Summer research in the Whatley Lab focuses on biofilms. Biofilms are complex structural communities made up of a single or multiple microbial species that secrete a protective layer of matrix. These communities adhere to surfaces in the natural and built environment. For example, they are found in pipes, on rocks in streams, and the human body.
Traditionally, bacteria are studied in their planktonic (free floating) form. However, outside of the lab, bacterial growth is more prevalent as biofilm. The composition of biofilms allows for better bacterial survival overall, as well as under many different conditions. For example, better survival in the presence of antibiotics. Biofilms are much less susceptible to antibiotics than free-floating bacteria. This may be due to the inability of an antibiotic to reach the full depth of a biofilm.
Without studying the biofilm as a whole, you cannot capture the complexity of the interactions between the different bacteria and how this leads to their successful survival in the natural environment. Therefore, to better understand biofilm and the bacteria that live within these communities, we must study both their planktonic and biofilm forms.
In the summer of 2015, Amanda Finck ‘18 and Kelly DiGeronimo ‘17 isolated and identified two species, Microbacterium oxydans and Chryseobacterium hispalense, from a water fountain. They found that these two species are specific and synergistic biofilm partners. Meaning, when allowed to grow with other species apart from each other or individually, neither M. oxydans nor C. hispalense grew as much biofilm as the one they formed together. This summer, we (Sarah DiDomenico and Hannah Hadgu ‘19) explored the lifecycle of biofilm specifically composed these two species. We were interested in capturing the times at which these species adhere (panel 1 of figure 1), grow (panel 2), and disperse (panel 3), in order to better inform our future experiments. To observe biofilm formation overtime, we measured the optical density, which indirectly quantifies the amount of cells present in the planktonic and biofilm growth over a 216 hour time period. Crystal violet stain was used to visualize and measure biofilm biomass. We found that despite the amount of planktonic growth, the species created more biofilm together than apart. Additionally, overall dual species biofilm was greater than the expected sum of the biofilm biomass of the individual species. These results further support the previous findings of a specific and synergistic biofilm partnership.
We realized like M. oxydans and C. hispalense, our lab partnership is also “specific and synergistic”. We found that we are better when working together and supporting each other. A synergistic partnership, such as ours, has created a safe learning and working environment, allowing us to grow as scientists and people at a great speed. Similarly, when M.oxydans and C.hispalense create a biofilm they grow at an exponential degree. Unfortunately, like all biofilms, we must disperse at the end of these 8 weeks.