: Catalase positive and negative bacteria ?



Lactose fermenting also , would be appreciated

In: Biology

Simply explains if your bacteria has the encyme catalase or not. Catalase is used to catalyse the reaction of h2o2 to h2o and o2. H2o2 appears in aerobe living organisms, but since its poisinous we have to get rid of it. If a bacteria has no catalase its most likely that it is an anaerobe living one. The catalase test (does my bacterium have it or not) is used to identify bacteria.

Similar for lactose fermenting, simply not all bacteria are capable to do it.

So back in the bad old days, we needed a better way to tell the difference between the two ubiquitous Gram-positive cocci: Staphylococcus and Streptococcus.

If you pour hydrogen peroxide on a bacterial culture, you can tell the difference! Staph will bubble. Strep will not. The bubbling is due to an enzyme called catalase which all Staph species have but no Strep species does.

Since then, several more catalase positive organisms have been discovered. It remains a useful way to categorize bacteria, though it’s no longer useful for identifying them since the development of better techniques.