Characterization of legiolysin (<i>lly</i>), responsible for haemolytic activity, colour production and fluorescence of <i>Legionella pneumophila</i>

Wintermeyer, Eva; Rdest, Ursula; Ludwig, Birgit; Debes, Anetie; Hacker, Jörg

doi:10.1111/j.1365-2958.1991.tb01886.x

Cited by 46 publications

(49 citation statements)

References 51 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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“…Detection of 3-hydroxy-C6-HSL and C6-HSL was done by overlaying the TLC plates with soft top agar seeded with the Chromobacterium violaceum CV026 reporter using both the AHL activation and inhibition violacein assays (34). For the detection of 3-oxo-C10-HSL, a bioluminescent E. coli lux-based AHL biosensor termed E. coli JM109(pSB1075), which contains an intact lasR gene and the lasI promoter from Pseudomonas aeruginosa fused to luxCDABE from Photorhabdus luminescens, was used (70).…”

Section: Methodsmentioning

confidence: 99%

VanT, a Homologue of Vibrio harveyi LuxR, Regulates Serine, Metalloprotease, Pigment, and Biofilm Production in Vibrio anguillarum

et al. 2002

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Vibrio anguillarum possesses at least two N-acylhomoserine lactone (AHL) quorum-sensing circuits, one of which is related to the luxMN system of Vibrio harveyi. In this study, we have cloned an additional gene of this circuit, vanT, encoding a V. harveyi LuxR-like transcriptional regulator. A V. anguillarum ⌬vanT null mutation resulted in a significant decrease in total protease activity due to loss of expression of the metalloprotease EmpA, but no changes in either AHL production or virulence. Additional genes positively regulated by VanT were identified from a plasmid-based gene library fused to a promoterless lacZ. Three lacZ fusions (serA::lacZ, hpdA-hgdA::lacZ, and sat-vps73::lacZ) were identified which exhibited decreased expression in the ⌬vanT strain. SerA is similar to 3-phosphoglycerate dehydrogenases and catalyzes the first step in the serine-glycine biosynthesis pathway. HgdA has identity with homogentisate dioxygenases, and HpdA is homologous to 4-hydroxyphenylpyruvate dioxygenases (HPPDs) involved in pigment production. V. anguillarum strains require an active VanT to produce high levels of an L-tyrosine-induced brown color via HPPD, suggesting that VanT controls pigment production. Vps73 and Sat are related to Vibrio cholerae proteins encoded within a DNA locus required for biofilm formation. A V. anguillarum ⌬vanT mutant and a mutant carrying a polar mutation in the sat-vps73 DNA locus were shown to produce defective biofilms. Hence, a new member of the V. harveyi LuxR transcriptional activator family has been characterized in V. anguillarum that positively regulates serine, metalloprotease, pigment, and biofilm production.

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“…Additionally, the icm/ dot genes mediate cytotoxic events such as (i) contactdependent immediate cytotoxicity due to pore formation (Kirby et al, 1998;Zuckman et al, 1999), (ii) induction of apoptosis (Zink et al, 2002), and (iii) egress of the bacteria from the vacuole of the spent host cell (Molmeret et al, 2002). Other cytotoxic factors of L. pneumophila include legiolysin (Wintermeyer et al, 1991), the zinc metalloprotease Msp (Quinn & Tompkins, 1989;Szeto & Shuman, 1990), and RtxA, a member of the RTX (repeats in toxin) family of cytotoxic adhesins (Cirillo et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

The amoebae plate test implicates a paralogue of lpxB in the interaction of Legionella pneumophila with Acanthamoeba castellanii

et al. 2005

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Legionella pneumophila is a bacterial parasite of freshwater amoebae which also grows in alveolar macrophages and thus causes the potentially fatal pneumonia Legionnaires' disease. Intracellular growth within amoebae and macrophages is mechanistically similar and requires the Icm/Dot type IV secretion system. This paper reports the development of an assay, the amoebae plate test (APT), to analyse growth of L. pneumophila wild-type and icm/dot mutant strains spotted on agar plates in the presence of Acanthamoeba castellanii. In the APT, wild-type L. pneumophila formed robust colonies even at high dilutions, icmT, -R, -P or dotB mutants failed to grow, and icmS or -G mutants were partially growth defective. The icmS or icmG mutant strains were used to screen an L. pneumophila chromosomal library for genes that suppress the growth defect in the presence of the amoebae. An icmS suppressor plasmid was isolated that harboured the icmS and flanking icm genes, indicating that this plasmid complements the intracellular growth defect of the mutant. In contrast, different icmG suppressor plasmids rendered the icmG mutant more cytotoxic for A. castellanii without enhancing intracellular multiplication in amoebae or RAW264.7 macrophages. Deletion of individual genes in the suppressor plasmids inserts identified lcs (Legionella cytotoxic suppressor) -A, -B, -C and -D as being required for enhanced cytotoxicity of an icmG mutant strain. The corresponding proteins show sequence similarity to hydrolases, NlpD-related metalloproteases, lipid A disaccharide synthases and ABC transporters, respectively. Overexpression of LcsC, a putative paralogue of the lipid A disaccharide synthase LpxB, increased cytotoxicity of an icmG mutant but not that of other icm/dot or rpoS mutant strains against A. castellanii. Based on sequence comparison and chromosomal location, lcsB and lcsC probably encode enzymes involved in cell wall maintenance and peptidoglycan metabolism. The APT established here may prove useful to identify other bacterial factors relevant for interactions with amoeba hosts.

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Characterization of legiolysin (lly), responsible for haemolytic activity, colour production and fluorescence of Legionella pneumophila

Cited by 46 publications

References 51 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

VanT, a Homologue of Vibrio harveyi LuxR, Regulates Serine, Metalloprotease, Pigment, and Biofilm Production in Vibrio anguillarum

The amoebae plate test implicates a paralogue of lpxB in the interaction of Legionella pneumophila with Acanthamoeba castellanii

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