Bacteria in dense environments, like the human microbiome, respond to the actions of neighboring cells. Our goals are to understand how bacteria recognize their neighbors and respond accordingly on a molecular scale. Specifically, we study social recognition systems in the opportunistic pathogen, Proteus mirabilis, found in human guts and causes recurrent catheter-associated urinary infections. While these systems use the type VI secretion system for transfer between cells, they have unique mechanisms for social recognition. Read more at:

• Wenren, L., et al. "Two independent pathways for self-recognition in Proteus mirabilis are linked by type VI-dependent export." (2013)

• Cardarelli, L., et al. "Two proteins form a heteromeric bacterial self-recognition complex in which variable subdomains determine allele-restricted binding." (2015)

• Chittor and Gibbs. "The conserved serine transporter SdaC moonlights to enable self recognition." (2022)

• Knecht, A., Sirias, D., et al. "Non-cognate immunity proteins provide broader defenses against interbacterial effectors in microbial communities." (2023)

Collective behavior in P. mirabilis and other bacteria is linked to fitness and virulence. We study how the interactions between bacteria can act as a form of micro-crowdsourcing and lead to changes in macro-scale behavior. Specifically, we focus on the collective motility of swarming, where bacteria travel centimeter-wide distances in direct coordination with their neighbors. Many questions abound about how this movement occurs and how social recognition impacts this coordination. To read more about our work in this area, see:

• Little, K., et al. "Cell shape and population migration are distinct steps of Proteus mirabilis swarming that are decoupled on high-percentage agar." (2018)

• Tipping, M., et al. "Peer pressure from a Proteus mirabilis self-recognition system controls participation in cooperative swarm motility." (2019).

A bacteria's ecosystem comprises many moving parts, including environmental factors like antibiotics and pH levels, host immune systems, phages, and other bacteria. As such, we study these fast-moving bacteria in their native environments to understand how they navigate these changing environments. We use a combination of publicly available metagenomes, collaboration with mouse facilities, and generating datasets ourselves.  Stay tuned for more. 

The organisms we study are fast-moving, shape-shifting bacteria found in low abundance in various ecosystems. As such, we must adapt technologies like biochemical assays, live-cell imaging, and metagenomics to work with these microbes. You can explore more in these papers:

• Little, K., et al. "Cell shape and population migration are distinct steps of Proteus mirabilis swarming that are decoupled on high-percentage agar." (2018)

• Little K and Gibbs KA. "Analysis of Proteus mirabilis social behaviors on surfaces." (2019)

• Tipping, MJ and Gibbs, KA. "Growth recovery assay and FACS-based population sorting following territorial exclusion in Proteus mirabilis." (2020)

• Knecht, A., Sirias, D., et al. "Non-cognate immunity proteins provide broader defenses against interbacterial effectors in microbial communities." (2023)