Bacterial Architects
“…the spatial structure generated as a consequence of T6SS-mediated killing can favour the evolution of public-goods cooperation…” McNally, et al 2017. Nature Communications
Dynamic bacterial activities shape and are shaped by their surroundings. We’ve explored how chemical communication among bacteria in an insect alters the composition of microbes within the host community (Sela, et al. 2020). Working with our peers in the CMDI, we mathematically predicted and then showed that bacteria wielding a weapon called the Type Six Secretion System (T6SS) can reorganize the members of an attached biofilm, allowing the warring factions to coexist by occupying spatially distinct locations where sharing is possible (McNally, et al. 2017). Ongoing collaborations with Peter Yunker’s physics group explore how chemical and physical forces build bacterial communities (Bravo, et al. 2023). Our insights reveal that the full, functional capacity of bacteria is a property that emerges from the architecture and spatial organization of communities of cells in which they live and they die.
Initially well mixed populations of docile V. cholerae T6SS– “killer” cells remain mixed (top), but T6SS+ killers with distinct weaponry undergo a process of phase separation, like water and oil, into distinct clonal patches (bottom). Shown are predictive models (left) and images of colonies of fluorescence cells (right).
The Bacterial Toolbox
“…the microfluidic device is a powerful tool to measure cell-to-cell communication, which can be extended to future studies of bacterial sensing and diagnostics” Austin et al. 2017. Biomicrofluidics
We actively engage in applied research and in bioengineering. We have collaborated with CDC scientists to harness DNA sequences to track outbreaks of the disease cholera, caused by V. cholerae (Katz, et al. 2013). In prior studies and currently, we work with engineers to harness the DNA that encodes bacterial communication systems (Austin, et al. 2014). We are developing new tools with Mark Stycznski’s group in Chemical & Biomolecular Engineering to sense chemical molecules that can be used to diagnose ailments. We are also leveraging our expertise in bacterial genetics with GTRI colleagues to engineer bacteria that can behave like probiotic-like vaccines to stimulate the immune system. Built on our strong foundation in bacterial genetics and the study of fundamental cell-to-cell processes, we translate microbial mechanisms into solutions for human health and technology.
Blue “sender” bacterial cells, separated by a porous membrane (grey) in a microfluidic device, talk with QS signals to “receiver” cells that respond by turning green.
Bacterial Ecology and Evolution
“…pathogens can manipulate host biomechanics to redefine gut communities. Logan et al 2018. PNAS
Studying bacteria on a lab petri dish tell us what they can do, but not when, why and how they coordinate these tasks in the real world. Our research in microbial ecology contextualizes the molecular mechanisms that govern bacterial behavior in natural, complex communities. In a prior study with collaborators, we demonstrated that the pathogenic bacterium V. cholerae uses its T6SS weapon to displace the resident microbes in the gut of fish by inducing spasms that expel the competitors (Logan et al, 2018). We are currently challenging assumptions in our field regarding the cost and ubiquity of the T6SS in bacteria. More recently, we have begun hunting for the genes that allow a newly discovered “social” cave bacterium to aggregate to produce multicellular structures that aid in dispersal. We are also expanding our focus to marine conservation by collaborating with Lauren Speare’s lab in the CMDI. We are probing the complex interactions between coral hosts, their microbial symbionts, and resident Vibrio pathogens to understand and control coral loss. These emerging projects seek to define the molecular steps that bacteria use to drive the ecology of natural systems.
Fluorescently labeled resident Aeromonas (A) remain in the zebrafish GI tract when T6SS– V. cholerae enter (top), but are eliminated by T6SS+ V. cholerae (bottom). V. cholerae is unmarked in these experiments.