ROLE OF POLY‐GAMMA-GLUTAMIC ACID SYNTHESIS LOCUS IN FRANCISELLA MICROBIAL PHYSIOLOGY

Abstract

Francisella tularensis is the causative agent of tularemia. It is a facultative intracellular bacterium and part of its life cycle outside of a eukaryotic host. Poly-gamma glutamic acid (γ- PGA) is produced via the genes in the pgs locus. γ-PGA is one of the major virulence and survival factors of B. anthracis and enables S. epidermidis to escape phagocytosis. It is common for gram-positive bacteria to produce an attached γ-PGA capsule, but it is unknown for gram-negative bacteria. Due to the presence of the outer membrane, the mechanism for attaching this type of capsule to the bacteria in gram-negative bacteria is not possible. However, all strains of Francisella require this locus for virulence. The physiological role of pgs (cap) locus in Francisella is unclear but the deletion of these genes had a significant effect on intracellular growth and resulted in an attenuated mutant strain. Characterizing the potential formation of γ-PGA when Francisella is under stress is important in understanding the resistance to stress and the ability to grow in harsh environments. The goals of this study are to characterize this pgs locus and identify the ability of this operon to produce γ-PGA.