Testing for Anaerobic Bacteria / Results

Up to this point we are still unaware of exactly what bacteria we are growing. Mark suggested that we could test for anaerobic bacteria by seeing if it would grow inside of the agar. If it could grow without oxygen, it would be anaerobic.

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As it says, in humans these are found usually inside the intestines, so it was not really expected for us to find anaerobic bacteria on the face. Bacteria that grows in the presence of oxygen is called aerobic bacteria, which is what we expect to find – by attempting to grow the bacteria INSIDE of the agar by pushing it towards the centre, we can be certain. I found this useful explanation online, which has helped me understand the different types of bacteria that there are and the conditions within which they grow.

Most bacteria may be placed into one of three groups based on their response to gaseous oxygen. Aerobic bacteria thrive in the presence of oxygen and require it for their continued growth and existence. Other bacteria are anaerobic, and cannot tolerate gaseous oxygen, such as those bacteria which live in deep underwater sediments, or those which cause bacterial food poisoning. The third group are the facultative anaerobes, which prefer growing in the presence of oxygen, but can continue to grow without it.

To start with, we melted some clear agar in order to attempt to grow our bacteria inside of … we were able to do this quite quickly in the microwave to avoid the slow process of the water-bath.


Whilst we were waiting for this to melt, we decided to take some gram-stains from our jelly-mould agar which had now been in the incubator for over a week and had grown some really interesting bacteria on it. DSC04657 DSC04658 DSC04659 DSC04660 DSC04664 DSC04666

Once our agar had cooled in the ice tray, we were able to turn it out and start discussing our methods for testing anaerobic and aerobic bacteria. We had managed to fill 1 & 1/2 jelly moulds. DSC04667 DSC04668 DSC04669

We decided the best way to do it was to use the ‘scraper’ to remove a very small sample of bacteria from our previous jelly mould and just push it towards the inside of the agar, making sure to get as much as possible inside of the agar itself. DSC04670 DSC04671

As you can see, we made many pinpoints to try and have the best spread and opportunity to get results. DSC04672 DSC04673 DSC04674 DSC04675

This was then incubated at room temperature for a few days and grew really well, however – it did not grow inside the agar. This tells us that we have AEROBIC bacteria, as expected, which helps narrow down the bacteria that we could be working with here.



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