Exam 24: Early Life and the Diversification of Prokaryotes

Mycoplasmas are bacteria that lack cell walls. On the basis of this structural feature, which statement concerning mycoplasmas should be true?

Use the information in the following paragraph to answer the next few questions. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan. -In which feature(s) should one be able to locate a complete chromosome of this bacterium? 1. nucleolus 2) prophage 3) endospore 4) nucleoid

If archaeans are more closely related to eukaryotes than to bacteria, then which of the following is a reasonable prediction?

The termite gut protist Mixotricha paradoxa has at least two kinds of bacteria attached to its outer surface. One kind is a spirochete that propels its host through the termite gut. A second type of bacteria synthesizes ATP, some of which is used by the spirochetes. The locomotion provided by the spirochetes introduces the ATP-producing bacteria to new food sources. Which of the following terms is (are) applicable to the relationship between the two kinds of bacteria? 1. mutualism 2) parasitism 3) symbiosis 4) metabolic cooperation

Which of the following obtain energy by oxidizing inorganic substances to obtain energy that is used, in part, to fix CO2?

Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free O2 reaches a critical concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces free O2. Consider the colonial aquatic cyanobacterium Anabaena, whose heterocytes are described as having "…a thickened cell wall that restricts entry of O2 produced by neighboring cells. Intracellular connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for carbohydrates." -Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen, what are two "strategies" that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen? 1. couple them with photosystem II (the photosystem that splits water molecules) 2) package them in membranes that are impermeable to all gases 3) be obligate anaerobes 4) be strict aerobes 5) package these enzymes in specialized cells or compartments that inhibit oxygen entry

The predatory bacterium Bdellovibrio bacteriophorus drills into a prey bacterium and, once inside, digests it. In an attack upon a gram-negative bacterium that has a slimy cell covering, what is the correct sequence of structures penetrated by B. bacteriophorus on its way to the prey's cytoplasm? 1. membrane composed mostly of lipopolysaccharide 2) membrane composed mostly of phospholipids 3) peptidoglycan 4) capsule

Jams, jellies, preserves, honey, and other foodstuffs with high sugar content hardly ever become contaminated by bacteria, even when the food containers are left open at room temperature. This is because bacteria that encounter such an environment

What is true of the amino acids that might have been delivered to Earth within carbonaceous chondrites?

Approximately how far back in time does the fossil record extend?

The thermoacidophile Sulfolobus acidocaldarius lacks peptidoglycan, but still possesses a cell wall. What is likely to be true of this species? 1. It is a bacterium. 2) It is an archaean. 3) The optimal pH of its enzymes will lie above pH 7. 4) The optimal pH of its enzymes will lie below pH 7. 5) It could inhabit certain hydrothermal springs. 6) It could inhabit alkaline hot springs.

Use the information in the following paragraph to answer the next few questions. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan. -This bacterium derives nutrition by digesting human intestinal contents (in other words, food). Thus, this bacterium should be an

In general, what is the primary ecological role of prokaryotes?

A fish that has been salt-cured subsequently develops a reddish color. You suspect that the fish has been contaminated by the extreme halophile Halobacterium. Which of these features of cells removed from the surface of the fish, if confirmed, would support your suspicion? 1. the presence of the same photosynthetic pigments found in cyanobacteria 2) cell walls that lack peptidoglycan 3) cells that are isotonic to conditions on the surface of the fish 4) cells unable to survive salt concentrations lower than 9% 5) the presence of very large numbers of ion pumps in its plasma membrane

Use the information in the following paragraph to answer the next few questions. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan. -Some of the proteins that allow this bacterium to swim are related (in an evolutionary sense) to proteins that

Which species is most likely to be found both in sewage treatment plants and in the guts of cattle?

In a hypothetical situation, the genes for sex pilus construction and for tetracycline resistance are located together on the same plasmid within a particular bacterium. If this bacterium readily performs conjugation involving a copy of this plasmid, then the result should be

Consider the thermoacidophile Sulfolobus acidocaldarius. Which of the following graphs most accurately depicts the expected temperature and pH profiles of its enzymes? (Note: The horizontal axes of these graphs are double, with pH above and temperature below.)

Which two processes are responsible for the shape of the curve at Time B? 1. transduction 2) entry of single-stranded Hfr DNA 3) rolling circle replication of single-stranded Hfr DNA 4) activation of DNA pumps in plasma membrane

Which species is probably an important contributor to the base of aquatic food chains as a primary producer?