Bacterial Cultures

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Introduction There are three main types of media cultures: enriched, differential and selective. Each of these three cultures have different properties and aid in laboratory settings by distinguishing between different bacterial cultures. Enriched media allow the growth of multiple bacterial organisms due to the fact that they contain vitamins and nutrients, and do not contain compounds to deliberately inhibit the growth of microorganisms (Wessner et al. 2013). On the other hand, differential and selective media are used to differentiate between to similar types of bacteria, and to select for specific bacterial growth while inhibiting others, respectively (Wessner et al. 2013). Two main ways to distinguish bacteria are whether they are Gram…show more content…
In this case EMB inhibits the growth of Gram positive organisms through the use of eosin Y and methylene blue dyes (Dufour et al. 1981). EMB also distinguishes bacterial cultures because it contains lactose as an energy source. In order for the bacterial cultures to grow, they need to be lactose-fermenting bacteria (Dufour et al. 1981). From Table 1, the colour of the Escherichia coli colonies were metallic green, and the colonies of Enterobacter aerogenes were a light purple/pink, while Staphylococcus epidermidis and Enterococcus faecalis had no growth. This is because EMB inhibits the growth of Gram positive bacteria, and through process of elimination, the E.coli and S. epidermidis are Gram negative bacteria. The green colour in E.coli are the by-products of vigorous lactose fermentation and acid formation (Logue et al. 2012). While the pink colour from E. aerogenes is from the by-product of lactose formation and acid formation (Mishra, 2013), the difference between the two is how efficiently they can perform the lactose fermentation process. As the EMB agar tests for Gram negative bacteria, KF streptococcal (KF S.) agar test for Gram positive…show more content…
TSA media contains proteins which would provide the microorganisms with amino acids, vitamins and nitrogenous substances, glucose to provide an energy source and additional components like blood or animal tissue to enable the growth of fastidious microorganisms – microorganisms with complex nutritional requirements.
3. TSA would be categorized as a complex media.
4. No, I would not expect this media to support the growth of all bacteria because there are certain bacteria that are uncultivable in laboratory settings (Stewart, 2012). The only way TSA could potentially support the growth of almost all cultivable bacterium is if the agar plates were made with slightly different amounts/ concentrations of specific nutrients, vitamins and other components for the fastidious bacterial organisms.
5. Selective media allows the growth of specific organisms while inhibiting the growth of others. They have limited nutrients including, but not limited to, specific pH levels, unusually high solute concentrations or chemical components that inhibit the growth of non-target organisms (Wessner et al. 2013). Differential media on the other hand contains dyes or chemicals that help differentiate between bacterial colonies that are often related (Wessner et al.
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