The Francisella pathogenicity island protein IglA localizes to the bacterial cytoplasm and is needed for intracellular growth
Date
2007-01-17
Authors
de Bruin, Olle M
Ludu, Jagjit S
Nano, Francis E
Journal Title
Journal ISSN
Volume Title
Publisher
BioMed Central
Abstract
Background: Francisella tularensis is a gram negative, facultative intracellular bacterium that is the
etiological agent of tularemia. F. novicida is closely related to F. tularensis but has low virulence for
humans while being highly virulent in mice. IglA is a 21 kDa protein encoded by a gene that is part
of an iglABCD operon located on the Francisella pathogenicity island (FPI).
Results: Bioinformatics analysis of the FPI suggests that IglA and IglB are components of a newly
described type VI secretion system. In this study, we showed that IglA regulation is controlled by
the global regulators MglA and MglB. During intracellular growth IglA production reaches a
maximum at about 10 hours post infection. Biochemical fractionation showed that IglA is a soluble
cytoplasmic protein and immunoprecipitation experiments demonstrate that it interacts with the
downstream-encoded IglB. When the iglB gene was disrupted IglA could not be detected in cell
extracts of F. novicida, although IglC could be detected. We further demonstrated that IglA is
needed for intracellular growth of F. novicida. A non-polar iglA deletion mutant was defective for
growth in mouse macrophage-like cells, and in cis complementation largely restored the wild type
macrophage growth phenotype.
Conclusion: The results of this study demonstrate that IglA and IglB are interacting cytoplasmic
proteins that are required for intramacrophage growth. The significance of the interaction may be
to secrete effector molecules that affect host cell processes.
Description
BioMed Central
Keywords
Citation
de Bruin OM, Ludu JS, Nano FE. The Francisella pathogenicity island protein IglA localizes to the bacterial cytoplasm and is needed for intracellular growth. BMC Microbiol. 2007 Jan 17;7:1. doi:10.1186/1471-2180-7-1