Caister Academic Press

Iron Uptake in Francisella

Girija Ramakrishnan
from: Iron Uptake and Homeostasis in Microorganisms (Edited by: Pierre Cornelis and Simon C. Andrews). Caister Academic Press, U.K. (2010)

Abstract

Francisella tularensis is unusual among Gram-negative bacteria in that its genome does not encode orthologs for TonB, ExbB and ExbD that typically energize the uptake of iron across the outer membrane. This organism secretes however a siderophore similar in structure to rhizoferrin. The fsl operon of six genes encodes functions for biosynthesis and uptake of the siderophore. Two of these genes encode a siderophore synthetase belonging to the nonribosomal peptide synthetase (NRPS)-independent synthetase (NIS)-family and a protein belonging to the pyridoxyl phosphate-dependent decarboxylase family, and both are required for siderophore production. Siderophore utilization involves the product of the fslE gene, a protein unique to Francisella species that could function as a siderophore receptor. Additionally, genes related in sequence to fslE also play a role in siderophore acquisition. The mechanism for TonB-independent iron uptake in this microorganism remains to be elucidated read more ...
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