REGULATION OF LpxO1 AND LpxO2 AND ITS INVOLVEMENT IN POLYMYXIN B RESISTANCE IN Serratia marcescens

JAVIER FERNANDO MARISCOTTI; ELEONORA GARCÍA VÉSCOVI

Mar del Plata

Congreso; LI Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2015

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular - SAIB

The lipopolysaccharide (LPS) lipid A is recognized by the innate system. The gram-negative bacteria modify the LPS to avoid host immune system and to resist killing by antimicrobial peptide. Serratia marcescens is an enteric bacterium that can function as an opportunistic pathogen within immunocompromised hosts. This pathogenic bacterium possesses several pathogenic factors, including adhesins, cell surface hydrophobicity, extracellular enzymes and LPS. S. marcescens strain RM66262 contains two putative lpxO genes homologues (lpxO1 and lpxO2). LpxO is an oxygenase that 2-hydroxylates specific acyl chains in the lipid A. In this work, we analyzed the regulation of lpxO1 and lpxO2 and its involvement in antimicrobial peptide resistance. We construct lpxO1 and lpxO2 mutants in S. marcescens and determined their resistance to the polymyxin B. The results show that LpxO1 is necessary for polymyxin B resistance while LpxO2 is dispensable. In a large number of bacterial species, the modifications in the LPS that confer resistance to antimicrobial peptides are regulated by the PhoPQ system. Furthermore, in Klebsiella pneumoniae RamA, a transcriptional regulator, functions as an alternate regulator of certain lipid A biosynthesis genes. Bioinformatics analyses revealed consensus sequence for the recognition of the response regulator PhoP in the lpxO1 promoter. The contribution of PhoP and RamA in the expression level of lpxO1 and lpxO2 was analyzed by RT-PCR. Our preliminary results show that PhoP and RamA are involved in the lpxO1 and lpxO2 regulation.