Chapter 01: Bacterial Cell Structure, Physiology, Metabolism, and Genetics
Mahon: Textbook of Diagnostic Microbiology, 7th Edition

MULTIPLE CHOICE

	1.	To survive, microbial inhabitants have learned to adapt by varying all of the following, except
a.	growth rate.	
b.	growth in all atmospheric conditions.	
c.	growth at particular temperatures.	
d.	bacterial shape.	

ANS:	D
The chapter begins by discussing the way microbial inhabitants have had to evolve to survive in many different niches and habitats. It discusses slow growers, rapid growers, and replication with scarce or abundant nutrients, under different atmospheric conditions, temperature requirements, and cell structure. Bacterial shape as a form of evolution is not discussed.

OBJ:	Level 2: Interpretation

	2.	Who was considered the father of protozoology and bacteriology?
a.	Anton van Leeuwenhoek	
b.	Louis Pasteur	
c.	Carl Landsteiner	
d.	Michael Douglas	

ANS:	A
The book discusses Anton van Leeuwenhoek as the inventor of the microscope and the first person to see the “beasties.” So they dubbed him the father of protozoology and bacteriology. The other three individuals were not discussed.

OBJ:	Level 1: Recall	

	3.	Prokaryotic cells have which of the following structures in their cytoplasm?
a.	Golgi apparatus	
b.	Ribosomes	
c.	Mitochondria	
d.	Endoplasmic reticulum	

ANS:	B
All the structures listed are found in eukaryotic cells, but ribosomes are the only ones that apply to prokaryotic cells.

OBJ:	Level 1: Recall	

	4.	This form of DNA is commonly found in eukaryotic cells.
a.	Linear	
b.	Circular	
c.	Plasmid	
d.	Colloid	

ANS:	A
Circular and plasmid DNA are usually found only in bacteria, not eukaryotic cells. Colloid is a property of protein molecules and is not associated with nucleotides.

OBJ:	Level 1: Recall	

	5.	The nuclear membrane in prokaryotes is
a.	missing.	
b.	impenetrable.	
c.	a classic membrane.	
d.	a lipid bilayer membrane.	

ANS:	A
Prokaryotic cells do not have any membrane-bound structures in the cytoplasm including a structured nucleus.

OBJ:	Level 1: Recall	

	6.	A microorganism that is a unicellular organism and lacks a nuclear membrane and true nucleus belongs to which classification?
a.	Fungi	
b.	Bacteria	
c.	Algae	
d.	Parasite	

ANS:	B
Fungi, algae, and parasites are unicellular eukaryotic organisms that contain a true nucleus. Bacteria are prokaryotic and do not contain a true nucleus or nuclear membrane.

OBJ:	Level 1: Recall	

	7.	In the laboratory, the clinical microbiologist is responsible for all the following, except
a.	isolating microorganisms.	
b.	selecting treatment for patients.	
c.	identifying microorganisms.	
d.	analyzing bacteria that cause disease.	

ANS:	B
Clinical microbiologists do not select the treatment for patients. They provide the doctor with the name of the organism and the antibiotics that can kill the bacteria, but not in the final selection of treatment protocols.

OBJ:	Level 2: Recall	

	8.	What enables the microbiologist to select the correct media for primary culture and optimize the chance of isolating a pathogenic organism?
a.	Determining staining characteristics	
b.	Understanding the cell structure and biochemical pathways of an organism	
c.	Understanding the growth requirements of potential pathogens at specific body site	
d.	Knowing the differences in cell walls of particular bacteria	

ANS:	C
By understanding growth requirements, a microbiologist can maximize the chance of the organism being isolated from a culture. The other three choices are used to identify a bacterium once it has grown on media.

OBJ:	Level 2: Interpretation

	9.	A clinical laboratory scientist is working on the bench, reading plates, and notices that a culture has both a unicellular form and a filamentous form. What type of organism exhibits these forms?
a.	Virus	
b.	Fungi	
c.	Bacteria	
d.	Parasite	

ANS:	B
Viruses typically only have one form and would not grow on plate media. Bacteria have two forms: a vegetative cell and spore form. Parasites may have trophozoite, cysts, egg, etc. Fungi are the organism classification that may have both unicellular yeast forms and filamentous hyphal forms in the same culture plate.

OBJ:	Level 2: Interpretation

	10.	All of the following statements are true about viruses, except:
a.	Viruses consist of DNA or RNA but not both.	
b.	Viruses are acellular but are surrounded by a protein coat.	
c.	Viruses can infect bacteria, plants, and animals.	
d.	Viruses do not need host cells to survive and grow.	

ANS:	D
Viruses need to have a host cell because they do not have the ability to reproduce or nourish themselves without the host’s cellular mechanisms.

OBJ:	Level 2: Interpretation

	11.	Diagnostic microbiologists apply placement and naming of bacterial organisms into all the following categories, except
a.	order.	
b.	family.	
c.	genus.	
d.	species.	

ANS:	A
Clinical microbiologists use the family, genus, and species taxonomic categories to identify species that are important for diagnostic diseases.

OBJ:	Level 1: Recall	

	12.	Bacterial species that exhibit phenotypic differences are considered
a.	biovarieties.	
b.	serovarieties.	
c.	phagevarieties.	
d.	subspecies.	

ANS:	D
Biovarieties vary based on biochemical test results, serovarieties vary based on serologic test results, and phagevarieties is a fictitious word.

OBJ:	Level 2: Interpretation

	13.	What structure is described as a phospholipid bilayer embedded with proteins and sterols that regulates the type and amount of chemicals that pass in and out of a cell?
a.	Cell wall	
b.	Mitochondria	
c.	Endoplasmic reticulum	
d.	Plasma membrane	

ANS:	D
The cell wall is the outer covering made up of lipids. The mitochondria is a cellular organelle that is considered the powerhouse of the cell (electron transport and oxidative phosphorylation occur here). The endoplasmic reticulum is a cellular organelle where protein synthesis occurs.

OBJ:	Level 1: Recall	

	14.	What makes the interior of the plasma membrane potentially impermeable to water-soluble molecules?
a.	The hydrophobic tails of the phospholipid molecules are found there.	
b.	The hydrophilic tails of the phospholipid molecules are found there.	
c.	The ion channels are found there.	
d.	The cholesterol molecules in the plasma membrane are found solely in the interior of the membrane.	

ANS:	A
The plasma membrane is designed so that the hydrophilic heads of the phospholipid molecules are positioned to make contact with the intracellular and extracellular fluids. The hydrophobic tails of the phospholipid molecules face away from the fluids and form the interior of the plasma membrane. The tails of the phospholipid molecules are hydrophobic, not hydrophilic. The ion channels extend through the cellular membrane. The cholesterol molecules also extend through the plasma membrane.

OBJ:	Level 2: Interpretation

	15.	The function of a cell wall is to
a.	regulate the transport of macromolecules in and out of the cell.	
b.	provide rigidity and strength to the exterior of the cell.	
c.	provide reserve energy to the eukaryotic cell.	
d.	protect the eukaryote from predators.	

ANS:	B
The plasma membrane regulates the transport of macromolecules in and out of the cell, not the cell wall. The mitochondria provide energy to the eukaryotic cell. Cell walls are not able to protect a eukaryotic cell from predators.

OBJ:	Level 1: Recall	

	16.	Name the numerous short (3 to 10 mm) projections that extend from the cell surface and are used for cellular locomotion.
a.	Flagella	
b.	Mitochondria	
c.	Cilia	
d.	Phospholipid	

ANS:	C
By definition, cilia are short projections extending from the cell surface and are used for locomotion, whereas flagella are longer projections used for locomotion. Mitochondria are cellular organelles responsible for electron transport and oxidative phosphorylation. Phospholipids are polar molecules that form the plasma membrane.

OBJ:	Level 1: Recall	

	17.	A microbiology technologist performs a traditional bacterial stain on a colony from a wound culture that is suspected to contain bacteria from the genus Clostridium. The unstained areas in the bacterial cell observed by the technologist are called
a.	cilia.	
b.	ribosomes.	
c.	endospores.	
d.	mitochondria.	

ANS:	C
Ribosomes are small circular areas used for protein synthesis that are not visible on a traditional stain. Cilia are short projections on the outside of the plasma membrane used for locomotion. Mitochondria are cellular organelles used for energy production.

OBJ:	Level 2: Interpretation

	18.	This constituent of a gram-positive cell wall absorbs crystal violet but is not dissolved by alcohol, thus giving the gram-positive cell its characteristic purple color.
a.	Mycolic acid	
b.	Cholesterol	
c.	Carbolfuchsin	
d.	Peptidoglycan	

ANS:	D
Mycolic acid is part of the cell wall of the Mycobacterium and Nocardia spp., but does not play a part in the Gram stain. Cholesterol is also part of the cell membrane, not the cell wall, so it does not play a part in the Gram stain. Carbolfuchsin is a stain used in bacteriology.

OBJ:	Level 2: Interpretation

	19.	Mycobacteria have a gram-positive cell wall structure with a waxy layer containing these two compounds.
a.	Glycolipids and mycolic acid	
b.	Glycolipids and phospholipids	
c.	Mycolic acid and lipopolysaccharides	
d.	Lipopolysaccharides and phospholipids	

ANS:	A
Glycolipids are a part of the waxy layer, but phospholipids are part of the plasma membrane. Mycolic acid is a part of the waxy layer, but lipopolysaccharides are part of a gram-negative cell wall. Lipopolysaccharides are part of a gram-negative wall, and phospholipids are part of a plasma membrane.

OBJ:	Level 1: Recall	

	20.	When performing a Gram stain on a gram-negative organism, the crystal violet is absorbed into this outer cell wall layer, and then washed away with the acetone alcohol. What is the main component of the outer layer of the cell wall?
a.	Peptidoglycan	
b.	Mycolic acid	
c.	N-Acetyl-D-muramic acid	
d.	Lipopolysaccharide	

ANS:	D
Peptidoglycan is a thinner layer under the lipopolysaccharide in a gram-negative organism, whereas mycolic acid is the waxy layer present in a mycobacterium’s outer cell wall, and N-acetyl-D-muramic acid is part of the peptidoglycan.

OBJ:	Level 1: Recall	

	21.	The three regions of the lipopolysaccharide include all the following, except
a.	antigenic O-specific polysaccharide.	
b.	mycolic acid.	
c.	core polysaccharide.	
d.	endotoxin (inner lipid A).	

ANS:	B
Antigenic O-specific polysaccharide, core polysaccharide, and endotoxin are all part of the lipopolysaccharide layer. Mycolic acid is a component of cell.

OBJ:	Level 1: Recall	

	22.	The outer cell wall of the gram-negative bacteria serves three important functions, which includes all the following, except:
a.	It provides an attachment site for the flagella, which will act in locomotion.	
b.	It acts as a barrier to hydrophobic compounds and harmful substances.	
c.	It acts as a sieve.	
d.	It provides attachment sites that enhance adhesion to host cells.	

ANS:	A
The outer cell wall of gram-negative bacteria acts as a barrier to hydrophobic compounds and harmful substances, acts as a sieve, and provides attachment sites that enhance adhesion to host cells. Flagella attach to the cell membrane, not to the cell wall.

OBJ:	Level 1: Recall	

	23.	Mycoplasma and Ureaplasma spp. must have media supplemented with serum or sugar as nutrients and because
a.	their cell walls contain only peptidoglycan.	
b.	they lack cell walls.	
c.	the sterols in their cell walls are soluble in normal bacterial media.	
d.	their cell walls contain detoxifying enzymes.	

ANS:	B
These two genera have no cell walls, so the other choices are not appropriate. Serum and sugar are needed nutrients and assist with osmotic balance of the media.

OBJ:	Level 1: Recall	

	24.	What is the purpose of a capsule?
a.	Prevent osmotic rupture of the cell membrane	
b.	Make up the periplasmic space	
c.	Act as a virulence factor in helping the pathogen evade phagocytosis	
d.	Provide an attachment site for somatic antigens	

ANS:	C
The capsule acts as a virulence factor in helping the pathogen evade phagocytosis because antibodies have difficulty attaching to the capsule of bacteria and therefore are unable to prepare the organism for ingestion. The cell membrane is not prone to osmotic rupture when inside a host; the periplasmic space is found between the peptidoglycan and the lipopolysaccharide layers of the cell wall in gram-negative organisms; and somatic antigens are found below the capsule.

OBJ:	Level 1: Recall	

	25.	The three basic shapes of bacteria include all the following, except
a.	spirochetes.	
b.	cell wall deficient.	
c.	cocci.	
d.	bacilli.	

ANS:	B
Cell wall deficient is not one of the basic shapes of bacteria. It refers to the cell wall composition, not the bacterial shape.

OBJ:	Level 1: Recall	

	26.	The Gram stain is a routine stain used in bacteriology to determine gram-positive and gram-negative bacteria based on the
a.	phenotypic characteristics of the organism.	
b.	composition of the bacterial cell wall.	
c.	composition of the bacterial cell membrane.	
d.	composition of the bacterial pili.	

ANS:	B
The composition of the bacterial cell wall is routinely used in bacteriology. The peptidoglycan cell walls of the gram-positive bacteria retain the crystal violet (purple) stain, whereas crystal violet stain is washed away because of the lipopolysaccharide (outer membrane) present in the cell walls of the gram-negative cells. The outer membrane retains the Safranin (pink) with the counter stain.

OBJ:	Level 1: Recall	

	27.	In what staining procedure does carbolfuchsin penetrate the bacterial cell wall through heat or detergent treatment?
a.	Gram stain	
b.	Acridine orange stain	
c.	Endospore stain	
d.	Acid-fast stain	

ANS:	D
Of all the stains listed, the acid-fast stain is the only one that requires heating or detergent treatment so that the carbolfuchsin stain can penetrate the waxy wall of acid-fast bacteria. Gram staining uses crystal violet stain; acridine orange is used in acridine orange stain; and the endospore stain uses malachite green.

OBJ:	Level 1: Recall	

	28.	What stain is used for medically important fungi?
a.	Methylene blue	
b.	Acridine orange	
c.	Acid-fast	
d.	Lactophenol cotton blue	

ANS:	D
Lactophenol cotton blue is the only fungi stain listed. Methylene blue is used to stain Corynebacterium spp.; acridine orange is used to stain all types of bacteria, living or dead; and acid-fast is used to stain Mycobacterium spp.

OBJ:	Level 1: Recall	

	29.	All the following are types of media, except
a.	selective.	
b.	differential.	
c.	fastidious.	
d.	transport.	

ANS:	C
Fastidious refers to the nutrient requirements of bacteria, not a type of media. Selective media have ingredients added to grow only selected bacteria. Differential media have chemicals added to allow visualization of metabolic differences of bacteria. Transport media are used to keep bacteria alive during transport to the laboratory.

OBJ:	Level 1: Recall	

	30.	Which of the following environmental factors influence the growth of bacteria in the laboratory?
a.	pH	
b.	Temperature	
c.	Gaseous composition of the atmosphere	
d.	All of the above	

ANS:	D
Most bacteria grow best at a pH between 7.0 and 7.5, at 35°C, with a requirement for the gaseous composition of the atmosphere. Some bacteria require higher than atmospheric moisture (humidity) levels for optimal growth (Neisseria sp.).

OBJ:	Level 1: Recall	

	31.	Some bacteria grow at 25°C or 42°C, but diagnostic laboratories routinely grow pathogenic bacteria at what temperature?
a.	30°C	
b.	60°C	
c.	35°C	
d.	10°C	

ANS:	C
Most pathogenic bacteria grow well at 35°C because it is close to body temperature; 30°C is the temperature at which most medically important fungi grow well; 60°C is too hot for pathogenic bacteria to grow, and 10°C is too cold for pathogenic bacteria to grow.

OBJ:	Level 1: Recall	

	32.	Which of these bacteria cannot grow in the presence of oxygen?
a.	Obligate aerobes	
b.	Capnophilic organisms	
c.	Facultative anaerobes	
d.	Obligate anaerobe	

ANS:	D
An obligate anaerobe is a bacterium that is killed when exposed to normal atmospheric conditions of oxygen and requires strict absence of oxygen. An obligate aerobe is a bacterium that grows only in the presence of oxygen, and a capnophilic bacterium grows only in the presence of 5% to 10% carbon dioxide.

OBJ:	Level 1: Recall	

	33.	What class of organisms, such as the Streptococcus sp., can survive in the presence of oxygen but do not use oxygen in its metabolic processes?
a.	Microaerophilic	
b.	Aerotolerant anaerobe	
c.	Obligate anaerobe	
d.	Facultative anaerobe	

ANS:	B
An aerotolerant anaerobe is one that can live in the presence of oxygen but does not use oxygen in its metabolic processes. A microaerophilic bacterium requires a reduced level of oxygen to grow. An obligate anaerobe cannot survive in the presence of oxygen, and a facultative anaerobe can grow either with or without oxygen.

OBJ:	Level 1: Recall	

	34.	The laboratory receives a specimen in which the doctor suspects that the infecting organism is Haemophilus influenzae. This organism grows best in an atmosphere that contains 5% to 10% carbon dioxide. It is therefore classified as what type of bacteria?
a.	Obligate aerobe	
b.	Capnophilic	
c.	Facultative anaerobe	
d.	Obligate anaerobe	

ANS:	B
Capnophilic bacteria need increased carbon dioxide in the atmosphere to grow; obligate aerobes can grow only in the presence of oxygen; facultative anaerobes can grow in the presence or absence of air; and obligate anaerobes need an atmosphere without oxygen to grow.

OBJ:	Level 1: Recall	

	35.	The following describes the log phase of bacterial growth:
a.	Preparing to divide	
b.	Limited nutrients with bacteria count remaining constant	
c.	Number of nonviable bacterial cells exceeds the number of viable cells	
d.	Bacteria doubling with each generation time	

ANS:	D
As a bacterium is immersed in an environment with favorable conditions for growth, the bacterium starts dividing; soon their numbers increase logarithmically. The growth tapers off as the nutrients become limited; then the bacteria will begin to die as the nutrients are exhausted.

OBJ:	Level 1: Recall	

	36.	Diagnostic schemes in the microbiology laboratory typically analyze each unknown bacterium’s metabolic processes for all the following, except
a.	utilization of a variety of substrates as carbon sources.	
b.	energy utilization for metabolic processes.	
c.	production of specific end products from specific substrates.	
d.	production of an acid or alkaline pH in the test medium.	

ANS:	B
The microbiologist examines production of specific end products, production of an acid or alkaline pH in the test medium, and utilization of various carbon sources for energy to identify bacteria. Identification schemes are based on the percentages of bacterial species that exhibit particular metabolic processes in vitro.

OBJ:	Level 1: Recall	

	37.	Which is a biochemical process carried out by both obligate and facultative anaerobes?
a.	Fermentation	
b.	Respiration	
c.	Oxidation	
d.	Reduction	

ANS:	A
Fermentation takes place without oxygen. Respiration and oxidation need oxygen to occur. Reduction is a chemical reaction that can occur independent of bacteria.

OBJ:	Level 1: Recall	

	38.	What type of fermentation produces lactic, acetic, succinic, and formic acids as the end products?
a.	Butanediol	
b.	Propionic	
c.	Mixed acid	
d.	Homolactic	

ANS:	C
Most of the fermentative processes produce only a single acid as a metabolic by-product. Mixed acid fermentation produces several different acids: lactic, acetic, succinic, and formic.

OBJ:	Level 1: Recall	

	39.	If bacteria utilize various carbohydrates for growth, they are usually detected by
a.	alkaline production and change of color from the pH indicator.	
b.	production of carbon dioxide.	
c.	production of keto acids.	
d.	acid production and change of color from the pH indicator.	

ANS:	D
Most bacterial identification systems examine the ability of bacteria to utilize several different carbohydrates. The medium contains the specific carbohydrate being examined and a pH indicator that can produce a color change: blue to yellow or red to yellow.

OBJ:	Level 1: Recall	

	40.	In the medical microbiology laboratory, the ability of a gram-negative bacterium to ferment this sugar is the first step in its identification.
a.	Sucrose	
b.	Mannitol	
c.	Trehalose	
d.	Lactose	

ANS:	D
Media used for gram-negative bacillus that contain this sugar allow for the differentiation into lactose fermenters and nonlactose fermenters. With this characteristic, organisms can be placed into these two large groupings. This aids in the identification of gram-negative organisms.

OBJ:	Level 1: Recall	

	41.	A _____ is a single, closed, circular piece of DNA that is supercoiled to fit inside a bacterial cell.
a.	phenotype	
b.	chromosome	
c.	frame-shift mutation	
d.	transposon	

ANS:	B
Chromosomes contain the genome of a bacterial cell. The DNA in the genome must be compacted and wrapped around protein molecules to fit inside the cell nucleus. This compacting, wrapping, and supercoiling makes up the chromosome.

OBJ:	Level 1: Recall	

	42.	Genes that code for antibiotic resistance are often found on small, circular pieces of DNA. These DNA pieces are called
a.	plasmids.	
b.	phenotypes.	
c.	chromosomes.	
d.	genomes.	

ANS:	A
Plasmids found in bacteria are small, extrachromosomal DNA. Plasmids are found in the cytoplasm and can be replicated and passed on to daughter cells. Plasmids contain the antibiotic resistance genes for some antibiotics.

OBJ:	Level 1: Recall	

	43.	What process involves transferring or exchanging genes between similar regions on two separate DNA molecules?
a.	IS element	
b.	Replication	
c.	Recombination	
d.	Transcription	

ANS:	C
Recombination is the process described. Transcription occurs when a DNA molecule makes an RNA molecule. Replication occurs when DNA is used to make another DNA molecule. An IS element is a type of mutation that occurs when a small piece of DNA jumps from one area in a chromosome to another.

OBJ:	Level 1: Recall	

	44.	A microbiologist is working with two separate cultures of the same organism. The bacteria in one culture are resistant to penicillin, whereas the bacteria in the other culture are susceptible to penicillin. The bacteria from both cultures are mixed together, and all the resulting bacteria are resistant to penicillin. What caused this phenomenon?
a.	The plasmid carrying the resistance gene was transferred to the susceptible population of bacteria.	
b.	The plasmid carrying the susceptibility gene was transferred to the resistant population of bacteria.	
c.	An IS element was inserted into the genome of the susceptible bacterial population.	
d.	A frame-shift mutation occurred that allowed the susceptible population of bacteria to develop resistance to penicillin.	

ANS:	A
Antibiotic resistance is carried by plasmids, which can easily be transferred from one bacterium to another. The receiving bacterium then displays the characteristics contained in the plasmid. IS elements and frame-shift mutations occur on the chromosomes and take longer to manifest than do plasmid transfers.

OBJ:	Level 2: Interpretation

	45.	Diphtheria is a disease produced by Corynebacterium diphtheriae. However, not all C. diphtheriae bacteria produce the toxin that causes this disease. To produce the toxin, the bacteria must first become infected with a bacteriophage. The process by which bacterial genes are transferred to new bacteria by the bacteriophage is called
a.	conjugation.	
b.	transduction.	
c.	replication.	
d.	transformation.	

ANS:	B
Conjugation occurs when genetic material is passed from one bacterium to another through the use of a sex pilus or similar appendages. Replication is when DNA makes a copy of itself. Transformation occurs when naked DNA or plasmids are taken up and incorporated into a bacteria’s genome.

OBJ:	Level 1: Recall	

	46.	Lysogeny occurs when
a.	genes present in the IS element are expressed in the bacterial cell.	
b.	genetic material is transferred from one bacterium to another through a sex pilus.	
c.	competent bacteria cells take up naked DNA.	
d.	genes present in the bacteriophage DNA are incorporated into the bacteria’s genome.	

ANS:	D
IS elements are small pieces of bacterial DNA that jumped from one area in a chromosome to another area in the same chromosome. When using a sex pilus to transfer DNA, the process is called conjugation. Competent cells taking up DNA into their genomes represent transduction.

OBJ:	Level 1: Recall	

	47.	These are enzymes that cut the bacterial DNA at specific locations.
a.	Bacteriophage enzymes	
b.	Restriction enzymes	
c.	Temperate lysogeny enzymes	
d.	Conjugation enzymes	

ANS:	B
Restriction enzymes allow bacteria to cut a place in its genome and insert specific sequences of foreign DNA. Researchers also use the resulting fragments to identify identical genomes. Bacteriophage enzymes do not cut the host bacteria DNA. Temperate lysogeny enzymes are associated with bacteriophage activation and conjugation enzymes assist in transfer of DNA from one bacterial cell to another.

OBJ:	Level 1: Recall