Mycobacterium marinum biofilm formation reveals cording morphology

Abstract The emergence of the nontuberculosis mycobacteria (NTM) as clinically relevant pathogens has warranted the study of these ubiquitous organisms in the context of their likely environmental niche, the biofilm. We assayed the NTM bacterium Mycobacterium marinum strain 1218R, a fish outbreak isolate, for biofilm formation on different surfaces over time using three different methods. Using the MBEC system, biofilm development occurred continually over the 14-day culture period reaching a mature or stable biofilm state after 7 days postinoculation. Quantification of M. marinum biofilm formation on high-density polyethylene (HDPE), polycarbonate (PC) and silicon (Si) coupons over a 14-day period was evaluated using a continuous flow reactor system. M. marinum developed biofilms on all of the surfaces tested. However, substantially more biofilm accumulated on the silicon than on the other substrates (Si>HDPE>PC) under the same growth conditions indicating that silicon was the most effective substratum studied for the generation of M. marinum biofilms and suggesting a correlation between surface hydrophobicity and attachment. Finally, confocal laser scanning microscopy was used to visualize M. marinum biofilm development in situ over time and revealed an unusual biofilm ultrastructure. Large cell clusters attached to the surface grew in parallel sinuous arrays of cells that formed large cords.