Unknown Bacteria Essay

The unknown bacteria A and bacteria B have to be identified by its genus and species. First both bacteria had to be inoculated into a TSA agar media using the streak plate method. Four quadrants were drawn, so that the bacteria could be isolated as much as possible. Each bacteria was inoculated into two different plates, so that one could be incubated at 37 degrees Celsius and the other at 25 degrees Celsius. Bacteria B, which was incubated at room temperature showed red colonies throughout its media. This identified it as the gram-negative bacteria Serratia marcescens, but further tests had to be conducted to fully confirm. Bacteria A showed a white opaque growth in both of its plates.
Secondly both bacteria had to be gram stained, so that they could be identified as gram-positive or as gram-negative. The same gram staining method was used for both bacteria, which consisted of inoculating each bacteria into a
The lactose test appeared pink still, which indicated no fermentation had happen and no gas was found either. The sucrose test appeared yellow indicating that sucrose was fermented turning the tube acidic and surprisingly no gas was found. After these tests and with the red growth on the TSA media it was confirmed that it was indeed the bacteria Serratia marcescens. In the gram-positive bacteria tests the MSA media turned completely yellow, which indicated mannitol was fermented turning the plate acidic. The glucose-bromocresol purple tube appeared completely yellow as well indicating glucose was fermented which turned the agar acidic. The bacteria Staphylococcus aureus was identified because it's the only gram-positive bacteria, which is able to turn both MSA and glucose-bromocrosel tests acidic, which gives them their yellow appearance. No further testing was needed to identify the two