Methods in Microbiology (GATE - XL)

Alpha-hemolytic colonies produce zone of partial clearing on blood agar. Alpha hemolysis is caused by hydrogen peroxide produced by the bacterium, oxidising hemoglobin to green methemoglobin.

Gram-positive cocci produce colonies on Columbia nalidixic acid agar. Columbia nalidixic acid agar with sheep blood is a selective microbiological medium.

Cary Blair medium is a transport medium for the collection and shipment of clinical specimens. The low nutrient content of the medium and the inclusion of phosphate buffer prevent bacterial overgrowth by E. coli, Citrobacter freundii and Klebsiella aerogenes. It can occur in other transport mediums containing sodium glycerophosphate. The low oxidation-reduction potential of the medium ensures bacterial survival over long periods.

Salk polio vaccine is sterilised by formaldehyde (gaseous form).

The most probable method of obtaining a pure culture is by streak plate method. Individual colonies can be obtained in the fourth quadrant.

Calcium provides heat resistance to endospores. Calcium forms calcium dipicolinate in endospores. It may aid in resistance to heat and oxidising agents.

Cobalt is required for the synthesis of leghemoglobin and for the growth of legumes relying on symbiotically fixed nitrogen. It is an essential micronutrient. It has been established that rhizobium and other N₂ fixing microorganisms have an absolute cobalt requirement whether or not they are growing within nodules and regardless of whether they are dependent on a nitrogen supply from N₂ fixation or from mineral nitrogen.

Blood agar is enriched with sheep blood and it also aids in identifying bacteria on the basis of different hemolysis patterns.

The suspected organism is campylobacter as it is a strict microaerophile. Confirmatory test can be done by plating on Butlezr's virion, which is selective for campylobacter.

Propionibacterium is an obligate anaerobe. For anaerobic culturing, palladium is required as a catalyst. It is only able to work if it is not dry and is not inactivated by H₂S or other products of bacterial metabolism.

MSA contains a high concentration (~7.5%-10%) of salt (NaCl).

Selenite F broth is also recommended for the transport of strains of Vibrio cholerae. These organisms can survive for 2 to 5 days in Sodium Selenite broth.

The 263K scrapie prion is inactivated at 121-132 degree centigrade for 60 minutes.

Lucas semisolid indicator is used to indicate anaerobiosis in a jar. It is based on the reduction of methylene blue. In an anaerobic environment, it is reduced from its coloured oxidised form to colourless reduced leuco compound.

The phase contrast microscope makes it possible for biologists to study living cells and how they proliferate through cell division. Thus, it helps in visualising live processes.