, Diagnosis an-&& of Shrimp Diseases - Central Institute of ...

Among all these, the streak plate method is the most commonly method, which allowsob.taining pure culture of specific bacterium from mixed bacterial populations. Bacteria froma mixed culture are streaked over the agar surface in a pattern that deposits them further andfurther apart. Towards the end of the pattern, the resulting colonies of different bacteria areseparated from each other. The single individual colonies of different types are then picked upwith the help of a bacteriological loop and streaked on another plate to obtain pure cultures.Purity of the culture should be confirmed by periodic streaking on plates and observing theircultural, morphoiogical and biochemical characteristics.- Table 1. Sterilization methodsMaterials -- sterilised .--- Methods of sterilisation -...All types of glassware like pipettes, tubes, Dry heat methodflasks, petri dishes etc.Hot air oven160°C for ------- 2 hr or 180°C for 1 hr ---Destruction of used, contaminated material,dead animals, tissues etc.Most bacteriological media, glassware /containers, (decontamination of used media),steel items, corlts, rubber materials, filterpads, filter assembly, distilled water, buffers,solutions etc.IncinerationMoist heatAutoclaving 121°C for 15 minMost tissue culture media, antibiotics, sera, Filtrationsolutions containing heat sensitive materials Membrane filters of 0.22 pm 1 0.45 p~n porelike amino ,acids, carbohydrates, biological sizematerials etc.-Cultural and morphological characters of bacteriaFor identification of bacteria, some general cultural and morphological characteristics likesize, shape, pigmentation, opacity of the bacterial colonies on the solid media; cell shape(rods cocci, coccobacilli, comma), sporulation, etc are important and aid in preliminarygrouping of the bacteria. Some of the cultural and morphological characteristics useful fordistinguishing bacteria ari given in Tables 2 and 3.