And how do all those bugs eat the benzene?
Carla Pérez Mon
Benzoic acid is an organic substance that can be found everywhere in nature. It forms part of the proteins of all living organisms and it is very abundant in plants, where it contributes to the construction of their cell walls. Although it is a common substance, it is very difficult to degrade; in other words, it is hard to break it into its smaller pieces. Only microorganisms have evolved the ability to degrade benzoic acid and they do so by numerous biological routes that are controlled by oxygen.
The degradation of benzoic acid has been largely study in laboratories, thus using single bacteria species that are able to grow outside their natural medium. However, benzoic acid degradation is poorly understood in natural communities, in other words; is it not known what it would happen if instead of having a single bacterium in the laboratory, you would have a whole group of different bacteria (bacterial community) growing together in the same medium and forced to degrade benzoic acid. Would they be able to eat the benzoic acid and hence grow? If so, how fast would they degrade the substance and how fast would they grow? Would it be a group of “fast eaters” bacteria which would be able to grow faster and take over the community? Would it make any difference for the process if the oxygen levels changed? Those are the main questions that I addressed in my investigation.
I collected water from a Swedish lake, which contained the bacterial community -‐ the group of different bacteria -‐, and I “forced” them to use benzoic acid by adding the compound to the water. I subdivided the water with the BA added in different groups (samples) and I put the bacterial community within each of the groups to grow under high amounts of oxygen, low amounts of oxygen or not oxygen at all (oxygen conditions). I observed that the bacterial community was able to grow more under low amount of oxygen and that this translated to an increase in the rate of benzoic acid degradation. I identified the bacteria groups within the communities using genetic tools. I could not find any group of bacteria especially good in degrading benzoic acid and thus able to grow more than other members in the community for any of the oxygen conditions. On contrary, I observed that the groups of bacteria and their proportions were very different within the communities, even for the samples that were grown under the same oxygen conditions.
All in all, my results suggest that many different bacteria are able to degrade benzoic acid equally well, at least in my studied bacterial communities. Thus, the breakage of the substance would mainly depend on how many bacteria are present in the media rather than who is present there.
Degree project in Biology, Master of Science (2 years), 2016
Examensarbete i biologi 30 hp till magisterexamen, Uppsala universitet, 2016 Biology Education Center and Dept of Ecology and Genetics / Limnology Supervisors: Martha Schattenhofer and Stefan Bertilsson