Question

I need help answering these

question. So think about it? The table may help you, and think about stuff we did in lab before the break 5. Below are your Gram stain results. What does this result tell you (consider gram reaction, shape, morphology)? Can you narrow down your unknown a little with this result? Explain your answer, and list your evidence. 6. MSA results Using what you have learned about this media, list everything this result tells you about your bacteria. Be very thorough. Does this result make sense based on your other results? 7. MacConkey results Using what you have learned about this media, list everything this result tells you about your bacteria. Be very thorough. Does this result make sense based on your other results? 8. Blood agar results

Answer 1

5. The gram staining image shows that the bacteria are cocci as they are spherical in shape. Also upon staining they appear violet, this indicates that the bacterium is gram positive. Gram positive bacteria have a thicker peptidoglycan layer and do not have a lipid layer over their cell wall unlike gram negative bacteria. Therefore, while performing gram staining, gram positive bacteria do not lose their primary strain (crystal violet) when washed with alcohol, whereas gram negative bacteria lose their primary stain due to pores formed in their thin peptidoglycan layer and then tae up the counter stain ,safrannin anfd thus appear pink. Two very common gram positive cocci are Streptococcus and Staphylococcus and thus the unnon could be one of them.

6.MSA or mannitol salt agar is a differential medium that promotes the groth of bacteria that can ferment mannitol and can survive in high salt concentration while not promoting the groth of other bacteria. If the bacteria is capable of fermenting mannitol, it produces acidic by products that change the colour of the pH indicator, phenol red, present in the media from pink to yellow. Since the plate has turned yellow, it implies that the bactera can survive at high salt concentrations and utilise mannitol. Most gram negatve bacteria and some gram positive bacteria cannot survive at such salt concentrations. Streptococcus is one such bacterial species hich cannot survive on MSA. Thus , from our nterpretations from the gram staining and MSA results it is most likely to belong to staphylococcus sp.

7. McConkey agar contans lactose , bile salts, crystal violet and neutral red. It s a dfferential media to differentiate beteen gram negative fastidious (pink colonies) and non-fastidious bacteria(yellow). Crystal violet inhibits the groth of gram positive bacteria and thus results seem to correlate. Since the unknown bacteria is gram positive there are minimal or no colonies observed on McConkey agar.The groth of staphylococcus is inhibited, hoever siince it can metabolise lactose, very few pale pink colonies might be observed.

8. Blood agar contains sheep blood. Bacteria that are capable of producing extracellular enzymes that cause hemolysis produce clear zones in the otherwise red coloured media. Staphylococcus is capable of causeing beta- hemolysis and taking all the above results into account the unknown strain could belong to Staphylococcus sp.