Essay Example on Growing Bacteria

Pour-plate method

The technique involves coating of the diluted tasters mixed with melted agar medium. The idea behind this is to make the inoculum less concentrated. The process is done in tubes which contain melted agar medium to allow proper distribution of bacteria cells in the medium. The content is then well mixed for excellent results to be obtained. After the material is well assorted, it is then poured onto different Petri plates for it to solidify (Stewart, 2012). It is then incubated, and it is in the incubator that the bacteria colonies separate themselves. Upon keen observation, one can realize that the bacteria colonies develop within the agar medium. The isolated colonies are then taken and put in a separate petri dish to ensure that purity is maintained (Stewart, 2012). The method is useful but it is identified with specific limitations where during the obtaining of the colonies the agar medium has to be dug, and this interferes with other colonies. Similarly, the agar medium only becomes liquid at the 42-45o, and the microbes used in the process should be able to withstand the temperature otherwise they will be destroyed.

Spread-plate method

In this technique, the different culture is not diluted in the agar medium, but instead, the microorganisms are diluted using a sterile solution for instance water or a saline liquid; it is done in separate tubes (Stewart, 2012). After the mixture is formed, a drop from each machine is then put on the middle of an agar plate and spread gently on the surface using a treated bent rod. The spread content is then incubated. When the colonies develop, they are then transferred to a separate plate to make sure that they remain pure (Willmer, 2015). In this method, there are those microorganisms that develop quite well because of the spreading that is done individually.

Streak plate method

Streak plate is a commonly used method where a small portion of the mixed microorganisms is placed on the tip of an inoculation needle and is splashed across the surface of the agar medium. The streaks then isolate the mixture and the cultures separate from each other (Stewart, 2012). A second streaking needs to be done on a plate but without inoculation and the dishes are then incubated for the colonies to grow. The idea behind this method is that when streaking is done a dilution grade is obtained all over the petri dish and the bacterial microorganism is achieved at the surface of the agar (Willmer, 2015). Because of the dilution gradient, the growth of the colonies does not take place on the part of the agent but where the bacterial cells are found. Single colonies are obtained and are re-streaked on a different plate to achieve purity.

It is paramount to note each method follows different guidelines but the results obtained are the same. The pour plate method is versatile because it can be used to get the number of bacterial cells present in a mixture. It, however, has limitations such as during the obtaining of the colonies the agar medium has to be dug, and this interferes with other colonies. Similarly, the agar medium only becomes liquid at the 42-45o, and the microbes used in the process should be able to withstand the temperature otherwise they will be destroyed. The streak method is the most appropriate because more pure bacteria are obtained because of the re-streaking process. Unlike the pour plate method the spread plate does not need to withstand the medium agar temperature, and similarly, there is no fear of extreme temperature destroying the microorganism.

References

Stewart, E. J. (2012). Growing unculturable bacteria. Journal of bacteriology, 194(16), 4151-4160.

Wilmer, E. N. (Ed.). (2015). Cells and tissues in culture: methods, biology, and physiology. Elsevier.