Lab 3 Discussion.docx

DISCUSSION Streaking is a technique used in microbiology to isolate a pure strain from a single species of microorganism, often bacteria. A microbiological culture can be grown so that the organism can be identified, studied or tested. A sterile cotton swab or inoculation loop was sterilized and dipped in a broth or specimen containing bacteria. Then loop was then spread across one quadrant of an agar plate containing a growth medium which has been sterilized in an autoclave. This introduces a solution of the bacteria to substrates which provide them nutrients. Choice of which growth medium to use depends on which microorganism was being cultured and which was being selected for. Growth media was usually based on the agar, gelatinous substance derived from seaweed. The loop was re-sterilized and dragged across the inoculated quadrant of the streak plate. (Elbing Karen & Brent, Roger. (2002)). This was done to collect some bacteria on the loop. The loop was spread around another fourth of the plate much like the previous step. The loop was sterilized and the procedure was repeated. Each time the loop gathers fewer and fewer bacteria until it gathers just one single bacterial cell that can grow into a colony .The streak plate was then incubated, for 2 hours to allow bacteria to reproduce. At the end of incubation there should be enough bacteria to form visible colonies in the area touched by the inoculation loop. There a 4 type of techniques used in this experiment. The first one was the transfer of microbial culture from nutrient broth to agar plate by streaking. This was most common method to observe colony morphology and to work with individual colonies for diagnostic methods. The pattern of growth of bacteria shows in four different directions.

Figure 1 : Microbial culture from nutrient broth to agar plate by streaking

Second type technique had been used was transfer of microbial culture from nutrient broth to agar slant by streaking method. Slant was a tube of solid medium at an angle. Tube was easy to store and transport. The pattern of growth pf bacteria showed the zigzag pattern and can see colony morphology but in small surface area.

Figure 2 : Microbial culture from nutrient broth to agar slant by streaking method

Third techniques used in this experiment were transfer of microbial culture from agar plate to broth bottle. Broth was in a liquid medium. These techniques which in tube was easy to store and transport but cannot saw colony morphology. After conducted the experiment, it showed Pseudomonas sp. grown at the bottom.

Figure 3 : Microbial culture from agar plate to broth bottle

Last techniques had been used in this experiment was transfer of microbial culture from agar plate to agar deep by stabbing technique. Agar deep was in tube of solid or semi-solid medium. It was good for organisms that prefer reduced oxygen and to evaluate motility. The result showed, the microbial of Pseudomonas sp. was formed a layer at the top in order it needed for oxygen.

Figure 4 : Microbial culture from agar plate to agar deep by stabbing technique

REFERENCE Elbing, Karen & Brent, Roger, (2002), Growth on Solid Media, Current protocols in molecular biology Chapter 1, Unit 1.3.