Duke researchers are behind a new and exciting discovery that could help explain the swarming behavior of Vibrio cholerae, the bacterium that causes cholera epidemics. By employing cutting-edge imaging technology, researchers were able to follow the pathways of single bacterial cells as they swarmed out of biofilm communities. Congratulations to Drew Bridges and his team for leading this important study that shows how complex the dynamics of biofilm formation and disassembly can be. Her work uncovers the specific mechanisms that allow these pathogens to move through the environment.
Formation of biofilms by Vibrio cholerae is essential to its survival as well as pathogenesis. These biofilms undergo multiple rounds of assembly and disassembly in which the bacteria can respond to a changing environment. The study shows that when Vibrio cholerae cells emerge from biofilms they have an opportunity to travel and possibly establish infections. Alarmingly, biofilm-forming bacteria, such as Vibrio cholerae, account for as much as 70% of human bacterial infections.
Biofilm Dynamics and Dispersal
Together, these observations suggest that under dispersal conditions, not all Vibrio cholerae cells exit the biofilm. Rather surprisingly, only ~20-25% of the cells are left behind, indicating a highly strategic retention mechanism that perhaps confers to biofilm stability. As the free bacteria begin to exit the biofilm, the overall structure collapses, indicating a delicate balance between attachment and dispersal.
Bridges’ lab examined localized differences in mechanical properties that develop as Vibrio cholerae biofilms form. Their findings show that in some parts of these biofilms, it’s the opposite — areas become more liquid. Paducah, Kentucky This amendment easily permits cells to expand outwards, even from the building’s core. Yet, this fluidity is the key, for it enables this bacteria to jump ship and colonize new ecosystems or hosts.
Additionally, the research used spinning-disk confocal microscopy. This was the first time that Fluorescent Activated Probes (FAPs) technique was used to image Vibrio cholerae biofilms. This advanced imaging technique enabled researchers to observe individual cells in real-time as they moved, disassembled, and dispersed from the biofilm community.
Implications for Understanding Infection Mechanisms
How Vibrio cholerae functions in biofilms will be essential to finding ways to prevent it from causing infections. These findings indicate that these bacteria are insensitive to the limitation of oxygen when ensconced in biofilms. This resilience, combined with improved capacity to survive hostile environments, can make them harder to kill.
Bridges hypothesizes that V. cholerae cells themselves act as a major mechanical constituent within the biofilm. This new concept underscores the importance of the bacteria orientation to structural stability, yet permitting escape through dispersal. The study highlights the importance of investigating the mechanical characteristics of biofilms to better understand how these pathogens proliferate and survive.
The introduction of Vibrio cholerae biofilms may be transenvironmental (between environmental habitats) or transhost/infection (between human hosts and infection sites). Recognizing this understanding is key to creating successful public health outreach efforts to mitigate cholera outbreaks. It deepens our understanding of how bacterial populations move from benign surfaces to fully virulent tissues.
Publication and Future Directions
The findings from this groundbreaking study were published in PLOS Biology and are available under DOI: 10.1371/journal.pbio.3002928. This public health research is deepening the scientific community’s understanding of Vibrio cholerae. It provides a foundation for further research on additional biofilm-forming pathogens.
