Chapter 28: Bacteria and Archaea

Question 1

Discuss the biological impact, abundance and habitat diversity of bacteria and archaea collectively.

Answer 1

Only 5000 species of bacteria and archaea have been named and described, but biologists are virtually certain that millions exist.

Question 2

On a blank sheet of paper draw a large version of Figure 28.1, a phylogenetic tree of the three domains of life. Using information from Table 28.1, add labelled marks to your tree indicating where the following traits evolved: circular chromosome, linear chromosome, membranes with straight fatty acids (MSFA’s), membranes with branched fatty acids (MBFA’s), cell wall with peptidoglycan (CW+P), cell wall without peptidoglycan (CW-P), DNA with histones, nuclear envelope.

Answer 2

v

Question 3

Use your textbook or another resource to characterize the size differences between the three domains of life.

Answer 3

1

Question 4

Was the common ancestor of all species alive today a eukaryote, a bacterial prokaryote, or an archaeal prokaryote? Explain your reasoning.

Answer 4

1

Question 5

Some bacteria cause diseases of multicellular eukaryotes. List the four criteria Koch postulated necessary to establish a causative link between a particular microorganism and a specific disease

Answer 5

1. The microbe must be present in individuals suffering from the disease and absent from healthy individuals.
2. The organism must be isolated and grown in a pure culture away from the host organism.
3. If organisms from the pure culture are injected into a healthy experimental animal, the disease symptoms should appear.
4. The organism should be isolated from the diseased experimental animal, again grown in pure culture, and demonstrated to be the same as the original organism.

Question 6

What are antibiotics and where do we source them?

Answer 6

soil bacteria

Bacillus brevis

Question 7

Relate the niche concept to enrichment cultures used to grow bacteria in laboratories

Answer 7

• cells are sampled from the environment and grown under specific conditions temperature, lighting, substrate, types of available food, etc.
• Cells that thrive under the specified conditions will increase in numbers enough to be isolated and studied in detail.

Question 8

Describe how direct sequencing is used to identify bacteria and archaea that have never been isolated or seen.

Answer 8

Direct sequencing is a new technique for documenting the presence of bacteria and archaea that have never been seen because they cannot be grown in pure culture. is based on identifying phylogenetic species

Question 9

Use a table to summarize the morphological diversity of bacteria and archaea.

Answer 9

extensive morphological diversity in terms of size, shape, and motility. Bacteria range in shape from filaments, spheres, rods, and chains to spirals. Bacteria have a range of modes of motility.

Question 10

Explain how Gram staining is used to broadly categorize bacterial species based on their cell wall structure.

Answer 10

2 general types of cell wall exist that can be distinguished by treatment with a dye called the Gram stain.

1. Gram-positive cells have a cell wall containing an extensive amount of a carbohydrate called peptidoglycan. (which look purple under a microscope) retain Gram stain better than
2. Gram-negative cells (which look pink). have a cell wall with two components, a thin layer containing peptidoglycan and an outer phospholipid bilayer.

Question 11

Use a table to summarize the metabolic diversity of bacteria and archaea.

Answer 11

• all require chemical energy - ATP & carbon compounds
• Must use one of three sources of energy: light, organic molecules, or inorganic molecules.
• Autotrophs manufacture their own carbon-containing compounds.
• Heterotrophs live by consuming them

Question 12

It can be argued that oxygen is toxic to life. What was the oxygen revolution and what is a major advantage for organisms that evolved the capacity to utilize oxygen?

Answer 12

Oxygen is highly electronegative and so is an efficient electron acceptor. Much more energy is released as electrons move through ETCs with oxygen as the ultimate acceptor than is released with other acceptor substances.

Question 13

Explain the significance of certain bacteria and archaea to the ecological cycling of nitrogen.

Answer 13

The nitrite (NO2) that some bacteria produce as a by-product of respiration does not build up in the environment but rather is used as an electron acceptor by other species and converted to molecular nitrate (NO3), which in turn is converted to molecular nitrogen (N2) by yet another suite of bacterial and archaeal species

Question 14

Explain how human dependence on some crop plants that do not form symbiotic associations with nitrogen-fixing bacteria has led to a serious pollution problem in aquatic ecosystems.

Answer 14

The widespread use of ammonia fertilizers is causing serious pollution. When ammonia is added to the soil, much of it is used by bacteria as food, which then release nitrite (NO2–) or nitrate (NO3–). Nitrates cause pollution in aquatic environments. In an aquatic ecosystem, nitrates can decrease the oxygen content, causing anaerobic “dead zones” to develop.

Question 15

Read Canadian Research 28.1 Is There a Universal Tree of Life on pages 563-564. Use a description of lateral gene transfer in bacteria and archaea to argue why prokaryotic genomes are chimeras.

Answer 15

lateral gene transfer between prokaryotic cells is common, up to a third of genomic variation within prokaryotic species may be due to gene transfer and gene loss

chimeras—containing genes obtained from many sources other than their direct ancestors

Question 16

Today at least sixteen phyla of bacteria are recognized. For each of the six bacterial lineages highlighted in our textbook, list one or two human or ecological impacts. Firmicutes

Answer 16

Firmicutes

• Gram positives and most are rod shaped or spherical.
• metabolically diverse.
• important components of soil.
• Some species in this group cause diseases, yet we use some to ferment milk into yogurt.

Question 17

Today at least sixteen phyla of bacteria are recognized. For each of the six bacterial lineages highlighted in our textbook, list one or two human or ecological impacts. Spirochaetes

Answer 17

Spirochaeles (spirochetes) are distinguished by their corkscrew shape and unusual flagella.

• Most spirochetes produce ATP via fermentation.
• common in aquatic habitats.
• Spirochetes cause the diseases syphilis and Lyme disease

Question 18

Today at least sixteen phyla of bacteria are recognized. For each of the six bacterial lineages highlighted in our textbook, list one or two human or ecological impacts. Actinobacteria

Answer 18

Actinobacteria

• Gram positive
• shape varies from rods to filaments
• soil-dwelling species are found as chains of cells that form extensive branching filaments called mycelia.
• Many species heterotrophs.
• Some species live as decomposers in soil;
• some live in association with plant roots and fix nitrogen.
• Tuberculosis and leprosy are caused by members of this group. Species from the genus Streptomyces produce over 500 distinct antibiotics.

Question 19

Today at least sixteen phyla of bacteria are recognized. For each of the six bacterial lineages highlighted in our textbook, list one or two human or ecological impacts. Chlamydiae

Answer 19

Chlamydiae

• spherical and very tiny.
• endosymbionts—they live as parasites inside animal cells and get almost all of their nutrition from their hosts.
• cause blindness and urogenital tract infections in humans.

Question 20

Today at least sixteen phyla of bacteria are recognized. For each of the six bacterial lineages highlighted in our textbook, list one or two human or ecological impacts. Cyanobacteria

Answer 20

Cyanobacteria were formerly known as “blue-green algae.”

• They are found as independent cells, chains, or colonies.
• All perform oxygenic photosynthesis
• produce oxygen, nitrogen, and organic compounds that feed other organisms in aquatic environments.

Question 21

Today at least sixteen phyla of bacteria are recognized. For each of the six bacterial lineages highlighted in our textbook, list one or two human or ecological impacts. Proteobacteria

Answer 21

Proteobacteria form five major subgroups and are very diverse in morphology and metabolism.

• Some proteobacteria can form colonies, which can produce a structure called a fruiting body.
• Pathogenic proteobacteria cause Legionnaire’s disease, cholera, dysentery, and gonorrhea.

Question 22

Explain why the Archaea are misnamed

Answer 22

Domain Archaea is composed of at least three major lineages: the Crenarchaeota, Euryarchaeota, and Korarchaeota. These three groups are highly differentiated at the DNA sequence level, but almost nothing is know about the Korarchaeota .

Question 23

Although future research is likely to reveal multiple phyla of Archaea, our textbook explains there are presently three major phyla recognized. For the two phyla on page 568, list one or two human, or ecological impacts. Crenarchaeota

Answer 23

Crenarchaeota

• shaped like filaments, rods, discs, or spheres.
• metabolically diverse, although some make ATP only through fermentation.
• They are the only life-forms present in certain extreme environments, such as high-pressure, very hot, cold, or acidic environments.

Question 24

Although future research is likely to reveal multiple phyla of Archaea, our textbook explains there are presently three major phyla recognized. For the two phyla on page 568, list one or two human, or ecological impacts. Euryarchaeota

Answer 24

The Euryarchaeota come in many shapes.

• They live in every conceivable habitat, including high-salt, high-pH, and low-pH environments.
• They include the methanogens, which contribute about 2 billion tons of methane to the atmosphere each year.

Question 25

________ use light energy to promote electrons to the top of electron transport chains. ATP is then produced by photophosphorylation.

Answer 25

Phototrophs

Question 26

____________ oxidize organic molecules with high potential energy. ATP may be produced by cellular respiration using sugars as electron donors or by fermentation pathways.

Answer 26

Chemoorganotrophs

Question 27

____________ oxidize inorganic molecules with high potential energy. ATP is produced by cellular respiration with inorganic compounds serving as the electron donor.

Answer 27

Chemolithotrophs

Question 28

________________, a lineage of photosynthetic bacteria, were the first organisms to perform oxygenic (oxygen-producing) photosynthesis.

Answer 28

Cyanobacteria

Question 29

____________ can be shaped like filaments, rods, discs, or spheres.

Answer 29

Crenarchaeota

Question 30

Domain Archaea is composed of at least three major lineages:

Answer 30

the Crenarchaeota, Euryarchaeota, and Korarchaeota.

Question 31

____________ were formerly known as “blue-green algae.” They are found as independent cells, chains, or colonies.

Answer 31

Cyanobacteria

Question 32

__________________ are distinguished by their corkscrew shape and unusual flagella.

Answer 32

Spirochaeles (spirochetes)

Question 33

_____________ are Gram positives and most are rod shaped or spherical.

Answer 33

Firmicutes