Chapter 6 - Microbial Growth

A microorganism grows in the lab on medium containing mineral salts but no organic compounds. The organism is likely to be a(n) A) heterotroph. B) autotroph. C) chemotroph. D) chemoheterotroph. E) The answer cannot be determined from the information provided.

A cell that uses an organic carbon source and obtains energy from light would be called a A) photoheterotroph. B) lithoautotroph. C) photoautotroph. D) chemoheterotroph. E) chemoautotroph.

A(n) __________ organism is one that requires oxygen for growth. A) anaerobic B) facultative anaerobic C) aerotolerant D) obligate aerobic E) both aerotolerant and anaerobic

An aquatic microbe that can grow only at the surface of the water is probably which of the following? A) a phototroph B) a heterotroph C) a chemotroph D) a lithotroph E) an anaerobe

An organism that produces catalase enzyme is protected from the harmful effects of A) singlet oxygen. B) peroxide anion. C) superoxide radical. D) hydroxyl radical. E) molecular oxygen.

What is used to protect organisms from the toxic by-products of oxygen?

A microbe that grows only at the bottom of a tube of thioglycollate medium is probably a(n) A) obligate aerobe. B) facultative anaerobe. C) aerotolerant anaerobe. D) microaerophile. E) obligate anaerobe.

Nitrogen is a growth limiting nutrient for many organisms because A) it is necessary for the biosynthesis of amino acids. B) it is required for synthesis of nucleotides. C) it is required for lipid synthesis. D) only a small number of bacteria are able to extract it from the atmosphere. E) only a few microbes can extract it from the atmosphere, but all organisms require it for amino acid and nucleotide synthesis.

At temperatures higher than the maximum growth temperature for an organism, A) proteins are permanently denatured. B) membranes become too fluid for proper function. C) hydrogen bonds within molecules are broken. D) hydrogen bonds are broken, and proteins are permanently denatured. E) hydrogen bonds are broken, proteins are denatured, and membranes become too fluid.

An organism that requires chemical nutrients which serve as final electron acceptors is an A) chemotroph. B) aerobe C) phototroph. D) lithotroph. E) autotroph.

Human pathogens are classified as A) thermophiles. B) thermoduric. C) hyperthermophiles. D) mesophiles. E) psychrophiles.

In the process of _____ microbes detect the presence and density of other microbes and modify their metabolic activity in response. A) mutualism B) quorum sensing C) synergy D) symbiosis E) antagonism

Which of the following organisms would be most likely to contaminate a jar of pickles? A) a neutrophile B) a thermophile C) an acidophile D) an obligate anaerobe E) a mesophile

Organisms that can grow with or without oxygen present are A) obligate aerobes. B) facultative anaerobes. C) either facultative anaerobes or aerotolerant anaerobes. D) obligate anaerobes. E) aerotolerant anaerobes.

A fastidious organism might be grown on which of the following types of media? A) transport media B) reducing media C) enriched media D) differential media E) selective media

Obligate anaerobes may be cultured in the laboratory A) in a reducing medium. B) in a candle jar. C) in standard Petri plates. D) on blood agar plates. E) on blood agar plates in a candle jar.

Joan wants to discover a microbe capable of degrading an environmental contaminant. Which culturing method would be most effective for isolation of such an organism? A) cell culture B) chemostat C) quorum sensing D) enrichment culture E) nitrogen fixation

A microbiologist inoculates a growth medium with 100 bacterial cells/ml. If the generation time of the species is 1 hour, and there is no lag phase, how long will it be before the culture contains more than 10,000 cells/ml? A) 24 hours B) 7 hours C) 2 hours D) 3 hours E) 10 hours

An epidemiologist is investigating a new disease and observes what appear to be bacteria inside tissue cells in clinical samples from victims. The scientist wants to try to isolate the bacteria in the lab. What culture conditions are most likely to be successful? A) culturing on blood agar plates B) inoculation of EMB plates C) incubation in a candle jar D) inoculation of cell cultures E) inoculation of a minimal medium broth

The events of binary fission are

MacConkey agar plates represent __________ medium. A) a minimal B) a selective C) a differential D) both a differential and a selective E) both a minimal and a selective

Which method provides information about the number of living cells in a sample of bacterial culture?

The growth of bacterial cultures is best described as A) arithmetic growth. B) lag growth. C) logarithmic growth. D) cell division. E) replication.

A ________ is used in industrial microbiology to produce microbial products that are only synthesized during log phase growth. A) Coulter counter B) broth culture C) spectrophotometer D) pour plate E) chemostat

The ________ of a population is the time it takes for the cells to double in number. A) binary fission B) exponential growth C) generation time D) arithmetic growth E) log phase

Which of the following is an indirect method for estimating the number of microbes in a sample? A) viable plate counts B) turbidity C) Coulter counter D) MPN E) membrane filtration

During which growth phase are bacteria more susceptible to antimicrobial drugs? A) lag phase B) log phase C) stationary phase D) death phase E) The susceptibility is the same for all phases.

The use of salt and sugar in preserving various types of foods is an application of which of the following concepts? A) nitrogen fixation B) osmotic pressure C) pH D) hydrostatic pressure E) quorum sensing

A clinical sample labeled as "sputum" was collected from A) the skin. B) the blood. C) the central nervous system. D) a piece of tissue. E) the lungs.

The method of obtaining isolated cultures that utilizes surface area to physically dilute specimens is called A) Coulter-counter B) viable plate-count C) streak-plate D) turbidity E) direct microscopic-count

______ are complex communities of various types of microbes that adhere to surfaces. A) Aggregates B) Colonies C) Isolates D) Biofilms E) Media

The ________ method provides an estimate of the CFUs (colony forming units) in a sample. A) Coulter-counter B) viable plate-count C) streak-plate D) turbidity E) direct microscopic-count

Blood agar plates are an example of ________ medium. A) differential B) selective C) reducing D) defined E) transport

What types of media of commonly used to isolate anaerobic microbes?

The Most Probable Number (MPN) method is used A) to estimate numbers of cells in samples with a high density of bacterial cells. B) when samples contain obligate anaerobes. C) to estimate numbers of cells in samples with a low density of bacterial cells. D) to isolate autotrophic bacteria. E) to determine the generation time of bacterial isolates.

*Refer to graph on page 3 of chapter 6 study guide. The correct sequence for the phases indicated by the letters A,B,C and D is

The generation time of bacterial cells is shortest during the ________ phase. A) death B) lag C) log D) stationary E) longitudinal

When cells are metabolically active but not dividing, they are in the ________ phase. A) stationary B) log C) lag D) death E) exponential

Rates of cell production and cell death are approximately equal during the ________ phase of growth. A) lag B) log C) death D) stationary E) intermediate

Creating conditions in the laboratory that promote the growth of some microbes while inhibiting the growth of others is called A) reducing conditions. B) differential culturing. C) complex culturing. D) selective enrichment culturing. E) transport conditions.

A laboratory recipe lists sucrose, an ammonia compound, calcium salts and a buffer as the ingredients for a microbiologic medium. These are added to water and autoclaved. What type of medium does this protocol produce? A) defined agar B) defined broth C) complex broth D) reducing agar E) complex enrichment broth

A capnophile is a microorganism that thrives in conditions of high A) carbon dioxide levels. B) hydrostatic pressure. C) oxygen levels. D) pH. E) salt concentration.

A microorganism found living under conditions of high ________ is a barophile. A) pH values B) oxygen concentrations C) hydrostatic pressure D) carbon dioxide levels E) salt concentrations

Microaerophiles are microbes that grow best at low A) carbon dioxide levels. B) pH values. C) hydrostatic pressure. D) oxygen levels. E) salt concentrations.

A 0.1 ml sample of a log phase culture contains 10,000 bacterial cells/ml. It is added to 9.9 ml of fresh culture medium broth. Assume a generation time of 30 minutes, and no limiting nutrients. How many bacteria will be present in the entire broth culture after five hours? A) 3.2 × 104 B) 5.0 × 105 C) 1.02 × 106 D) 6.0 × 106 E) 2.56 × 107

Obligate anaerobes have enzymes such as superoxide dismutase to protect them from the damaging effects of oxygen. T of F?

Nitrogen fixation is a process that occurs in all bacteria. T or F?

Thermoduric mesophiles are often responsible for spoilage of improperly canned foods. T or F?

Serial dilution can be used in combination with pour plates as a method for isolating pure cultures. T/F

The only effective way to store bacterial cultures for short periods of time is to arrest their metabolism by freezing. T or F?

Quorum sensing is involved in the development and propagation of a biofilm. T or F?

Differential media are not useful for isolation of microbes. T or F?

Agar is a useful compound in the microbiology lab because it is an excellent nutrient for bacteria. T or F?

Enrichment culturing may require use of controlled environmental conditions. T or F?

Flow cytometry makes use of fluorescence to count microbes. T or F?

A(n) (autotroph/lithotroph/organotroph) uses inorganic molecules as electron donors.

Organisms that require organic sources of carbon and energy are called (chemoheterotrophs/chemoautotrophs/auxotrophs).

The (peroxide/superoxide/hydroxyl) radical is formed during the incomplete reduction of O2 during electron transport in aerobes.

The (optimum/range/minimum) growth temperature is the temperature at which an organism exhibits the highest growth rate.

The preferred method for long term storage of bacteria is (freezing/refrigeration/lyophilization).

Alkalinophiles can survive in water up to pH (11.5/10/7.0).

Some organisms use vitamins as (oxidizers/antioxidants/peroxidases) to be able to live as aerobes.

A(n) (culture/specimen/inoculum) is a sample of microorganisms introduced into a growth medium.

A pure culture is composed of cells that arise from a single (cell/inoculum/sample).

Culturing of intracellular parasites generally requires (enrichment/cell culture/low oxygen) conditions.

A sample placed into fresh medium is initially in the (lag/log/stationary) phase of microbial growth in most instances.

A growth curve plots the (number/concentration) of viable organisms in a growing population over time.

A (Coulter/Petroff-Hauser chamber/spectrophotometer) counter is used to count cells on a light microscope.

A clinical sample from a mucus membrane is usually collected as a (biopsy/needle/swab) specimen.

A (Coulter counter/cytometer/spectrophotometer) can measure changes in the turbidity of a bacterial culture.