Bacteria thrive by adapting to a wide variety of ecological niches. This includes commensals that are a part of the host microbiota or bacterial pathogens colonising a host. In any environment, resources can be scarce and the competition for survival a serious challenge. The structure of a polymicrobial population establishing in a niche relies on competition and cooperation. For example, cooperation arises from the ability of a species to catabolise complex nutrients sources that is then used by other species. Competition aims to eliminate cheaters and foes and relies on a variety of fighting strategies. Polymicrobial communities can be highly complex, and for example up to 40,000 species coexist within the human gut. These populations can adopt a biofilm lifestyle which contributes stability.
The type VI secretion system (T6SS) is an antibacterial weapon that is used by numerous Gram-negative bacteria to gain competitive advantage by injecting toxins into adjacent prey cells. Predicting the outcome of a T6SS-dependent competition is not only reliant on presence-absence of the system but instead involves a multiplicity of factors. Pseudomonas aeruginosa is a dreadful opportunistic pathogen involved in several acute and chronic infections. It possesses 3 distinct T6SSs and a set of more than 20 toxic effectors with diverse functions including disruption of cell wall integrity, degradation of nucleic acids or metabolic impairment. The potency of single T6SS toxin varies significantly from one another as could be measured by monitoring the community structure, with some toxins acting better in synergy or requiring a higher payload.
This presentation will summarise regulatory pathways that are instrumental to the control of biofilm formation and T6SS activity but then mostly focus on the search of novel T6SS toxins that can guide towards the identification of antimicrobial targets.