Bacteria and Archaea

The mean (\(\overline x \,\)) of a variable is the sum of the data values divided by the number of observations (n):

                                                     \(\overline x \, = \,\frac{{\sum {{x_i}} }}{n}\)

In this formula, \({x_i}\) is the value of the i th observation of the variable; the \(\sum {} \) symbol indicates that the n values of x are to be added together. Calculate the mean for each treatment.

Genetic variation in bacterial populations cannot result from

(A) transduction

(B) conjugation

(C) mutation

(D) meiosis

A pathogenic bacterium’s toxin causes symptoms that increase the bacterium’s chance of spreading from host to host. Does this information indicate whether the poison is an exotoxin or endotoxin? Explain.

Photoautotrophs use 

(A) light as an energy source and CO₂ as a carbon source.

(B) light as an energy source and methane as a carbon source.

(C) N₂ as an energy source and CO₂ as a carbon source.

(D) CO₂ as both an energy source and a carbon source.

Which of the following statements is not true? 

(A) Archaea and bacteria have different membrane lipids.

(B) The cell walls of archaea lack peptidoglycan.

(C) Only bacteria have histones associated with DNA.

(D) Only some archaea use CO₂ to oxidize H₂, releasing methane.

The standard error (SE), which indicates how greatly the mean would likely vary if the experiment was repeated, is calculated as:\({\rm{SE}} = \,\frac{s}{{\sqrt n }}\). 

As a rough rule of thumb, if an experiment were to be repeated, the new mean typically would lie within two standard errors of the original mean (that is, within the range of \(\overline x \, \pm \,2{\rm{SE}}\)). Calculate \(\overline x \, \pm \,2{\rm{SE}}\)for each treatment, determine whether these ranges overlap, and interpret your results.

Which of the following involves metabolic cooperation among prokaryotic cells? 

(A) binary fission 

(B) endospore formation 

(C) biofilms 

(D) photoautotrophy

Bacteria perform the following ecological roles. Which role typically does not involve symbiosis? 

(A) skin commensalist 

(B) decomposer 

(C) gut mutualist 

(D) pathogen

Plant like photosynthesis that releases O₂ occurs in

(A) cyanobacteria.

(B) archaea.

(C) gram-positive bacteria.

(D) chemoautotrophic bacteria.

Nitrogenfixing bacterium Rhizobium infects the roots of some plant species, forming a mutualism in which the bacterium provides nitrogen, and the plant provides carbohydrates. Scientists measured the 12-week growth of one such plant species (Acacia irrorata) when infected by six different Rhizobium strains.

(a) Graph the data. (b) Interpret your graph.

In a short essay (about 100–150 words), discuss how prokaryotes and other members of hydrothermal vent communities transfer and transform energy.

Explain how the small size and rapid reproduction rate of bacteria(such as the population shown here on the tip of a pin) contribute to their large population sizes and high genetic variation.

Explain how molecular systematics and metagenomics have contributed to our understanding of the phylogeny and evolution of prokaryotes

What would the discovery of a bacterial species that is a methanogen imply about the evolution of the methane-producing pathway?

Explain how prokaryotes, though small, can be considered giants in their collective impact on Earth and its life.

MAKE CONNECTIONS Review Figure 10.6. Then summarize the main steps by which cyanobacteria produce O₂ and use CO₂ to make organic compounds.

Identify at least two ways that prokaryotes have affected you positively today.

Describe two adaptations that enable prokaryotes to survive in environments too harsh for other organisms.

Contrast the cellular and DNA structures of prokaryotes and eukaryotes.

Suggest a hypothesis to explain why the thylakoid membranes of chloroplasts resemble those of cyanobacteria. Refer to Figures 6.18 and 26.21.

          Figure 26.21

      Figure 6.18

Although rare on a per gene basis, new mutations can add considerable genetic variation to prokaryotic populations in each generation. Explain how this occurs.

Distinguish between the three mechanisms by which bacteria can transfer DNA from one bacterial cell to another.

In a rapidly changing environment, which bacterial population would likely be more successful: one that has individuals capable of conjugation or one that does not? Explain.

If a nonpathogenic bacterium were to acquire resistance to antibiotics, could this strain pose a health risk to people? In general, how does DNA transfer among bacteria affect the spread of resistance genes?

Distinguish between the four major modes of nutrition, noting which are unique to prokaryotes.

A bacterium requires only the amino acid methionine as an organic nutrient and lives in lightless caves. What mode of nutrition does it employ? Explain.

Describe what you might eat for a typical meal if humans, like cyanobacteria, could fix nitrogen.