MULTIPLE CHOICE QUESTIONS FOR M.SC. MICROBIOLOGY ENTRANCE EXAM PREPARATION, TU, 2012 (SUBJECT: INSTRUMENTATION & BIOCHEMISTRY)

MULTIPLE CHOICE QUESTIONS : INSTRUMENTATION and BIOCHEMISTRY

1.        Percent (%) solution of any compound is prepared by

a.        w/w

b.        w/v

c.        v/v

d.        All

2.        One gram  equivalent weight per liter of solution is known as

a.        1 M solution

b.        1 N solution

c.        Concentrated solution

d.        Saturated solution

3.        95 % pure HCl with sp. Gravity=1,080 g/L has how many molar HCl?

a.        29.6 M

b.        28.11 M

c.        25 M

d.        6 M

4.        1 ppm (parts per million) is equivalent to

a.        1 mg/L

b.        1 g/L

c.        1 mg/100 mL

d.        1 mg/L

5.        Which of the following solutions are equal in concentration?

a.        1 N HCl & 1 M H₂SO₄

b.        2 N HCl & 1N HNO₃

c.        2 N HCl & 1 M H₂SO₄

d.        All

6.        50 ml 0.2 M of KH₂PO₄ is mixed with 50 ml of K₂HPO₄ to make final volume 200 ml, what is the final molarity of the mixture?

a.        0.2 M

b.        0.1 M

c.        0.4 M

d.        None

7.        Phosphate buffer has ………………. pKa values

a.        1

b.        2

c.        3

d.        4

8.        What are the components of Acetate buffer?

a.        CH₃COOH & CH₃COONa

b.        CH₃COOH & H₂O

c.        CH₃COONa & H₂O

d.        CH₃COONa & HCOOH

9.        The pKa value of acetate buffer is

a.        1.25

b.        7.60

c.        4.76

d.        9.25

10.     The pH adjustment of phosphate buffer can’t be done by

a.        1 N HCl

b.        1 N H₃PO₄

c.        1 NaOH

d.        None

11.     Buffer used for DNA preparation is

a.        Carbonate buffer

b.        Phosphate buffer

c.        Citrate buffer

d.        Tris buffer

12.     Which one cell is the strongest cell against mechanical cell disruption?

a.        Gm + cell

b.        Gm – cell

c.        Yeast cell

d.        Plant cell

13.     Extraction of which biomolecule don’t need cell disintegration?

a.        DNA

b.        Ribozyme

c.        Integral protein

d.        Antibiotics

14.     The clearance space of Dounce’s homogenizer ranges from

a.        0.1 mm – 0.6 mm

b.        1 mm – 6 mm

c.        0.001 mm – 0.006 mm

d.        1 nm -  6 nm

15.     The ultrasonic vibrations have frequency of

a.        Below 20 Hz

b.        Above 20 KHz

c.        Equivalent to 10,000 Hz

d.        Above 50 MHz

16.     Lysozyme breaks down the bond in cell wall.

a.        a 1-4 glycosidic bond in between NAG and NAM

b.        a 1-4 glycosidic bond in between NAM and NAG

c.        b 1-4 glycosidic bond in between NAG and NAM

d.        b 1-4 glycosidic bond in between NAM and NAG

17.     Protein precipitation by salting out can be best obtained by

a.        NaCl

b.        NH₄Cl

c.        (NH4)₂SO₄

d.        Na-citrate

18.     The saturated solution of NaCl is used to precipitate

a.        Albumin only

b.        Globulin only

c.        Both

d.        None

19.     The ionic strength of 1 N (NH4)₂SO₄ is equivalent to

a.        1

b.        2

c.        3

d.        4

20.     The most effective anion in salting out is

a.        SO₄^¯¯

b.        PO₄^¯¯¯

c.        Cl¯

d.        NO₃¯

21.     At isoelectric point, a protein has its

a.        Maximal solubility

b.        Minimum solubility

c.        Maximum charge

d.        Minimum activity

22.     Denaturation of proteins leads to loss of biological activity by

a.        Formation of amino acid

b.        Loss of primary structure

c.        Loss of both primary and secondary structure

d.        Loss of secondary and tertiary structure

23.     Which one of the following is not a protein determination method?

a.        Biuret method

b.        Barfoed method

c.        Lowry method

d.        Bicinchonic acid method

24.     The purity of an enzyme at various stages of purification is best measured by:

a.        Total protein

b.        Total enzyme activity

c.        Specific activity of the enzyme

d.        Percent recovery of protein

25.     The sensitivity of CBB G250 Dye binding method is

a.        > 1 mg

b.        > 1 mg

c.        > 1 Ng

d.        > 1 g

26.     The quantization of DNA and protein by UV method is done at

a.        265 nm & 300 nm

b.        450 nm & 595 nm

c.        260 nm and 280 nm

d.        190 nm & 260 nm

27.     The absorbance in Lowry method is measured at

a.        595 nm

b.        660 nm

c.        280 nm

d.        450 nm

28.     Proteins absorbs maximally UV radiation due to the presence of

a.        Tryptophan

b.        Tyrosine

c.        Phenyl alanine

d.        All of the above

Antibiotic Susceptibility test and Minimum Inhibitory Concentration tests

A. DISC DIFFUSION METHOD FOR THE ANTIMICROBIAL SUSCEPTIBILITY TESTING

principle:

A standardized inoculum of bacteria is swabbed onto the surface of a Mueller Hinton agar (MHA) plate. Filter paper disc impregnated with antimicrobial agents are placed on the agar. After overnight incubation, the diameter of the zone of inhibition is measured around each disc. By referring to the tables in the CLSI disc diffusion standard, a qualitative report of susceptible, intermediate or resistant is obtained.

Quality control:

      A. QC strains

     1.  Escherichia coli ATCC 25922     2. Staphylococcus aureus ATCC 25923

     3. Enterococcus faecalis ATCC 29212           

B. Monitoring accuracy

      1. Test QC strains by following routine procedure, and record results. Record lot number and expiration date of discs and agar.

      2. Compare to expected results (CLSI QC tables). Note any out of control result and document; proceed with corrective action, if necessary.

      3. Perform daily and weekly QC testing.

PROCEDURE:

1. Brings agar plates and canisters of discs to room temperature before use. Agar plates may be removed from refrigerator and placed in a 35 C ambient air incubator with lids slightly ajar to evaporate excess moisture. Do not leave in incubator for longer than 30 min.
2. Inoculum preparation

Using a loop or swab, transfer colonies as follows

1. Direct colony suspension method: - pick several colonies from a fresh (18 – 24 hr) nonselective agar plate to broth or 0.9% NaCl.
2. log phase method

a.       Pick four or five isolated colonies to 3.0 to 5.0 ml of broth.

b.      Incubate at 35 C for 2 to 8 hr until growth reaches the turbidity at or above that of a 0.5 McFarland standards.

3. For either the log phase or direct colony suspension method, vortex well and adjust turbidity visually with sterile broth or 0.9% NaCl to match a 0.5% McFarland standard.
2. Inoculation of agar plates
1. Within 15 minutes of adjusting turbidity, dip a sterile cotton swab into the inoculum and rotate against the wall of the tube above the liquid to remove excess inoculum.
2. Swab entire surface of agar plate three times, rotating plates approximately 60˚ between streaking to ensure even distribution. Avoid hitting the slides of the plate to avoid aerosols. Finally, run swab around the edge of the agar to remove any excess moisture.
3. Allow inoculated plate to stand for 3 to 15 min before applying discs.
3. Application of discs
1. Apply disc to agar surface with dispenser or manually with a sterile forceps.
2. Apply gentle pressure with sterile forceps or needle to ensure complete contact of disc with agar.
3. Do not place discs closer than 24mm from center to center (no more than 12 discs on 150 mm plates and 5 discs on 100 mm plates.
4. Do not relocate a disc once it has made contact with agar surface. Instead, place a new disc in another location on the agar.
4. Incubation
1. Invert plates and incubate within 15 min of disc application.           
2. Incubate for 16 to 18 at 35˚C in an ambient air incubator.
5. Reading plates
1. Read plates only if lawn of growth is confluent or nearly confluent.
2. Hold inverted plate a few inches above a black nonreflecting surface.
3. Illuminate plate with reflected light.
4. Use a sliding caliper or ruler held on the back of the plate to measure the diameter of inhibition zone to nearest whole millimeter.
5. When measuring zones for sulfonamides, trimethoprim, or trimethoprim- sulfamethoxazole, disregard light growth (20% less of lawn of growth) and measure edge of the more obvious margin of the zone.
6. Discrete colonies growing within the inhibition zone may represent a mixed culture or resistant variants; subculture single colonies from the primary culture plate, re-identify, and retest for susceptibility. If the discrete colonies are still apparent, measure the colony – free inner zone.

G. Interpretation and Reporting

Use criteria specified by the CLSI to interpret the zone of inhibition for each         antimicrobial agents and report categorical result as either susceptible(S), intermediate (I), or resistant (R).

Figure 1: Antibiotic Susceptibility test of a bacterial isolate.

precautions

The following common sources of error should be investigated to verify that:

• Zone diameters were measured and transcribed correctly;
• The turbidity standard has not expired, is stored properly, meets performance requirements, and was adequately mixed prior to use;
• All materials used were within their expiration dates and stored at the proper temperature;
• The incubator is at proper temperature and atmosphere;
• Other equipment used (e.g., pipettors) are functioning properly;
• Discs are stored desiccated and at proper temperature;
• The control strain has not changed and is not contaminated;
• Inoculum suspensions were prepared and adjusted correctly; and inoculum for the test was prepared from a plate incubated for the correct length of time and in no case more than 24 hours old.

RLABB Inauguration program

RLABB in KCMS

Research Laboratory for Biotechnology and Biochemistry (RLABB) is now in Kantipur College of Medical Science (KCMS), Sitapaila, Kathmandu. Some of photographs of Inauguration of RLABB-KCMS are presented here.

Inauguration of RLABB-KCMS Branch by Honorable Minister of Environment, Science and Technology in presence of other respected delegates from different sectors.

MOU (Memorandum of Understanding) signed between Executive Director of RLABB, Prof. Dr. Vishwanath P. Agrawal and Principal, KCMS, Mr. Kedar Ji Kandel on June 07, 2012 in presence of Honorable Minister of Environment, Science and Technology and other respected delegates from different sectors at KCMS premises.

Invited chief guest, Honorable Minister of Environment, Science and Technology and other respected delegates from different sectors at KCMS premises (From left: Dr. Ganesh Agrawal, Head, Central department of Chemistry, Dean, TU, Head, KCMS, Executive Director, RLABB, Honorable Minister, Principle, KCMS and NESOM president.

Invited guests and respected delegates attending the program.

Lab visit

NOTE: All interested scientists and students are heartily welcomed to work in RLABB-KCMS branch.