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Microbiology. 2010 Jun;156(Pt 6):1719-29. doi: 10.1099/mic.0.037069-0. Epub 2010 Mar 11.

A heterodimer of EsxA and EsxB is involved in sporulation and is secreted by a type VII secretion system in Streptomyces coelicolor.

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  • 1Institute of Life Science, School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.

Abstract

An esx locus, related to the multiple esx loci of Mycobacterium tuberculosis, is conserved in all sequenced Streptomyces genomes, where it is associated with the developmental regulatory gene bldB. Here we demonstrate that the esxBA operon, comprising part of the locus, has a novel morphogenetic function in the model species Streptomyces coelicolor. This operon encodes two proteins belonging to the WXG-100 superfamily that can form a heterodimer and are secreted in the absence of signal sequences. A mutation in esxBA results in a delay in sporulation, with eventual development of aerial hyphae with chains of abnormally sized spore compartments possessing irregular DNA contents. During early sporulation, expression of the operon is elevated in a bldB mutant. Other genes in the locus, notably SCO5734 and SCO5721, encode components of a type VII secretion system. Disruption of either of these genes prevents secretion of EsxAB but has no effect on sporulation. To explain the morphogenetic function of EsxAB, we propose that the heterodimer sequesters a regulator of expression of genes involved in nucleoid organization during sporulation.

PMID:
20223806
[PubMed - indexed for MEDLINE]
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