SERRATIA MARCESCENS SlpE METALLOPROTEASE IS REGULATED BY Fur AND IT IS EXPRESSED WITHIN EPITHELIAL CELLS

JAVIER FERNANDO MARISCOTTI; ELEONORA GARCÍA VÉSCOVI

Evento virtual debido a la pandemia 2020

Congreso; SAIB-SAMIGE Joint Meeting 2020 on line; 2020

SAIB - SAMIGE

Serratia marcescens is an opportunistic human pathogen that represents a growing problem for public health, particularly in hospitalized or immunocompromised patients. Despite its clinical prevalence, factors and mechanisms that contribute to Serratia pathogenesis remain unclear. S. marcescens ability to adapt to and survive in both hostile or changing environments also relates to the bacterial capacity to express a wide range of secreted enzymes, including chitinases, phospholipase, hemolysin, nuclease and proteases, including the metalloprotease SlpE which is produced in our clinical strain. Recent studies showed that SlpE is secreted by the LipBCD transporter, and point to this enzyme as an important virulence factor in cell line cultures. SlpE is found in our clinical isolated RM66262 and the majority of clinical isolates, but it is absent from most non-clinical isolates, including the reference S. marcescens strain Db11. However, little is known about environmental signals and regulatory factors that modulate its production. In this work, we have assessed the regulation of SlpE using a gfp-containing reporter plasmid. Results showed that SlpE expression is induced during the stationary growth phase, although its expression levels are five times lower than of the major protease PrtA at 30ºC. One defense of the vertebrate hosts against bacterial infection is the nutrient deprivation to prevent bacterial growth in a process termed nutritional immunity. The most significant form of nutritional immunity is the sequestration of iron. We found that under iron-depleted conditions, the transcription levels of PslpE-gfp is five times higher than in iron-suppled medium, reaching levels equivalent to prtA expression at 30ºC. In addition, we show that this increase in the expression levels of SlpE is Ferric Uptake Regulator (Fur)-dependent. By immunofluorescence analysis, we also show that, in contrast to PrtA, the expression levels of SlpE are induced upon Serratia invasion to epithelial cells. These results suggest that S. marcescens SlpE would be involved in proteolytic activity under iron-limiting conditions within the host intracellular niche.