Microbes Can Be Picky Eaters
Just like when people choose their lunch from a menu, microbes prefer some foods over others. Most microbes prefer to consume glucose first over other available carbon sources. However, Pseudomonads function differently, prioritizing the consumption of organic acids over glucose.
We have shown in our recent paper in npj Biofilms and Microbiomes that biofilms of a clinical isolate of Pseudomonas aeruginosa preferentially consume lactic acid over glucose. This process is a type of carbon catabolite repression (CCR) known as ‘reverse diauxie’ that has been observed before in other P. aeruginosa phenotypes. Both energy sources were catabolized completely by the biofilms, which did not exhibit the acetate secreting ‘overflow’ metabolism typical of E. coli and many other model microorganisms. These results are noteworthy because reverse diauxie necessitates a terminal electron acceptor like oxygen, which is typically in low supply in biofilms due to diffusion limitation. Furthermore, the coexistence of different microbes with complementary CCR strategies might enhance the overall efficiency and stability of a given microbial community. We also found the key lactate catabolizing enzyme, lactate dehydrogenase, and dozens of other proteins to be associated with biofilm formation, out of about 400 proteins that we isolated overall from these cultures. The complexity of this response shows that exploration of the proteome is critical to understanding microbial metabolism.