1. Which of the following is the nutritional characterization of Escherichia coli?
a) Chemotrophic
b) Organotrophic
c) Autotrophic
d) Chemotrophic, Organotrophic, Heterotrophic
Explanation: Escherichia coli are chemotrophic, organotrophic, and heterotrophic organisms. This means they rely on chemical compounds for their energy and uses organic compounds as electron donors. They also require organic compounds as their carbon source and are hence heterotrophic.
2. Which of the following amino acids require sulphur for their synthesis?
a) tryptophan
b) methionine
c) cystine
d) methionine and cystine
Explanation: Sulphur is needed for synthesis of certain amino acids like methionine and cystine. Some bacteria require organic sulphur compounds, some are capable of utilizing inorganic sulphur compounds and some can even use elemental sulphur.
3. Phosphorus is essential component of __________
a) teichoic acid
b) nucleotides
c) phospholipids
d) teichoic acid, nucleotides, phospholipids
Explanation: Phosphorus, usually supplied in the form of phosphate, is an essential component of nucleotides, nucleic acids, phospholipids, teichoic acids, and other components.
4. Which of the following are trace elements?
a) Potassium ion
b) Sodium ion
c) Copper ion
d) Magnesium ion
Explanation: Trace elements are those elements that are needed at very low concentrations such as Zinc ion, Copper ion, Manganese ion, Nickel ion, Cobalt ion, Boron ion, Molybdenum ion. They always occur as contaminants of other components of culture media in amounts sufficient to support bacterial growth.
5. Which of the following ions are cofactors for various enzymes?
a) Potassium ion
b) Iron ion
c) Magnesium ion and Iron ion
d) Calcium ion
Explanation: Among the trace elements, iron ion, magnesium ion, zinc ion, manganese ion and copper ion are known to be cofactors for various enzymes.
6. ”Red extreme halophiles”, are members of the archaebacterial which cannot grow with less than 12 to 15 percent NaCl.
a) True
b) False
Explanation: Most bacteria do not require Na ion, but certain marine bacteria, cyanobacteria and photosynthetic bacteria do require it. For those members of the archaeobacteria known as the “red extreme halophiles”, the requirement is astonishing: they cannot grow with less than 12 to 15 percent NaCl. They require this high level of NaCl for maintenance of the integrity of their cell walls and for the stability and activity of certain of their enzymes.
7. Which of the following are functions of water in the culture medium?
a) nutrients must be in aqueous solution
b) cofactor of enzymes
c) provides resistance to sudden transient temperature changes
d) it is a chemical reactant, nutrients must also be present in aqueous solution and provide resistance to sudden temperature changes
Explanation: In the case of bacteria, all nutrients must be in aqueous solution before they can enter the cells. The high specific heat of water provides resistance to sudden, transient temperature changes in the environment. Water is also a chemical reactant, being required for the many hydrolytic reactions carried out by a cell.
8. Chromatium okenii uses which of the following compound as electron donor?
a) Hydrogen sulphide
b) Fatty acids
c) Alcohol
d) Succinate
Explanation: Chromatium okenii are photolithotrophs i.e., they are phototrophic bacteria that uses inorganic compounds as their source of electrons. They use Hydrogen Sulphide as its electron donor, oxidizing it to elemental sulphur.
9. Which of the following bacteria can grow both as chemolithotrophs or as chemoorganotrophs?
a) Nitrosomonas sp.
b) Pseudomonas pseudoflava
c) Rhodospirillum rubrum
d) Chromatium okenii
Explanation: Pseudomonas pseudoflava can grow either as chemolithotrophs or chemoorganotrophs. They can use either the organic compound glucose or the inorganic compound hydrogen as its source of electrons.
10. Which of the following is a characteristic of beef extract?
a) product resulting from the digestion of proteinaceous materials
b) aqueous extract of lean beef tissue
c) aqueous extract of yeast cells
d) complex carbohydrate obtained from certain marine algae
Explanation: Beef extract, a complex raw material used as ingredient for preparing bacteriological media is an aqueous extract of lean beef tissue concentrated to a paste.