Abstract

Serratia sp. ATCC 39006 (S39006) is a Gram-negative bacterium virulent in plant (potato) and animal (Caenorhabditis elegans) models. It produces two secondary metabolite antibiotics, prodigiosin and a carbapenem, and the exoenzymes, pectate lyase and cellulase. A complex regulatory network controls production of prodigiosin, including a quorum sensing (QS) system, and we hypothesize that Hfq-dependent small regulatory RNAs might also play a role. Hfq is an RNA chaperone involved in post-transcriptional regulation that plays a key role in stress response and virulence in other bacterial species. We constructed an S39006 ∆hfq mutant and showed that production of prodigiosin and carbapenem was abolished, while production of the QS molecule, butanoyl homoserine lactone (BHL), was unaffected. Using transcriptional fusions, we found that Hfq regulates the QS response regulators, SmaR and CarR. Additionally, exoenzyme production and swimming motility are decreased in ∆hfq, and virulence is attenuated in potato and C. elegans. We are currently analysing the whole transcriptome of S39006 WT and ∆hfq, sequenced by RNA -seq, in order to define the complete regulon of Hfq. This study confirms a role for Hfq in pathogenesis and the regulation of secondary metabolite production in S39006 , increasing further the complexity of the currently described regulatory network.