Chapter 10

A sequence in rRNA that characterizes either a certain species or a group or related organisms is called a ________ sequence.

Signature

The basic taxonomic unit is the ________

Species

Streptococcus pneumoniae

Sputum showing numerous white blood cells and Gram-positive diplococci

Taxonomy can be viewed as three separate but interrelated areas. Match. Nomenclature

System of assigning names to organisms

Place the steps in the correct order to compare the restriction fragment length polymorphisms (RFLPs) of bacterial strains. 1. Extract DNA from each strain 2. Use gel electrophoresis to separate the DNA fragments 3. Use a restriction enzyme to digest the DNA 4. Visualize and compare the banding patterns to determine if the strains are different

1. Extract the DNA from each strain 3. Use a restriction enzyme to digest the DNA 2. Use gel electrophoresis to separate the DNA fragments 4. Visualize and compare the banding patterns to determine if the strains are different

Place the following taxonomic categories in the correct order from largest (most inclusive) to the smallest.

1. Phylum 2. Class 3. Order 4. Family 5. Genus 6. Species

In taxonomy, the most useful rRNA is the _________ rRNA in prokaryotes and the ________ rRNA in eukaryotes.

16S, 18S

Place in order the events that occur when performing phage typing. 1. Drops of different bacteriophages are spotted onto the agar surface 2. The test organism is inoculated into melted, cooled agar, which is then poured onto an agar plate 3. The pattern of clearing may be different for different bacterial strains and can be used for identification 4. If the organisms is susceptible to a specific phage, a clear area in the later of host cells will form where the phage was placed

2, 1, 4, 3

You have a sample containing bacteria that cannot yet be grown in culture. You decide to use 16S rDNA sequences to identify the bacteria. What is the correct order of steps you should use? 1. Amplify the bacterial DNA 2. Extract DNA from the bacteria 3. Sequence the 16S rDNA 4. Compare the 16S rDNA sequence with sequences of known organisms

2. Extract DNA from the bacteria 1. Amplify the bacterial DNA 3. Sequence the 16S rDNA 4. Compare the 16S rDNA sequence with sequences of known organisms

A dichotomous key is a ________ A. a flowchart of tests that each yield a positive or negative result to aid in identifying bacteria B. specific test that reveals answers about a bacterium of interest C. a series of tests that unlocks information about a bacterium not observable in its phenotype

A

Consider two organisms that diverged from a common ancestor at some point in history. If there are many differences in the sequences of their DNA, this indicates they diverged ________; if there are few differences, this indicates they diverged _________ A. longer ago; more recently B. more recently; longer ago

A

Determining the phylogeny, or evolutionary relatedness, of members of which of the following groups would likely be the least difficult? A. Animals B. Archaea C. Bacteria D. Protists

A

In a clinical lab, microscopic examination of a specimen is often enough to diagnose ________ because of their size and characteristic shape. A. certain infections by eukaryotic parasites B. infections by Gram positive fungi C. all bacterial infections

A

Phage typing relies on which of the following? A. differences in susceptibility of different strains of a given species of bacteria to bacteriophages B. whether or not a bacterial strain is able to express genes for phage production C. the amount of time it takes bacteriophages to infect a particular strain of bacteria D. the ability of some bacterial strains to produce phage structures

A

All of the following are examples of biochemical tests, except: A. serology B. catalase C. gelatinase D. sugar fermentation E. oxidase

A (serology actually relies on the binding of specific antibodies to characteristic proteins or polysaccharides that make up a prokaryote, not on specific metabolic properties)

In higher organisms such as plants and animals, the basic taxonomic unit of species is considered to be organisms that ________ A. Are morphologically similar B. Can interbreed to produce fertile offspring C. Occupy the same habitat D. Consume the same resources

A, B

Which of the following accurately describe biochemical tests used to identify microorganisms? A. They generally provide a more certain identification than just relying on colony morphology B. They rely on differences in metabolic capabilities of microorganisms C. They all look at the ability of bacteria to ferment various sugars D. They are always conducted quickly, with results found in just minutes E. They give results that are definitive for a specific microorganism

A, B

Which of the following help to explain why it is more difficult to determine the phylogeny of prokaryotes than that of plants and animals? A. The definition of species does not apply to prokaryotes in the same way as it does to plants and animals B. Prokaryotes have few differences in size and shape C. Prokaryotes cannot be classified at the species level D. There are many more plants and animals to compare

A, B

A probe used to identify a microorganism _________. A. has a detectable tag or label B. is a single-stranded piece of nucleic acid C. is complementary to the sequence of interest D. is a long sequence of nucleotides, at least 1,000 E. is a double-stranded piece of nucleic acid

A, B, C

Which of the following accurately describe DNA probes? A. they are labeled so that we can observe them via characteristics such as fluorescence B. they rely on complementary base pairing in order to bind their target DNA C. they allow us to look for specific known sequences of DNA D. they allows us to identify specific sequences of proteins E. they are short, single-stranded pieces of DNA of a particular sequence of interest

A, B, C, E

Which of the following accurately describe the DNA probes? A. They are labeled so that we can observe them via characteristics such as fluorescence B. They allow us to look for specific known sequences of DNA C. They allow us to identify specific sequences of proteins D. They rely on complementary base pairing in order to bind their target DNA E. They are short, single-stranded pieces of DNA of a particular sequence of interest

A, B, D, E

When diagnosing Helicobacter pylori infections, the urea breath test is preferred because ________ than other options. A. it is cheaper and faster B. it cultures the organism better C. it is less invasive D. it is more invasive

A, C

Antibiotic susceptibility patterns, like the one shown, are called ________.

Antibiograms

A strain is ________ A. another word for species B. one of a group of related isolates within a species C. the same as a genus D. a species that has been identified E. a commonly cultured bacterium of medical importance

B

Deduced amino acid sequences from ________ are now used as a basis for determining relatedness. A. sequences of PCR products B. whole and partial genome sequences C. 16S rDNA sequences

B

When two prokaryotic strains are compared by DNA hybridization, what is the minimum percent similarity they need to show to generally be considered members of the same species? A. 90% B. 70% C. 50% D. 100% E. 99%

B

Which of the following is a limitation of using ribosomal DNA sequence analysis for determining the phylogeny of organisms? A. because their function is basic to all of life, horizontal gene transfer events appear relatively common in ribosomal RNA genes B. sequence analysis of 16S rDNA is often unreliable for distinguishing closely related species C. the technique can only be used on organisms that can be grown in culture, which excludes most prokaryotes

B

Why are pH indicators used in so many biochemical tests that aim to identify bacteria? A. It is important to ensure that the bacteria are grown at their most appropriate pH range B. Many of the metabolic pathways being tested have acidic or basic end products, yielding a change in pH of the medium C. The pH indicator maintains the medium at the optimal pH for growth of the bacteria

B

What method are researchers today most likely to use in order to group organisms into a classification scheme? A. Serology B. 16S rDNA sequence data C. Microscopic morphology D. Metabolic capabilities

B (this approach has largely replaced classification schemes that grouped organisms by phenotype)

Which of the following correctly describe the relationships between genera of bacteria and their means for obtaining nutrients from plants? A. Rhizoblum species are plant pathogens that cause tumor-like growths B. Rhizoblum species form a mutually beneficial relationship with certain types of plants C. Agrobacterium species are plant pathogens that cause tumor-like growths D. Agrobacterium species form a mutually beneficial relationship with certain types of plants

B, C

Describe some growth conditions or characteristics that enable Pseudomonas aeruginosa to be a problem in hospital environments. A. ability to ferment carbohydrates B. resistant to antibiotics C. ability to grow in nutrient-poor environments D. resistant to disinfectants

B, C, D

What are advantages of using amino acid sequences deduced from whole and partial genome sequences as a basis for determining relatedness? A. there are a lot more whole genome sequences available than 16S rDNA sequences B. it accounts for novel organisms not detected by standard techniques used to amplify SSU rDNA C. ribosomal protein sequences are less conserved than their nucleic acid sequences D. each organism has an assortment of different ribosomal proteins, allowing more comparisons of gene products

B, D

Hydrogen-oxidizing bacteria such as Aquifex and Hydrogenobacter are ________ A. obligate chemoorganotrophs B. obligate chemolithotrophs C. Gram-positive D. thermophilic E. Gram-negative

B, D, E

What are some difficulties in using phenotypic characterizations for the phylogenetic classification of prokaryotes? A. Staining characteristics are difficult and time-consuming to obtain B. Organisms that appear dissimilar may be closely related C. There are insufficient numbers of tests for metabolic capabilities D. Phenotypically similar organisms may be only distantly related E. Phenotypic differences can be due to only a few gene products

B, D, and E

You are working in a clinical lab and are given a stool sample to analyze for suspected roundworms. What phenotypic characterization approach would give you the fastest presumptive answer? A. Culture characteristics B. Microscopic morphology C. Metabolic capabilities

B. Microscopic morphology Microscopic morphology allows a quick determination in cases where a specific organism is suspected, e.g., roundworms or a vaginal yeast infection

Why are ribosomal components (ribosomal RNA and ribosomal proteins) considered reliable indicators of evolutionary relatedness? A. Ribosomal genes have accumulated numerous mutations B. Ribosomes perform crucial and functionally constant tasks C. Ribosomes are present in all organisms D. Ribosomal genes are not commonly horizontally transferred E. Ribosomes are very different from one organism to the next

B. Ribosomes perform crucial and functionally constant tasks C. Ribosomes are present in all organisms D. Ribosomal genes are not commonly horizontally transferred

The method used to characterize different strains of bacteria that relies on differences in their susceptibility to ________ is called phage typing.

Bacteriophages

A group of strains that have a characteristic biochemical pattern is called a ________, or biotype

Biovar

The urea ________ test is a biochemical test done on a patient to determine whether he or she is infected with Helicobacter pylori, a common cause of stomach ulcers.

Breath

All of the statements about GC content of prokaryotes are true except: A. the GC content is expressed as the percent of guanine plus cytosine B. because of base-pairing rules, in double-stranded DNA, the number of adenines equals the number of thymines C. if the GC content of two organisms is identical or nearly the same, the organisms are closely related D. if the GC content of two organisms differs by more than a small percentage, they cannot be closely related

C

Consider the urease tests shown. The tube on the right is uninoculated control (yellow). What does the tube on the left (pink) tell us? A. The tube on the left is a negative result B. Both tubes demonstrate urease production via different pathways, hence the different colors shown C. The tube on the left is a positive result for urease production D. The microorganism in the left tube consumed all the urease

C

Pseudomonas species are Gram-negative rods that, unlike members of the family Enterobacteriaceae, are _________. A. obligate fermenters with polar flagella B. obligate anaerobes C. oxidase-positive non-fermenters

C

The designation O157:H7 of E. coli is an example of which of the following? A. Phage typing B. Antibiograms C. Serological typing D. Molecular typing E. Biochemical typing

C

When comparing two organisms using DNA hybridization, the process relies on what property of DNA? A. Only DNA extraced from the same species will hybridize B. The DNA from each organism must have exactly the same sequence of nucleotides C. The extent of hybridization reflects the degree of sequence similarity between the two organisms D. The result is determined by the total amount of DNA from each organism

C

Which is a nucleic acid amplification test (NAAT)? A. serological tests B. sequencing ribosomal RNA genes C. polymerase chain reaction D. fluorescence in situ hybridization

C

Which of the following results indicate that the bacterial strain being tested is susceptible to a specific bacteriophage? A. a hazy area on the clear layer of bacterial cells being tested B. a growth much like a colony on top of the layer of bacterial cells being tested C. a clear area on the hazy layer of bacterial cells being tested

C

Which of the following accurately describe biochemical tests used to identify microorganisms? A. They are always conducted quickly, with results found in just minutes B. They all look at the ability of bacteria to ferment various sugars C. They generally provide a more certain identification than just relying on colony morphology D. They rely on differences in metabolic capabilities of microorganisms E. They give results that are definitive for a specific microorganism

C, D

The _________ test detects the ability of the organism to produce an enzyme that breaks down hydrogen peroxide to form O2 and water

Catalase

More than 300 cases of salmonellosis occur within a large city. Each time, Salmonella enterica is isolated from the feces of the patient. Based on that information, the news media report that there must be a common source to all these cases. What additional information would be needed to support or disprove this view? A. More patients would need to be identified and Salmonella enterica isolated from their feces B. Additional cases would need to be found in other cities for comparision C. More time would be needed to track additional new cases D. The specific strain of the Salmonella would need to be identified

D. The specific strain of the Salmonella would need to be identified

_________ media are designed to reveal specific colony characteristics that can help in the initial identification of bacteria in clinical samples.

Differential

The base ratio of an organism is usually expressed as the percent of guanine plus cytosine, which is called the ________ content.

GC

Neisseria gonorrhoeae

Gram-negative diplococci clustered in white blood cells in a sample of urethral secretion from a man

In the case of endospore-forming bacteria, the _________ of the endospore within a cell can be used to aid in identification of the organism.

Location

Members of the genus ________, such as the causative agents of tuberculosis and Hansen's disease, are examples of acid-fast organisms.

Mycobacterium

Microscopic morphology, culture characteristics, and fatty acid analysis are all examples of ________ characteristics used to identify prokaryotes.

Phenotypic

The evolutionary relatedness of organisms is called _________

Phylogeny

Taxonomy can be viewed as three separate but interrelated areas. Match. Classification

Process of arranging organisms into similar or related groups, primarily to make it easier to identify and study them

Taxonomy can be viewed as three separate but interrelated areas. Match. Identification

Process of characterizing an isolate to determine the group (taxon) to which it belongs

The ________ bacteria have projections called prosthecae, which are extensions of the cytoplasm and cell wall that increase the surface area to facilitate absorption of nutrients.

Prosthecate

A group of strains that have cell surface antigens different from other strains is called a ________, or serotype.

Serovar

T/F: Some methods of detecting specific nucleotide sequences make it possible to identify organisms that cannot yet be grown in culture.

True (considering that the vast majority of prokaryotes have never been cultivated, this is a huge benefit of this type of approach)

The genes that encode ribosomal RNA (rRNA) are ________

rDNAs