Сборник текстов на казахском, русском, английском языках для формирования навыков по видам речевой деятельности обучающихся уровней среднего образования

 To identify the bacterial unknowns in a mixed culture by morphological and biochemical methods.

Principle:

The identification of bacteria is a careful and systematic process that uses many different techniques to narrow down the types of bacteria that are present in an unknown bacterial culture. It produces benefits for many aspects of the research of microorganisms and helps physicians correctly treat patients. Multiple tests were performed to provide the fermentation abilities, presence of certain enzymes, and certain biochemical reactions. Qualitative observations were made on the tests, which were compared to unknown bacteria identification key to aid with the identification process. 

Various steps involved in the identification of unknown bacteria are:

Isolation: The importance of this step is to isolate pure colonies of bacteria. The streak plate is a qualitative isolation method; quadrant streaking is mostly done to obtain pure colonies. The inoculation of the culture is made on the agar surface by back and forth streaking with the inoculation loop over the solid agar surface. This will make a dilution gradient across the agar plate. Upon incubation, individual colonies will arise from the biomass.

The characteristics features of the colonies on solid agar media are then noted. This include

Shape : circular, irregular or rhizoid.

Size: small, medium, large( or in millimetres).

Elevation: elevated, convex, concave, umbonate/umbilicate.

Surface: Smooth, wavy, rough, granular, papillate or glistening.

Edges: entire, undulate, crenated, fimbriate or curled.

Colour: Yelow, green etc.( Note the colour of the colony).

Structure: opaque, translucent or transparent.

Degree of growth : scanty, moderate or profuse.

Nature: discrete or confluent, filiform, spreading or rhizoid.

In order to obtain the pure culture of organism, the isolated colonies are aseptically transferred on to different nutrient agar slant tubes and incubated overnight at 37 degree Celsius. It is then stored for future purpose.

 Staining Reactions:

Fig 1: Simple staining of cocci

Biochemical reactions:

Gram negative enteric bacilli play an important role in the contamination of food. Hence they are the main causative agents of intestinal infection. Gram negative family includes Shigella, Salmonella, Proteus, Klebsiella,Escherichia,Enterobacter etc. Usually four tests are used for differentiation of the various members of Enterobactericeae. They are Indole test,Methyl red test, Voges proskauer test and Citrate test; collectively known as IMViC series of reactions.