cells differentiate into myxospores, which become dispersed. When a myxospore encounters favorable conditions, it germinates and resumes vegetative growth. This lifecycle is similar to that of the eukaryotic cellular slime molds (e.g., Dictyostelium).

Which of the following organisms exhibits the lifestyle depicted here? Choose one: A. Rhizobium B. Streptomyces C. Mycobacterium D. Myxobacterium E. Clostridium

Many filamentous cyanobacteria (e.g., Oscillatoria seen here) disperse by producing short chains of cells known as _________ , while other species (e.g., Anabaena) can also produce _________ in response to adverse environmental conditions.

hormogonia; akinetes Hormogonia are short chains of motile cells which many filamentous cyanobacteria release to aid dispersal under conditions of nonlimiting nutrients. In contrast, conditions of low light, phosphate limitation, and cold temperatures can induce the formation of akinetes. These are spore-like resistant forms that may persist for decades before resuming vegetative growth when conditions improve.

Members of the phylum Actinobacteria have had a profound impact on human health over the course of civilization. One member of the genus ______ causes a deadly disease which has likely claimed over 1 billion victims, while another of the genus __________ yielded the first effective drug to combat this ancient scourge.

mycobacterium; streptomyces While Mycobacterium leprae is notorious for its disfiguring effects, the Actinobacterium Mycobacterium tuberculosis has likely killed more people than any other microbe in recorded history. Sometimes referred to as "consumption," tuberculosis is a serious chronic lung infection that eventually leads to a slow and wasting death. Tuberculosis was widespread in Europe during the eighteenth and nineteenth centuries, during which time Robert Koch established the bacterial etiology (in1882). Having been identified as infectious, public health measures (e.g., ordinances against spitting) were enacted to help prevent transmission. But the antibiotic streptomycin, isolated in 1943 from the actinomycete Streptomyces griseus, was the first drug to be effective in combatting the infection.

Imagine that a physician is treating a case of meningitis in a high school student. The responsible organism is proving difficult to culture, but preliminary DNA sequence analysis shows that it is a member of the Firmicutes phylum. The doctor confidently prescribes penicillin, and later vancomycin, neither of which result in any improvement in the patient's condition. Based on these results, the causative agent is most probably a species of _______

mycoplasma Antibiotics that inhibit cell wall synthesis (penicillin and vancomycin) are ineffective against species of Mycoplasma, all of which lack cell walls. In addition to meningitis, Mycoplasma causes a mild form of "walking pneumonia," and one species (M. genitalium) has been implicated in pelvic inflammatory disease.