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Microorganisms MCQ's 2012

Question 1 of 40

1

Which of the following is a macronutrient?

Select one of the following:

  • Manganese

  • Magnesium

  • Zinc

  • Cobalt

Explanation

Question 2 of 40

1

Denitrification is a process by which:

Select one of the following:

  • Nitrogen gas is fixed by microorganisms

  • Nitrates are reduced to nitrogen gas

  • Nitrates are reduced to ammonia

  • Nitrogen is assimilated into cellular material

Explanation

Question 3 of 40

1

Carl Woese of the University of Illinois and his collaborators identified two major branches of prokaryotic evolution. What was the basis for dividing prokaryotes into two domains?

Select one of the following:

  • Microscopic examination of the staining characteristics of the cell wall

  • Metabolic characteristics such as the production of methane gas

  • Ecological characteristics such as the ability to survive extreme temperatures

  • Molecular characteristics such as ribosomal RNA sequences

Explanation

Question 4 of 40

1

Catalase is indispensable to:

Select one of the following:

  • Obligate anaerobes

  • Aerotolerant anaerobes

  • Aerobes

  • All of the above

Explanation

Question 5 of 40

1

Addition of blood to a culture medium allows haemolytic bacteria to be picked out. This is an example of a:

Select one of the following:

  • Selective medium

  • Differential medium

  • Synthetic medium

  • Defined medium

Explanation

Question 6 of 40

1

Which of these environmental factors influence microbial growth?

Select one of the following:

  • pH

  • Water potential

  • Oxygen

  • All of the above

Explanation

Question 7 of 40

1

Mutations are:

Select one of the following:

  • Chemical modifications of DNA or RNA molecules

  • Any changes of bacterial genome as compared with a wild type

  • Events resulting from genetic exchange between bacterial plasmids

  • Sequencing errors

Explanation

Question 8 of 40

1

A Wild-type bacterial strain is:

Select one of the following:

  • A strain with a limited number of mutations

  • An arbitrarily chosen strain

  • A strain without plasmids

  • A strain which is sensitive to antibiotics

Explanation

Question 9 of 40

1

Viruses may encode their genomes as:

Select one of the following:

  • DNA

  • RNA

  • negative strand RNA

  • All of the above

Explanation

Question 10 of 40

1

Virus particles:

Select one of the following:

  • Are always smaller than bacterial cells

  • Can replicate independently of a host cell if provided with a nutrient medium

  • Can use some of the enzymes expressed in the host cell to aid their replication

  • Are always eliminated by the host immune system

Explanation

Question 11 of 40

1

The symptom ‘chlorosis’ which develops when some fungi infect plants is due to:

Select one of the following:

  • Cell death

  • Nutrient imbalance

  • Impaired photosynthesis

  • Excess plant hormones

Explanation

Question 12 of 40

1

Which of the following is NOT a correct statement about true fungi:

Select one of the following:

  • True fungi are eukaryotic

  • All true fungi are multi-cellular

  • True fungi are heterotrophic

  • Most true fungi have chitin cell walls

Explanation

Question 13 of 40

1

The Bacille-Calmette-Guérin (BCG) vaccine is:

Select one of the following:

  • Heat-killed Mycobacterium tuberculosis

  • Attenuated live Mycobacterium tuberculosis

  • Mycobacterium bovis

  • Attenuated live Mycobacterium bovis

Explanation

Question 14 of 40

1

Which of the following is transmitted to humans by arthropods?

Select one of the following:

  • Tuberculosis

  • Malaria

  • Cholera

  • Typhoid

Explanation

Question 15 of 40

1

Pasteur is attributed with which one of the following discoveries?

Select one of the following:

  • Was the first to see microorganisms under a microscope

  • First to discover and use agar

  • That there could be life without air

  • The first chemical antibiotics

Explanation

Question 16 of 40

1

The length of a typical E. coli cell is approximately?

Select one of the following:

  • 20 μm

  • 2 μm

  • 200 nm

  • 20 nm

Explanation

Question 17 of 40

1

With respect to differences between members of the archaeal and bacterial domains/kingdoms, which is the CORRECT statement?

Select one of the following:

  • Both have peptidoglycan in their cell walls

  • Only some Archaea are capable of methanogenesis

  • Archaea are sensitive to β-lactam antibiotics

  • Bacteria have similar RNA polymerase to that of Archaea

Explanation

Question 18 of 40

1

Which statement is correct with respect to the E. coli chromosome?

Select one of the following:

  • It is negatively supercoiled

  • It is positively supercoiled

  • There are typically several origins of replication

  • It consists of over 50 million base pairs

Explanation

Question 19 of 40

1

A culture of E. coli is diluted by a factor of x 10-5 and, after plating out 100 μl on an agar plate, 78 colonies grew after incubation at 37oC overnight. The original culture therefore contained how many viable E. coli cells per ml?

Select one of the following:

  • 7.8 x 10(7)

  • 7.8 x 10(8)

  • 7.8 x 10(6)

  • 7.8 x 10(5)

Explanation

Question 20 of 40

1

Bacterial flagella bring about cell motion by which mechanism?

Select one of the following:

  • Wave-like movement of the flagellum

  • Rotation of the cell

  • Rotation of the flagellum in one direction only

  • Rotation of the flagellum that is reversible

Explanation

Question 21 of 40

1

Incorporation of atmospheric N2 to NH4+ occurs via the process of:

Select one of the following:

  • Nitrogen fixation

  • Nitrification

  • Denitrification

  • None of the above, atmospheric N2 cannot be incorporated into NH4+.

Explanation

Question 22 of 40

1

Active transport is necessary when:

Select one of the following:

  • Diffusion will not allow adequate amounts of a substance to enter the cell

  • Movement into the cell is against a concentration gradient

  • The level of nutrients in nature is very low

  • All of the above

Explanation

Question 23 of 40

1

The size of the most useful RNA molecule for prokaryotic evolutionary studies is:

Select one of the following:

  • 5S

  • 16S

  • 18S

  • 23S

Explanation

Question 24 of 40

1

Siderophores:

Select one of the following:

  • Act as a solvent for iron and transport iron into the cells

  • Are a key component of cytochromes

  • Help maintain osmotic balance in seawater microbes

  • Develop when errors in membrane synthesis occur

Explanation

Question 25 of 40

1

Chemical energy is released when organic or inorganic compounds are:

Select one of the following:

  • Reduced

  • Incorporated into larger molecules

  • Synthesized

  • Oxidized

Explanation

Question 26 of 40

1

MacConkey agar selects for:

Select one of the following:

  • Gram-negative enteric bacteria

  • Gram-positive bacteria

  • Both Gram-positive and Gram-negative bacteria

  • Haemolytic microorganisms

Explanation

Question 27 of 40

1

The Bacterial chromosome is:

Select one of the following:

  • Circular DNA

  • Linear DNA

  • Either circular or linear DNA

  • Double stranded RNA

Explanation

Question 28 of 40

1

With regards to bacterial plasmids which statement is the CORRECT one?

Select one of the following:

  • Plasmids are extra chromosomal DNA that encode only resistance to antibiotics

  • Plasmids are a part of the bacterial chromosome

  • Plasmids are single stranded DNA found in some bacteria

  • Plasmids are extra chromosomal DNA molecules

Explanation

Question 29 of 40

1

Which is the TRUE statement below:

Select one of the following:

  • Viruses do not infect microorganisms

  • All viruses are enveloped

  • All viruses cause disease

  • All viruses are parasites

Explanation

Question 30 of 40

1

The poliovirus mature virus particle:

Select one of the following:

  • Contains 240 copies of a single protein

  • Contains 60 copies of four proteins

  • Has a dsDNA genome

  • Has a single stranded negative–sense genome

Explanation

Question 31 of 40

1

Phytophthora infestans is a fungus-like organism which:

Select one of the following:

  • Causes disease of a wide range of woody hosts

  • Causes potato blight

  • Causes ringworm

  • Causes black sigatoka disease of banana

Explanation

Question 32 of 40

1

Zoophilic dermatophytes are:

Select one of the following:

  • normally associated with animals and humans

  • normally only associated with humans

  • mainly associated with the soil

  • mainly associated with contaminated water

Explanation

Question 33 of 40

1

Which of the following is primarily a respiratory pathogen?

Select one of the following:

  • Vibrio cholerae

  • Mycobacterium tuberculosis

  • Salmonella typhi

  • Mycobacterium leprae

Explanation

Question 34 of 40

1

Which of the following is NOT an acquired mechanism of antibiotic resistance in bacteria?

Select one of the following:

  • Beta-lactamase production

  • Efflux pump antibiotic export

  • Lack of peptidoglycan

  • RNA polymerase single nucleotide change

Explanation

Question 35 of 40

1

With regard to the differences between bacterial and eukaryotic cells which statement is the CORRECT one?

Select one of the following:

  • Bacterial cells contain mitochondria

  • Bacterial cells are usually larger than eukaryote cells

  • Bacteria do not contain a chromosome

  • Only bacterial cells are sensitive to β-lactam antibiotics

Explanation

Question 36 of 40

1

Koch’s postulates most correctly relate to which one of the following statements?

Select one of the following:

  • The isolation of a bacterium in culture from a human alone indicates that it causes disease

  • Determination in a series of logical steps the agent that causes disease

  • The observation of bacterial cells in tissue from a human with disease indicates that the observed bacterium has caused the disease

  • Inoculation of a bacterium into an animal to cause disease alone indicates that it is the cause of the disease observed

Explanation

Question 37 of 40

1

Which statement is CORRECT with respect to Lipopolysaccharide (LPS)?

Select one of the following:

  • LPS is found in Gram positive cells

  • LPS is found in Gram negative cells in the cytoplasmic membrane

  • LPS is found in the outer-membrane of Gram negative cells.

  • LPS is found inside all bacterial cells

Explanation

Question 38 of 40

1

A culture of E. coli is diluted by a factor of 10-6 and, after plating out 100 μl on an agar plate, 94 colonies grew after incubation at 37oC overnight. The original culture therefore contained how many viable E. coli cells per ml?

Select one of the following:

  • 9.4 x 10(7)

  • 9.4 x 10(8)

  • 9.4 x 10(6)

  • 9.4 x 10(5)

Explanation

Question 39 of 40

1

With respect to differences between members of the archaeal and bacterial domains/kingdoms, which is the CORRECT statement?

Select one of the following:

  • Both have peptidoglycan in their cell walls

  • Only some Archaea are capable of methanogenesis

  • Archaea are sensitive to β-lactam antibiotics

  • Bacteria have similar RNA polymerase to that of Archaea

Explanation

Question 40 of 40

1

Which statement is CORRECT with respect to peptidoglycan?

Select one of the following:

  • There are multiple molecules of peptidoglycan in bacterial cell walls

  • Only Gram positive cells possess peptidoglycan

  • There is only a single molecule of peptidoglycan in a bacterial cell wall

  • Peptidoglycan is only found in the Gram negative cell wall

Explanation

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