Microbial Growth I
In which environment are you most likely to encounter an acidophile?
A) human blood at pH 7.2
B) milk at pH 6.5
C) human intestine at pH 8.5
D) a hot vent at pH 1.5
D) a hot vent at pH 1.5
The phase of the bacterial growth curve in which the rate of multiplication equals the rate of cell death is the:
A) lag phase.
B) log phase.
C) stationary phase.
D) death phase.
C) stationary phase.
Which of the following is suitable for use on tissues for microbial control to prevent infection?
A) disinfectant
B) antiseptic
C) sterilant
D) water
B) antiseptic
Which concentration of ethanol is the most effective bactericide?
A) 100 percent
B) 70 percent
C) 50 percent
D) 40 percent
B) 70 percent
More than half of the available antibiotics are:
A) Produced by fungi
B) Produced by bacteria
C) Synthesized in laboratories
D) Produced by Fleming
B) Produced by bacteria
A soup container was forgotten in the refrigerator and shows contamination. The contaminants are probably which of the following?
A) thermophiles
B) psychrophile
C) psychrotrophs
D) mesophiles
C) psychrotrophs
An inoculated thioglycolate medium culture tube shows dense growth at the surface and turbidity throughout the rest of the tube. What is your conclusion?
A) The organisms die in the presence of oxygen
B) The organisms are facultative anaerobes.
C) The organisms are microaerophiles.
D) The organisms are obligate aerobes.
B) The organisms are facultative anaerobes.
Cleansing technique that mechanically removes microorganisms to reduce contamination to a safe level is called:
A) sterilization
B) pasteurization
C) sanitization
D) degermation
C) sanitization
Which of the following treatments is the most effective for controlling microbial growth?
A) 63°C for 30 minutes
B) 72°C for 15 seconds
C) 140°C for 4 seconds
D) They are equivalent treatments.
D) They are equivalent treatments.
Penicillin, cephalosporins, and carbapenems share a common structural feature that is critical for their antibacterial activity. Which of the following best describes this shared characteristic?
A) β-lactam ring
B) A long hydrophobic tail
C) A positively charged domain
D) A nucleoside-like structure
A) β-lactam ring
Bacteria living in salt marshes are most likely which of the following?
A) acidophiles
B) alkaliphile
C) halotolerant
D) thermophiles
C) halotolerant
The E. coli that normally live in the human large intestines and produce vitamin K for the body to use would best be termed a _____ relationship.
A) parasitic
B) saprobic
C) commensal
D) mutualistic
D) mutualistic
Which of the following does NOT achieve sterilization?
A) Dry heat
B) Pasteurization
C) Autoclave
D) Ethylene oxide
B) Pasteurization
Phenol and Phenolics exert their antimicrobial action by:
A) inhibiting the cell wall synthesis
B) blocking protein synthesis
C) injuring the plasma membrane
D) denaturing proteins
C) injuring the plasma membrane
Penicillin and its derivatives inhibit bacterial growth by targeting transpeptidase enzymes, known as penicillin-binding proteins (PBPs). What is the direct consequence of this inhibition?
A) Ribosomal protein synthesis is blocked due to the failure of peptide bond formation
B) Peptidoglycan cross-linking is prevented, weakening the bacterial cell wall
C) DNA replication is halted by the inhibition of DNA gyrase
D) Cytoplasmic membrane integrity is disrupted, leading to cell lysis
B) Peptidoglycan cross-linking is prevented, weakening the bacterial cell wall
In which environment are you most likely to encounter a hyperthermophile?
A) hot tub
B) warm ocean water in Florida
C) human body
D) hydrothermal vent at the bottom of the ocean
D) hydrothermal vent at the bottom of the ocean
When microbes live independently but cooperate and share nutrients, it is called:
A) synergism.
B) commensalism.
C) mutualism.
D) symbiosis.
A) synergism.
Which of the following microbial control methods does not actually kill microbes or inhibit their growth but instead removes them PHYSICALLY from samples?
A) filtration
B) pasteurization
C) lyophilization
D) nonionizing radiation
A) filtration
Which of the following chemical agents is used for sterilization?
A) Ethylene oxide
B) Phenolics
C) Alcohol
D) Chlorine
A) Ethylene oxide
The antibiotic tetracycline binds to the 30S subunit of the ribosome, interfering with the attachment of the tRNA to the mRNA-ribosome complex. Why is tetracycline selectively toxic against bacteria?
A) Eukaryotic cells will enzymatically destroy the drug.
B) Eukaryotic cells will actively pump the drug out of their interiors.
C) The drug binds to the 30S small ribosomal subunit–eukaryotes have a 40S small subunit.
D) Eukaryotes lack a small ribosomal subunit, so the drug cannot negatively affect them
C) The drug binds to the 30S small ribosomal subunit–eukaryotes have a 40S small subunit.
A microorganism that does not have catalase or superoxide dismutase would find it difficult to live in an environment with:
A) carbon dioxide.
B) oxygen.
C) high salt.
D) temperatures above 37 °C.
B) oxygen.
Quorum sensing is used by bacterial cells to communicate, and it is determined by which of the following?
A) the size of the population
B) the availability of nutrients
C) the speed of water flow
D) the density of the population
D) the density of the population
The decimal reduction time refers to the amount of time it takes to do which of the following?
A) reduce a microbial population by 10%
B) reduce a microbial population by 0.1%
C) reduce a microbial population by 90%
D) completely eliminate a microbial population
C) reduce a microbial population by 90%
Which type of test is used to determine a chemical’s disinfection effectiveness on an inanimate surface?
A) disk-diffusion assay
B) phenol coefficient test
C) in-use test
D) use-dilution test
D) use-dilution test
Which of the following resistance mechanisms describes the function of b-lactamase?
A) Efflux pump
B) Target mimicry
C) Drug inactivation
D) Target overproduction
C) Drug inactivation