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Mol Cell Proteomics. 2016 Jan;15(1):177-200. doi: 10.1074/mcp.M115.053579. Epub 2015 Nov 6.

Life Stage-specific Proteomes of Legionella pneumophila Reveal a Highly Differential Abundance of Virulence-associated Dot/Icm effectors.

Author information

1
From the ‡Robert Koch-Institut, Wernigerode Branch, Division of Enteropathogenic Bacteria and Legionella (FG11), Burgstr. 37, 38855 Wernigerode, Germany;
2
§Institute for Microbiology, Ernst-Moritz-Arndt University Greifswald, Friedrich-Ludwig-Jahn-Str. 15, 17487 Greifswald, Germany.
3
From the ‡Robert Koch-Institut, Wernigerode Branch, Division of Enteropathogenic Bacteria and Legionella (FG11), Burgstr. 37, 38855 Wernigerode, Germany; fliegera@rki.de.

Abstract

Major differences in the transcriptional program underlying the phenotypic switch between exponential and post-exponential growth of Legionella pneumophila were formerly described characterizing important alterations in infection capacity. Additionally, a third state is known where the bacteria transform in a viable but nonculturable state under stress, such as starvation. We here describe phase-related proteomic changes in exponential phase (E), postexponential phase (PE) bacteria, and unculturable microcosms (UNC) containing viable but nonculturable state cells, and identify phase-specific proteins. We present data on different bacterial subproteomes of E and PE, such as soluble whole cell proteins, outer membrane-associated proteins, and extracellular proteins. In total, 1368 different proteins were identified, 922 were quantified and 397 showed differential abundance in E/PE. The quantified subproteomes of soluble whole cell proteins, outer membrane-associated proteins, and extracellular proteins; 841, 55, and 77 proteins, respectively, were visualized in Voronoi treemaps. 95 proteins were quantified exclusively in E, such as cell division proteins MreC, FtsN, FtsA, and ZipA; 33 exclusively in PE, such as motility-related proteins of flagellum biogenesis FlgE, FlgK, and FliA; and 9 exclusively in unculturable microcosms soluble whole cell proteins, such as hypothetical, as well as transport/binding-, and metabolism-related proteins. A high frequency of differentially abundant or phase-exclusive proteins was observed among the 91 quantified effectors of the major virulence-associated protein secretion system Dot/Icm (> 60%). 24 were E-exclusive, such as LepA/B, YlfA, MavG, Lpg2271, and 13 were PE-exclusive, such as RalF, VipD, Lem10. The growth phase-related specific abundance of a subset of Dot/Icm virulence effectors was confirmed by means of Western blotting. We therefore conclude that many effectors are predominantly abundant at either E or PE which suggests their phase specific function. The distinct temporal or spatial presence of such proteins might have important implications for functional assignments in the future or for use as life-stage specific markers for pathogen analysis.

PMID:
26545400
PMCID:
PMC4762515
DOI:
10.1074/mcp.M115.053579
[Indexed for MEDLINE]
Free PMC Article

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