“Sharing the matrix” – a cooperative strategy for survival in Salmonella enterica serovar Typhimurium

Bacteria in nature live together in communities called biofilms, where they produce a matrix that protects them from hostile environments. The components of this matrix vary among species, with Salmonella enterica serovar Typhimurium (STm- WT) primarily producing curli and cellulose, which are regulated by the master regulator csgD. Interactions between bacteria can be competitive or cooperative, with cooperation more commonly observed among the kin population. This study refers to STm- WT as the generalist which produces all the matrix components and knockout strains that are defective in either curli or cellulose as the specialists, which produces one of the matrix components but not both. We have asked whether two different specialists will cooperate and share matrix components during biofilm formation to match the ability of the generalist which produces both components. In this study, the response of the specialists and generalist to physical, chemical, and biological stress during biofilm formation is also studied to assess their abilities to cooperate and produce biofilms like the generalist. STm WT colony biofilm which produces both the major biofilm matrix component were protected from stress whereas the non-matrix producer ([DELA]csgD), the cellulose, and curli alone producers [DELA]csgA, [DELA]bcsA respectively were affected. During the exposure to various stresses, the majority of killing occurred in [DELA]csgD. Whereas the co-culture ([DELA]csgA: [DELA]bcsA) was able to resist stress like that of the STm WT. Phenotypic and morphological characteristics of the colonies were typed using congo red assay and the Influence of matrix on the architecture of biofilms was confirmed by scanning electron microscopy. Our results show that matrix aids in survival during antibiotic, chlorine, and predatory stress. And possible sharing of the matrix is occurring in co-culture, with one counterbalancing the inability of the other when confronted with stress.