Ch 26 HW

Azotobacter is a genus of bacteria that live in soil and have the following characteristics: -They are bacilli. -They are gram-negative. -They are obligate aerobes. -They can fix nitrogen. (Unlike some other nitrogen-fixing bacteria, which associate with the roots of plants, Azotobacter species are free-living.) Select the four statements that are true for bacteria in the genus Azotobacter.

-They can convert atmospheric nitrogen to ammonia. -They have a relatively thin layer of peptidoglycan in their cell wall. -They use O2 for cellular respiration. -They are shaped like rods

Which of the following statements about phylogenetic trees is true?

A paraphyletic group consists of a common ancestor and some of its descendants.

A biologist trying to determine the mechanism of adenosine triphosphate (ATP) production in a newly discovered bacterium provides several different substrates on which the bacteria can feed. Which of the following results would indicate that the species uses fermentation to produce ATP?

After exposure to amino acids, the bacteria produce a smell like rotting flesh.

A water sample from a hot thermal vent contained a single-celled organism that had a cell wall but lacked a nucleus. What is its most likely classification?

Archaea

Classify each statement or picture as applying to gram-positive bacteria, gram-negative bacteria, or both.

Gram-positive bacteria: -appear purple after Gram staining -have a thick peptidoglycan layer -alcohol rinse does not remove crystal violet Gram-negative bacteria: -appear pink after Gram staining -have thin peptidoglycan layer -alcohol rinse easily removes crystal violet -have an outer membrane as part of their cell wall structure both: -have a plasma membrane

Which of the following is an observed electron donor and its associated electron acceptor for the archaea that produce methane (swamp gas)?

H2 and CO2

When using Koch's postulates, which of the following is an essential requirement for the suspected pathogen?

It is present in all organisms with the disease.

The text claims that the evolution of an oxygen atmosphere paved the way for increasingly efficient cellular respiration and higher growth rates in organisms. Explain

Large amounts of potential energy are released when oxygen is the electron acceptor, because oxygen is so electronegative. The large amount of energy is required for large body size and high growth rates.

Which of the following types of metabolism are found in archaea or bacteria but not found in eukaryotes?

Methanogenesis Only some archaea can generate methane utilizing H2 as an electron donor and CO2 as an electron acceptor

Why do species that release H2S as a by-product often live side by side with species that use H2S as an electron donor?

One species provides the necessary chemical for the other to survive. Without H2S the second species could not survive.

What distinguishes bacteria from archaea?

Only bacteria have peptidoglycan in their cell walls.

What is lateral gene transfer?

Physical transfer of a gene from a species in one lineage to a species in another lineage.

What characteristics were used to classify organisms before Woese's tree of life analysis?

Presence of a membrane-bound nucleus

Which group was not described in Woese's tree of life analysis?

Prokarya

Which molecule did Carl Woese study to produce his tree of life?

Ribosomal RNA

Aquatic nitrate pollution can result in _____.

an algal bloom that, when the algae die and are decomposed by bacteria, leads to hypoxia and the death of fish

Which of these are the two major sources of nitrate pollution in rivers?

animal wastes and fertilizers

Organisms that synthesize their own C-C molecules from single-carbon starting materials are named _____, while those that absorb preformed C-C compounds produced by other organisms are _____.

autotrophs; heterotrophs Autotrophs are "self-feeders," while heterotrophs are "other-feeders."

You might be interested to know how many different types of bacteria live on the shower curtain in your bathroom. What is the most efficient method for finding out?

direct sequencing

You need to identify the major type of bacteria living on the shower curtain in your bathroom and find out what they use as a food source. What is the most efficient method for answering this question?

enrichment culture

What do some photosynthetic bacteria use as a source of electrons instead of water?

hydrogen sulfide (H2S)

The purple non-sulfur bacterium Rhodospirillum grows best as a photoheterotroph. What are the most favorable sources of energy and carbon for this bacterium?

light and fructose

During cellular respiration, some bacteria use methane (CH4) as an electron donor and oxygen (O2) as an electron acceptor. What is the name for this group of bacteria?

methanotrophs

Cyanobacteria are thought to be the first organisms to evolve ____.

oxygenic photosynthesis Cyanobacteria use light energy to split or oxidize water, with oxygen gas as a by-product. The electrons are passed through an electron transport chain and used to make NADPH and ATP.

Microbiologists use the Gram stain to aid in the identification of bacteria. What is the major difference between Gram-positive and Gram-negative bacteria?

presence or absence of outer plasma membrane

What organisms are most numerous on Earth?

prokaryotes

Molecular phylogenies were first used to separate bacterial and archaeal lineages based upon the sequence data from which of the following molecules?

ribosomal small subunit RNA

The Gram stain, commonly used to classify a bacterial isolate into one of two groups, is based upon the characteristics of which of the following structures?

the cell wall

Which of the following describe all existing bacteria?

tiny, ubiquitous, metabolically diverse

True or false? Data showing that the Bacteria were the first lineage to diverge from the common ancestor of all living organisms suggest that the Archaea and Eukarya are more closely related to each other than they are to the Bacteria.

true

If two species of bacteria use glucose as an electron donor, but species A uses oxygen as the final electron acceptor and species B uses nitrate, then how much glucose would species B need to use to generate the same amount of ATP as species A?

~60% more glucose There is a bit less free energy available for species B to capture than species A.