Insight into the roles of exoproteins in the biology of pathogenic Leptospira

ESHGHI A, HESTER S, THOMAS B, PRÊTRE G AND PICARDEAU M

Paris

Conferencia; Microbiology after the genomics revolution: Genomes 2014; 2014

EMBO Conference

Extracellular and outer membrane proteins are the medium through which cells interact with their surrounding environment. For bacteria, extracellular proteins play a broad spectrum of roles from nutrient acquisition and cell-celcommunication to modification of and interaction with host factors. Pathogenic Leptospira are zoonotic bacteria with worldwide prevalence and manifest the disease known as leptospirosis. Our aim in this study was to perform quantitative proteomics on exoproteins to both identify and measure the quantities of exoproteins from Leptospira cultured under various in vitro conditions, to assess the requirement of select exoprotein encoding genes for virulence in the Mongolian gerbil infection model and to use this proteomic data to gain insight into protein export in Leptospira. We performed label-free SINQ normalized spectral index quantitative mass spectrometry on the whole cell and exoproteins of Leptospira cultured under standard in vitro conditions (30°C), cultured at physiological temperature (37°C) and cultured at physiological NaCl concentration (120 mM). Immunoblot experiments using acute phase sera demonstrated expression of numerous exoproteins during the infection process. Using a random transposon insertion library of leptospiral mutants, we selected 10 mutants disrupted in exoprotein encoding genes to ascertain virulence in the gerbil infection model. Lastly, we used an in silico approach to analyse the N-terminal region of 43 exoproteins with the aim of identifying a consensus sequence that may be used by Leptospira, and potentially other bacteria, for protein transport to the extracellular.