Posted by: loungekitten | October 12, 2009

What I Know About Catalase (Plus A Life Update)

Ying posted the following comment:

can i noe tat
y whn we perform catalase test
we mz we do lastly?
i realize tat it will produce O2
bt thn duno hw to prove tat
y the O2 produce wil affect the colonies…

Ying, it seems as though you have translated your comment from another language, so I am going to do my best to address what I think your basic question is.

Catalase is an enzyme that converts hydrogen peroxide (H2O2) to water (H2O) and molecular oxygen (O2).  It is the fastest-working enzyme known to us.

Hydrogen peroxide is toxic to cells.  Cells contain organelles called peroxisomes which are membrane-enclosed areas of a cell which contain concentrations of catalase (as well as some other enzymes) and work as hydrogen peroxide catalysis factories, if you will.  In humans, hydrogen peroxide is a byproduct of the breakdown of many substances, including lipid molecules and alcohol. The peroxisome’s oxidative functions explain why liver cells contain lots of peroxisomes.

So, Ying, your basic question seems to be asking what effect molecular oxygen has on a bacterial colony.  As far as I know, O2 has no specific effect on a bacterial colony unless it is a colony of strict anaerobes.  I have used the catalase test as a way of identifying the species of unknown bacteria I might have.  Most species of aerobic bacteria have catalase, most likely because they can tolerate exposure to the molecular oxygen byproduct of the catalase reaction.  So if a sample colony of aerobic bacteria has a negative result from the catalase test, it is remarkable and a means of identification.  For example, if you already know that you have a gram-positive, coccus-shaped bacteria species and you perform a catalase test with a negative reaction, you know that it could not be a staphylococcus bacterium, since different species of staphylococcus bacteria are catalase-positive.  Staphylococcus bacteria species are facultative anaerobes.  It is possible that your bacteria are Streptococcus, since Streptococcus species are catalase-negative.

On the other hand, if you have a bacteria colony which is known to you as a gram-negative, rod-shaped bacteria (the type of bacteria that tends to populate intestines) and you perform a catalase test, you should expect a negative result since most enteric bacteria species are catalase-negative.  E. coli and Shigella are gram-negative, rod-shaped bacteria which are catalase-positive.

The catalase test is a simple, inexpensive test to perform.  It is not necessarily a definitive test, but the results of the test can help you determine which other biochemical tests you need to perform to confirm identification of your unknown bacteria and help to eliminate waste of laboratory supplies and your own time.

Hope this helps!


I so wanted to go to the White Horse Farm Craft Show this past Saturday, but I have a lot of catching up to do.

My mother had surgery on Tuesday to replace her aortic valve (for the second time!), fix her PFO, and remove an aneurysm.  She is still in the hospital and we expect her to be released tomorrow.  I only went to three classes last week, one because I had a test, another because it was after the test and I may as well stay on campus to go to the class while I was there, and a lab because there was absolutely no other way or time to make up the work for that lab and the work in that lab is part of one giant 4-week lab and I would have been messed up for the next few weeks if I had not gone.  I also went to work because I had to – I need the money and I don’t want to get written up (one of the downsides of working in an emergency room – there are very strict policies regarding attendance and lateness).

**Note:  I was debating whether or not I should write about my mother’s surgery, since I sort of feel it’s not my place to disclose this kind of information on this forum.  However, I am tired of writing cryptic statements that only people who know me in real life can understand – it’s starting to mess with the context of some of my posts, so I’m compromising.  I don’t want this to become a forum for discussion of my mother’s condition or anything related to her condition (i.e., I do not want this blog to become aortic-valve-replacement central or PFO central).  I will not answer any questions or e-mails regarding mymother’s surgery or her condition.  Thanks in advance for understanding.

So I’ve got laundry to do, food shopping to do, school reading to catch up on, labs to write.  Heck, maybe I’ll even shower. 😉  Luckily, today is part of our 2-day fall break, so I’ve got a fighting chance to catch up.  Plus later I’ve got to run around to the hospital and my aunt’s house (which is where my mother is staying when she is released from the hospital – my aunt doesn’t work, so she has a lot more free time to take care of my mother).

So anyhow, I ended up just being too exhausted to do anything on Saturday.  I had worked the night before until 12:00 AM.

I may make it to Knit Night this Wednesday, I’ll have to see.  I have a huge test on Thursday (I was planning to study for that today).  Plus I don’t know what I’ll be doing for my mother that night.  At the very least, I’ll need to get home and take care of the dogs.  So at any rate, if I go to Knit Night this week, I will most likely be getting there late.

I have been knitting something for my mother.  I figure this will be the best time to knit her main Christmas gift.  I started it while she was in surgery.  I’ll write more about the project another time.  For now, I’ve got to get ready for all the things I’ve got to do today!


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