Is there any competition between two microbes
in food-restricted environment?
For
whatever reason, competition is one of the most important interaction occurring
in nature and take such a large importance in ecology since it affects
community structures and ecosystems.
Several
types of competition subsist in ecology such as “exploitative competition”
often referred as food competition but also “interference competition” in which
individuals of one specie interacts directly with individuals of another specie
with more aggressive behaviour in the aim of becoming predominant towards the
other.
This
study is very interesting since it allows us to focus on competition between
two simple micro-organisms from the same type of environment (digestive system,
human and rodent one) which are Escherichia coli (white colour) and Serratia
marcescens (red colour) and try to see what append in this situation, if
competition there is and which type.
In
order to answer this question, I managed to prepare two different initial
bacteria cultures in order to let them grow individually. Then, I prepared
different environments with five different food quantities (under the form of
glucose, a sugar) but still limited where I put either the two microbes or each
microbes individually, these latter enabling to see how microbes react
individually in the same environment conditions (we call this “negative
control”). After a while in this environment suitable for competition, I diluted
solutions of bacteria cells to keep enough quantity of cells but not too much
that will enable me to observe them on “plates” where they will form colonies
(a large amount of cells with the same genetic information, as we can see on
the first picture above). As for quantification, I decided to focus on number
of colonies (in mixed bacteria environment) and their size (between mixed and
individual bacteria environment).
In
order to answer this question, I managed to prepare two different initial
bacteria cultures in order to let them grow individually. Then, I prepared
different environments with five different food quantities (under the form of
glucose, a sugar) but still limited where I put either the two microbes or each
microbes individually, these latter enabling to see how microbes react
individually in the same environment conditions (we call this “negative
control”). After a while in this environment suitable for competition, I diluted
solutions of bacteria cells to keep enough quantity of cells but not too much
that will enable me to observe them on “plates” where they will form colonies
(a large amount of cells with the same genetic information, as we can see on
the first picture above). As for quantification, I decided to focus on number
of colonies (in mixed bacteria environment) and their size (between mixed and
individual bacteria environment).
This graph is part of my results and
represents ratios of A/B numbers colonies in mixed bacteria plates according to
the glucose concentration (A being E. coli and B being S. marcescens).
We can see that there is a considerable number of S. marcescens colonies
towards E. coli ones since the ratio is clearly lower than 1 except for
the least concentration of glucose where this value is more important (due to
error manipulation).
Other
results concerning surface areas of colonies tend to show that E. coli colonies seem to be bigger when they’re
alone unlike when they’re confronted to S. marcescens whereas S. marcescens colonies tend to be bigger when they’re
confronted to E. coli unlike when they’re alone.
Thus, we can say that predominance of S. marcescens is shown in mixed plates and for all concentrations of glucose, gaining colonies surface area while exposed to E. coli, whose colonies are conversely bigger in negative controls. Nevertheless, we have to take into account the lack of replicates (when we repeat the experiment) due manipulation problems that certainly impacts the reliability of my results. Furthermore, we have to be clear that I can’t prove any competition between microbes but maybe assume that there are at least interactions that led to the possible predominance that I just spoke before.
So, what would be good to do next is first and overall to repeat
the experiment with replicates to have more reliability of the results.
Secondly, it would be very interesting to work at the microscopic scale to have
more criteria to quantify that will bring enough information about competition
of microbes.
If
you want to know more, here are some bibliography links to have more details
about key aspects of my project and information that helped me to do it:
- Utida, S.
(1953). Interspecific competition between two species of bean weevil.
Ecology, 34(2), 301-307.
- Competition
in biology information
on Wikipedia
https://en.wikipedia.org/wiki/Competition_(biology)
v
- Interspecific competition information on Wikipedia
- Competition exclusive principle information on Wikipedia
v - Scramble competition information on Wikipedia
v - Yoon, H., Klinzing, G., & Blanch, H. W.
(1977). Competition for mixed substrates by microbial populations.
Biotechnology and Bioengineering, 19(8), 1193-1210.
v - E. coli information on Wikipedia
https://en.wikipedia.org/wiki/Escherichia_coli
v - S. marcescens information on Wikipedia
https://en.wikipedia.org/wiki/Serratia_marcescens
v - Chramostova, J.,
Mošnová, R., Lisova, I., Pešek, E., Drbohlav, J., & Němečková, I. (2014). Influence of Cultivation Conditions on the Growth of
Lactobacillus acidophilus, Bifidobacterium sp., and Streptococcus thermophilus,
and on the Production of Organic Acids in Fermented Milks. Czech J. Food Sci, 32(5), 422-429.
v - Thayer, D. W., Muller, W. S., Buchanan, R. L., &
Phillips, J. G. (1987). Effect of NaCl, pH, temperature, and atmosphere
on growth of Salmonella typhimurium in glucose-mineral salts medium. Applied
and environmental microbiology, 53(6), 1311-1315.
Here,
you will find the poster of my project in the framework of Petnica
research projects week in Serbia with Paris Descartes university, CRI Paris and
Schueller Bettencourt Fondation :
Acknowledgements
All the teaching team of Petnica, all Bore students.
T. Milosevic for all advices, support, pedagogy and experience
in Petnica Science Center.
G. Baudrin for his support and follow all along research
projects as tutor.
Petnica Science
Center for having given all these opportunities during the stayCorentin Mathé - - Deletang
L2 FDV Bachelor
Paris Descartes & CRI PARIS
