Wednesday, 18 February 2015

A PRACTICAL WORK ON THE IDENTIFICATION OF BACTERIAL SPECIES


About Test For Bacteria

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.

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