KOH String Test Lab Report

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Introduction: Bacteria are very diverse and are part of the prokaryotic domain. Some bacteria can be harmful, but others can also be beneficial in many ways. There are bacteria everywhere on Earth; places that you would think would have bacteria, like your gastrointestinal tract or our skin (Wenner, 2007). Although bacteria are small in size and are a simple cell organism, it is essential to life. There are different ways in how to distinguish and classify bacteria. One way is you can look at it visually. You can describe if the whole colony is punctiform, circular, rhizoid, irregular, or filamentous. You can describe the edge as entire, undulate, lobate, filamentous, or curled. You can describe the surface as smooth, glistening, rough, …show more content…
It also shows the results from the KOH string test. As you can see all test show that the bacteria is gram-positive. The KOH string test is supposed to determine either the bacteria is classified as gram-positive or gram-negative (Sadava, 2011). We dropped KOH with our bacteria and mixed it. After about a minute, we should have been able to tell if a string has formed or not. We have didn’t have a string form, so we had gram-positive bacteria and a negative string test result. We then did other tests because the string test has a high possibility for false negatives and results can be inconclusive. We swabbed out bacteria on different mediums such as: vancomycin, EMB-lactose, and PEA. There was no growth on vancomycin and EMB-lactose, which makes them gram-positive results. Gram-positive bacteria can’t grow on those two mediums (Leicht, 2015). The EMB-lactose agar has lactose and sucrose for energy. So the sugars are fermentable substrates, which only allow gram-negative bacteria to grow, not gram-positive (Cheeptham, 2014).

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