General Microbiology

Question 1

1)Monitrichous
2)Amphitrichous
3)Lophoteichous
4)Periteichous

Answer 1

1)Vibrio Cholerae
2)Alcaligenes faecalis
3)Spirilla
4)Typhoid bacilli

Question 2

Demonstration of flagella of bacteria

Answer 2

1)Dark field Microscopy
2)special staining methods
3)Electron Microscopy
4)Indirect Methods
-Hanging drop or under a cover slip :
-Spread of bacterial growth over a film of agar:eg. Swarming of proteus sps.
- Turbidity spreading through semisolid agar:eg.Craigie’s Method

Question 3

Demonstration of fimbriae of bacterium

Answer 3

1)Electron Microscopy
2)Hemagglutination test

Question 4

Types of fimbriae

Answer 4

Type 1 : Mannose -sensitive
Type 2 & Type 3 : Mannose -resistant
Type 4 :

Question 5

Metachromatic /Volutin/Babes-Ernst granules

Answer 5

Highly refractive basophilic bodies consisting of polymetaphosphate .
They are found in diptheria bacillus ; plague bacillus: Yersinia pestis ; Mycobacteria: Mycobacterium tuberculosis

Question 6

Intracytoplasmic Inclusion bodies staining techniques

Answer 6

1)Methylene blue or touledene blue stain: stains a red violet color.
2)Neisser and Albert staining :
3)Acid -fast staining: Volutin granules are slightly acid-fast resisting decolourisation by 0.1% sulphuric acid
4)wet films :
4)Electron microscopy

Question 7

Staining of Nucleoid of bacteria for seeing under light microscope is

Answer 7

Feulgan staining

Question 8

Causes of endospore heat resistance :

Answer 8

Calcium -dipicolinate ;acid soluble protein stabilization of DNA ;protoplast dehydration;spore coat ;DNA repair ;greater stability of cell proteins in bacteria adapted to growth at high temperatures and others

Question 9

Demonstration of spores of bacteria

Answer 9

1) Gram staining:unstained refractile body within the cell
2)Modified Ziehl-Neelsen Stain:decolorizer :0.25 to 0.5 % H2SO4

Question 10

Generation time for
1) Coliform bacilli
2) Tubercle bacilli
3)Leprae bacilli

Answer 10

1) 20 minutes
2) 20 hours
3) 20 days

Question 11

Determination of viable count

Answer 11

1) Dilution Method:used in presumptive Coliform count in drinking water.
2) Plating Method :
a)Pour -Plate Method
b)Spread plate Method-in which serial dilutions are dropped on the surface of dried plates and colony count is obtained

Question 12

1)Obligate aerobes
2)facultative anaerobes
3)Microaerophilic
4)Obligate anaerobes

Answer 12

1) Vibrio cholera
2)Staphylococcus spp.;Escherichia coli
3)Campylobacter spp. ; Helicobacter spp.
4) Clostridium tetani ;Bacteroides fragilis

Question 13

Capnophilic

Answer 13

Bruccella abortus ; Pneumococci. ; Gonococci

Question 14

Thermal.death point

Answer 14

Minimum time required to kill a suspension of organisms at a predetermined temperature in a specified environment.

Question 15

Tyndallization

Answer 15

An exposure of the steam at 100⁰C for 20 minutes on three successive days is called tyndallization or intermittent sterilization

Question 16

Peptone

Answer 16

It is a complex mixture of partially digested proteins .The important constituents are peptones ,proteases , amino acids and amino acids and a variety of inorganic salts including phosphates , potassium and magnesium and certain accessory growth factors such as nicotinic acid and riboflavin.

Question 17

Special enriched media

Answer 17

1)Blood agar: for Streptococcus,
Pneumococci, haemophilus
2)Chocolate agar: for Nisseria , Gonococci, haemophilus
3)Bordet-Gengou agar: for
Bordetella
4)Loeffler’s serum slope: for isolation of cornybacterium diptheriae
5)Dorset’s egg medium :used for the cultivation of mycibacterium tuberculosis and cornybacterium diptheriae

Question 18

Special Enrichment media

Answer 18

Enrichment media is a media which allows a growth of a particular organism but not others
Examples include :
1)Tetrathionate broth:inhibits coliforms while allowing typhoid-paratyphoid bacilli to grow freely in the fecal sample.
2)Selenite F (F for Feces) broth:used for dysentery bacilli
3)Alkaline peptone water:used for V.cholerae from feces

Question 19

Special selective media

Answer 19

Selective media inhibits the growth of unwanted bacteria by inhibitory agents such as dyes , bile salts , alchohols , acids and antibiotics .
Examples include :
1)DCA (deoxycholate citrate agar): for dysentery bacilli (isolation of shigella)
2)Wilson Blair’s brilliant green bismuth sulfite agar medium:for the isolation of typhoid and paratyphoid bacilli
3)Lowenstein-Jensen medium:for Mycobacterium tuberculosis
4)Thayer -Martin medium:for isolation of gonococci and meningococci
5)Potassium tellurite medium:Isolation of diphtheria bacilli
6)TCBS (Thiosulphate ,citrate,bile salts , sucrose agar): for Vibrio cholerae

Question 20

Special indicator media

Answer 20

Indicator media contains an indicator which changes its color with the concentration of the product
Examples include :
1)Wilson -Blair medium: incorporation of the sulphite to the medium .The S. Typhi reduces sulphite to sulfide in the presence of glucose and the colonies of S.Typhi have a metallic sheen.
2)potassium tellurite :in McLeod medium is reduced to metallic tellurium by the diptheria bacillus to produce black colonies.
3)MacConkey agar:indicates the fermenting property.Lactose fermentors produce pink coloured colonies while others produce colourless colonies due to neutral red indicator.

Question 21

Special differential media

Answer 21

Differential media contain substances that bring out differing characteristics of bacteria and thus helping to distinguish between them is called differential medium .
1)Blood Agar:to distinguish between hemolytic bacteria (,e.g. many streptococci and staphylococci isolated from throats) produce clear zones round their colonies because of red cell destruction.
2)Nagler’s medium:enables us to view lecithinase activity.
3)MacConkey agar :
Lacose fermentors eg:Esch. coli , Klebsiellae sp.
NLF eg.Salmonella ,shigella,proteus
LLF eg Shigella sonnei

Question 22

Special sugar Media

Answer 22

Sugar used for sugar Media : any fermentable substance . They may be
1)Monosaccharides :
a.Pentoses eg.arabinose,xylose,rhamnose
b.Hexoses eg. Glucose , fructose , Mannose,sorbose,galactose.
2)Disaccharides eg.Sucrose ,Maltose,lactose,threalose,cellobiose.
3)Trisaccharides eg.raffinose.
4)Polulysaccharides eg.starch, insulin,dextrin,glycogen.
5)polyhydric alcohols eg. glycerol,eruthriotol,adonitol, mannitol,dulcitol , sorbitol,inositol.
6)Glycosides eg.salicin, aesculin
7)organic acids eg.tartarate,citrate, mucate,gluconate ,malonate.

Question 23

Special transport media

Answer 23

Examples
1)Stuart’s transport medium and amies transport medium for gonococci
2)Buffered glycerol saline for enteric bacilli
3)Pike’s medium for Streptococcus pyogenes,Pneumococci,and Haemophilus influenzae in nose and throat swabs
4)Cary-Blair medium for V.cholerae and Campylobacter
5)Venkataraman-Ramakrisnan (V-R ) fluid (pH 9.2) for V.cholerae
6)Alkaline peptone water (pH 8.6) for V.cholerae

Question 24

Anaerobic media

Answer 24

1) Thioglycollate broth
2)cooked meat broth or RCM (Robertson’s cooked meat ) broth