Mutagenesis of Legionella pneumophila using Jn903 dllIacZ: identification of a growth‐phase‐regulated pigmentation gene

Wiater, Lawrence A.; Sadosky, Alesia; Shuman, Howard A.

doi:10.1111/j.1365-2958.1994.tb00343.x

Cited by 96 publications

(100 citation statements)

References 31 publications

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“…Pigment production requires at least two distinct genetic loci, named pig and lly. The lly gene product, legiolysin, catalyzes the formation of homogentisic acid, which likely polymerizes to form a melaninlike pigment (37,38). Although not required for intracellular growth (35), pigment accumulation and the efficiency of macrophage infection by L. pneumophila are correlated genetically.…”

Section: Discussionmentioning

confidence: 99%

The LetE Protein Enhances Expression of Multiple LetA/LetS-Dependent Transmission Traits by Legionella pneumophila

Bachman

Swanson

2004

Infect Immun

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Legionella pneumophila colonizes freshwater amoebae and can also replicate within alveolar macrophages. When their nutrient supply is exhausted, replicating bacteria become cytotoxic, motile, and infectious, which is thought to promote transmission to a new amoeba. The differentiation of L. pneumophila is coordinated by the sigma factors RpoS and FliA and the two-component regulator LetA/LetS and is enhanced by the letE locus. Here we demonstrate that letE promotes motility by increasing expression of the flagellin gene flaA but has little impact on the transcription of fliA, the flagellar sigma factor gene. In addition to promoting motility, letE induces the characteristic shape, pigment, and heat resistance of stationary-phase L. pneumophila. To gain insight into how letE promotes the expression of the transmission phenotype, we designed molecular genetic experiments to discriminate between the following three models: letE mutations are polar on milX; letE encodes a small novel protein; or, by analogy to csrB, letE encodes a regulatory RNA that sequesters CsrA to relieve repression. We report that letE encodes an activator protein, as it does not complement an Escherichia coli csrB mutant, it directs the synthesis of an ϳ12-kDa polypeptide, and a letE nonsense mutation eliminates function. A monocistronic letE RNA is abundant during the exponential phase, and its decay during the stationary phase requires RpoS and LetA/LetS. We also discuss how the LetE protein may interact with LetA/LetS and CsrA to enhance L. pneumophila differentiation to a transmissible form.

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Section: Discussionmentioning

confidence: 99%

The LetE Protein Enhances Expression of Multiple LetA/LetS-Dependent Transmission Traits by Legionella pneumophila

Bachman

Swanson

2004

Infect Immun

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“…Legionella proliferation in macrophages and in D. discoideum relies on the pathogen avoiding the endolysosomal pathway, which it does by inhibiting fusion of the phagosome with lysosomes (Roy et al, 1998;Wiater et al, 1994;Solomon et al, 2000). However, an integrated view of the signalling pathways and interactions between Legionella proteins and host proteins during Legionella pathogenesis is yet to be established.…”

Section: Dmmbiologistsorg 484mentioning

confidence: 99%

Legionella pneumophilamultiplication is enhanced by chronic AMPK signalling in mitochondrially diseased Dictyostelium cells

Francione

Smith

Accari

et al. 2009

Disease Models &Amp; Mechanisms

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SUMMARYHuman patients with mitochondrial diseases are more susceptible to bacterial infections, particularly of the respiratory tract. To investigate the susceptibility of mitochondrially diseased cells to an intracellular bacterial respiratory pathogen, we exploited the advantages of Dictyostelium discoideum as an established model for mitochondrial disease and for Legionella pneumophila pathogenesis. Legionella infection of macrophages involves recruitment of mitochondria to the Legionella-containing phagosome. We confirm here that this also occurs in Dictyostelium and investigate the effect of mitochondrial dysfunction on host cell susceptibility to Legionella. In mitochondrially diseased Dictyostelium strains, the pathogen was taken up at normal rates, but it grew faster and reached counts that were twofold higher than in the wild-type host. We reported previously that other mitochondrial disease phenotypes for Dictyostelium are the result of the activity of an energy-sensing cellular alarm protein, AMP-activated protein kinase (AMPK). Here, we show that the increased ability of mitochondrially diseased cells to support Legionella proliferation is suppressed by antisense-inhibiting expression of the catalytic AMPKα subunit. Conversely, mitochondrial dysfunction is phenocopied, and intracellular Legionella growth is enhanced, by overexpressing an active form of AMPKα in otherwise normal cells. These results indicate that AMPK signalling in response to mitochondrial dysfunction enhances Legionella proliferation in host cells.

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“…For E/PE sample preparation, L. pneumophila was grown in broth until E or PE and enrichment of flagellin FliC (also designated FlaA in some studies) was used to confirm entry into PE (12,63,64) (Fig. 1A and 1B).…”

Section: Overview Of L Pneumophila E and Pe Proteomes-be-mentioning

confidence: 99%

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

Auraß

Gerlach

Becher

et al. 2016

Molecular & Cellular Proteomics

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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 phasespecific 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 lifestage specific markers for pathogen analysis. Molecular

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Mutagenesis of Legionella pneumophila using Jn903 dllIacZ: identification of a growth‐phase‐regulated pigmentation gene

Cited by 96 publications

References 31 publications

The LetE Protein Enhances Expression of Multiple LetA/LetS-Dependent Transmission Traits by Legionella pneumophila

The LetE Protein Enhances Expression of Multiple LetA/LetS-Dependent Transmission Traits by Legionella pneumophila

Legionella pneumophilamultiplication is enhanced by chronic AMPK signalling in mitochondrially diseased Dictyostelium cells

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

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