A Salmonella-specific transcriptional regulator controlling biofilm formation and virulence

FIGUEROA, N. R.; SONCINI, F. C.; ECHARREN, M. L.

Ciudad Autónoma de Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias, LIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2017

Sociedades de Biociencias

Salmonellosis is among the most common foodborne diseases, with millions of human infections occurring worldwide every year. A key aspect of Salmonella?s life cycle that contributes to its high prevalence is its ability to form biofilms, bacterial communities embedded in a self-produced extracellular matrix that allows them to adhere to each other and to diverse surfaces. This multicellular behavior facilitates persistence and transmission between hosts, and survival in the environment. In Salmonella, the extracellular matrix is composed mainly by cellulose and curli fimbriae whose synthesis are controlled at transcriptional level through the expression of its master regulator, CsgD. Expression of this transcriptional activator is in turn finely regulated by several transcription factors that integrate different environmental signals. We identified a previously uncharacterized Salmonella-specific transcription factor, MlrB, that, according to in silico analysis, could participate in the control of biofilm-formation. Overexpression of the gene coding for this factor in different genetic backgrounds provoked marked differences in the characteristic Salmonella biofilm morphotypes, as well as on the expression of its target genes, including csgD, determined by the use of chromosomal reporter fusions to lacZ. Our results demonstrate that under specific conditions this Salmonella transcription factor affects biofilm-formation by controlling the induction of the Csg regulon, and hence in switching between planktonic and sessile lifestyles. In addition, we determined that it expression is maximal under conditions relevant to the infection, which is in agreement with the regulation observed for members of the SPI-2 locus, allowing us to postulate it as a link between the biofilm formation and Salmonella pathogenesis.