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The DK Morales Lab focuses on defining the molecular and metabolic programs governing surface penetration by non-motile pathobionts. Currently, we are studying Enterococcus faecalis, a human commensal of the gastrointestinal tract that can cause life-threatening infections. This bacterium can overgrow and form highly dense populations that penetrate the intestinal barriers of susceptible hosts with disrupted intestinal homeostasis. This process, called translocation, enables E. faecalis to exit the intestine, access the bloodstream, and colonize distal anatomical sites, representing a key virulence trait that could be targeted for therapeutic purposes. We use in vitro and in vivo model systems, combined with advanced molecular, biochemical, and genetic approaches, to answer multiple exciting questions:

Current Projects

What metabolic and genetic processes endow bacteria with the ability to penetrate surfaces or translocate across epithelial barriers?

Our work has revealed that Gram-positive cocci, such as E. faecalis, can penetrate and invade diverse surfaces. We found that E. faecalis uses the hexosamine biosynthetic pathway to produce exopolymers mainly formed by poly-N-acetylglucosamine (polyGlcNAc), which are necessary for penetrating both semisolid surfaces and intestinal epithelial cell monolayers. We continue to understand the molecular pathways and environmental signals regulating polyGlcNAc synthesis during enterococcal movement through surfaces. Moreover, our team is elucidating the cues that trigger penetration/translocation and how those signals are sensed by E. faecalis and other surface-penetrating bacteria. Furthermore, we are interested in defining how other gut commensals, such as probiotic bacteria, modulate E. faecalis migration.

How do bacterial aggregates develop during surface penetration?

We determined that E. faecalis forms three-dimensional aggregates covered by and connected with a self-produced extracellular polyGlcNAc-containing matrix during surface penetration and translocation through intestinal cell barriers. While the formation of aggregates promoted E. faecalis migration across surfaces, little is known about the metabolic and physiological states of the enterococci encased in these structures. We found that cells within multicellular aggregates genetically reprogram their metabolism during penetration/translocation toward increased cell envelope and glycolipid biogenesis, which confers superior tolerance to antimicrobials. We are now investigating whether surface penetration is a coordinated process involving complex cell differentiation steps, which may dictate the spatial structure and physiology of the enterococcal aggregates. In addition, we are interested in defining whether other transcriptional and metabolic programs generate diverse E. faecalis subpopulations with specialized roles within the penetrating community; and if those dedicated subpopulations are required for aggregate development, maintenance, fitness, and penetration.

Which host pathways facilitate bacterial movement across epithelial barriers?

In collaboration with the laboratory of Dr. Juan Cubillos-Ruiz, we are investigating how E. faecalis exploits specific host adaptive pathways to cross intestinal epithelial barriers and cause distal infections.

We use multiple in vitro and in vivo models to understand how enterococci trigger epithelial cell dysfunction and local inflammation.

Can E. faecalis penetrate other host tissues?

E. faecalis is also found in the reproductive tract of healthy women. Its prevalence is increased in individuals diagnosed with aerobic vaginitis, a localized vaginal immune response caused by the displacement of female commensals by uropathogens that can be associated with an increased risk of developing urinary tract infections (UTIs). In collaboration with the Department of Urology at Weill Cornell, our lab is dissecting the molecular determinants that allow enterococci to colonize the female reproductive tract and penetrate the vaginal epithelium. To this end, we have established novel model systems to investigate E. faecalis colonization of the vaginal tissues and the ensuing epithelial responses. We have found that enterococcal surface penetration induces major inflammatory programs in host cells that could contribute to vaginitis and additional UTIs.

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