Surface Translocation by<i>Legionella pneumophila</i>: a Form of Sliding Motility That Is Dependent upon Type II Protein Secretion

Stewart, Catherine R.; Rossier, Ombeline; Cianciotto, Nicholas P.

doi:10.1128/jb.01531-08

Cited by 59 publications

(85 citation statements)

References 123 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Sliding or spreading by expansion has been described for a diverse group of bacteria, such as mycobacteria, Bacillus subtilis, Vibrio cholerae, Serratia marcescens, Pseudomonas aeruginosa, and Legionella pneumophila (1,5,9,27,31,43), in which a strong correlation between sliding and the production of surfactants has been established. For example, the production of rhamnolipids in Pseudomonas, the lipopeptides surfactin and serrawettin in Bacillus and Serratia, respectively, or a surfactant-like material in Legionella facilitates flagellum-independent surface translocation in these bacteria.…”

Section: Discussionmentioning

confidence: 99%

ExpR Is Not Required for Swarming but Promotes Sliding in Sinorhizobium meliloti

et al. 2012

View full text Add to dashboard Cite

Swarming is a mode of translocation dependent on flagellar activity that allows bacteria to move rapidly across surfaces. In several bacteria, swarming is a phenotype regulated by quorum sensing. It has been reported that the swarming ability of the soil bacterium Sinorhizobium meliloti Rm2011 requires a functional ExpR/Sin quorum-sensing system. However, our previous published results demonstrate that strains Rm1021 and Rm2011, both known to have a disrupted copy of expR, are able to swarm on semisolid minimal medium. In order to clarify these contradictory results, the role played by the LuxR-type regulator ExpR has been reexamined. Results obtained in this work revealed that S. meliloti can move over semisolid surfaces using at least two different types of motility. One type is flagellum-independent surface spreading or sliding, which is positively influenced by a functional expR gene mainly through the production of exopolysaccharide II (EPS II). To a lesser extent, EPS II-deficient strains can also slide on surfaces by a mechanism that is at least dependent on the siderophore rhizobactin 1021. The second type of surface translocation shown by S. meliloti is swarming, which is greatly dependent on flagella and rhizobactin 1021 but does not require ExpR. We have extended our study to demonstrate that the production of normal amounts of succinoglycan (EPS I) does not play a relevant role in surface translocation but that its overproduction facilitates both swarming and sliding motilities.

show abstract

Section: Discussionmentioning

confidence: 99%

ExpR Is Not Required for Swarming but Promotes Sliding in Sinorhizobium meliloti

et al. 2012

View full text Add to dashboard Cite

show abstract

“…L. pneumophila strain 130b (ATCC BAA-74, also known as AA100) is a clinical isolate that served as our WT and parental strain for mutants (90). Both mutant strain NU275, which lacks a functional lspF gene that encodes an inner membrane component of the T2S apparatus, and mutant strain NU347, which lacks a functional flaA gene encoding flagellin, were described previously (18,91). A mutant lacking both flaA and lspF (NU430) was obtained by introducing pGlspF::Km (18) into NU347 by transformation (91) and then selecting for the acquisition of kanamycin resistance.…”

Section: Methodsmentioning

confidence: 99%

“…Both mutant strain NU275, which lacks a functional lspF gene that encodes an inner membrane component of the T2S apparatus, and mutant strain NU347, which lacks a functional flaA gene encoding flagellin, were described previously (18,91). A mutant lacking both flaA and lspF (NU430) was obtained by introducing pGlspF::Km (18) into NU347 by transformation (91) and then selecting for the acquisition of kanamycin resistance. In order to help monitor the behavior of L. pneumophila in macrophages, we utilized previously reported L. pneumophila WT and T2S mutant strains with a GFP-expressing plasmid introduced (19).…”

Section: Methodsmentioning

confidence: 99%

The Type II Secretion System of Legionella pneumophila Dampens the MyD88 and Toll-Like Receptor 2 Signaling Pathway in Infected Human Macrophages

2017

Self Cite

View full text Add to dashboard Cite

Previously, we reported that mutants of Legionella pneumophila lacking a type II secretion (T2S) system elicit higher levels of cytokines (e.g., interleukin-6 [IL-6]) following infection of U937 cells, a human macrophage-like cell line. We now show that this effect of T2S is also manifest upon infection of human THP-1 macrophages and peripheral blood monocytes but does not occur during infection of murine macrophages. Supporting the hypothesis that T2S acts to dampen the triggering of an innate immune response, we observed that the mitogen-activated protein kinase (MAPK) and nuclear transcription factor kappa B (NF-B) pathways are more highly stimulated upon infection with the T2S mutant than upon infection with the wild type. By using short hairpin RNA to deplete proteins involved in specific pathogen-associated molecular pattern (PAMP) recognition pathways, we determined that the dampening effect of the T2S system was not dependent on nucleotide binding oligomerization domain (NOD)-like receptors (NLRs), retinoic acid-inducible protein I (RIG-I)-like receptors (RLRs), double-stranded RNA (dsRNA)-dependent protein kinase receptor (PKR), or TIR domain-containing adaptor inducing interferon beta (TRIF) signaling or an apoptosis-associated speck-like protein containing a CARD (ASC)-or caspase-4-dependent inflammasome. However, the dampening effect of T2S on IL-6 production was significantly reduced upon gene knockdown of myeloid differentiation primary response 88 (MyD88), TANK binding kinase 1 (TBK1), or Toll-like receptor 2 (TLR2). These data indicate that the L. pneumophila T2S system dampens the signaling of the TLR2 pathway in infected human macrophages. We also document the importance of PKR, TRIF, and TBK1 in cytokine secretion during L. pneumophila infection of macrophages.KEYWORDS Legionella pneumophila, TLR2, cytokine, innate immunity, macrophage, type II secretion L egionella pneumophila, a Gram-negative bacterium that is widespread in aquatic habitats, is the principal agent of Legionnaires' disease pneumonia (1-6). In the lungs, Legionella bacteria invade and grow in resident macrophages and then trigger severe inflammation (2). In macrophages, L. pneumophila evades the degradative lysosomal pathway and replicates to large numbers within a membrane-bound vacuole, the Legionella-containing vacuole (LCV) (7,8). Two protein secretion systems, Lsp type II secretion (T2S) and Dot/Icm type IV secretion (T4S), play major roles in the pathogenesis of L. pneumophila (9, 10). In T2S, protein substrates are first translocated across the inner membrane, and upon the action of the T2S pilus-like apparatus, they then exit the bacterial cell through a specific outer membrane pore (11). Using proteomics and enzymatic assays, we have shown that the T2S system of L. pneumo-

show abstract

“…The result was a plasmid (pUClbtUK) carrying lbtU with a Km r insertion circa halfway through the gene's coding region. pUClbtUK was introduced into 130b by transformation (3,114,124), and transformants were selected on antibiotic-containing BCYE agar. Insertion of Km r into the chromosomal lbtU gene was confirmed by PCR using CC01 and CC02.…”

Section: Methodsmentioning

confidence: 99%

Legionella pneumophila LbtU Acts as a Novel, TonB-Independent Receptor for the Legiobactin Siderophore

et al. 2011

Self Cite

View full text Add to dashboard Cite

Gram-negative Legionella pneumophila produces a siderophore (legiobactin) that promotes lung infection. We previously determined that lbtA and lbtB are required for the synthesis and secretion of legiobactin. DNA sequence and reverse transcription-PCR (RT-PCR) analyses now reveal the presence of an iron-repressed gene (lbtU) directly upstream of the lbtAB-containing operon. In silico analysis predicted that LbtU is an outer membrane protein consisting of a 16-stranded transmembrane ␤-barrel, multiple extracellular domains, and short periplasmic tails. Immunoblot analysis of cell fractions confirmed an outer membrane location for LbtU. Although replicating normally in standard media, lbtU mutants, like lbtA mutants, were impaired for growth on iron-depleted agar media. While producing typical levels of legiobactin, lbtU mutants were unable to use supplied legiobactin to stimulate growth on iron-depleted media and displayed an inability to take up iron. Complemented lbtU mutants behaved as the wild type did. The lbtU mutants were also impaired for infection in a legiobactin-dependent manner. Together, these data indicate that LbtU is involved in the uptake of legiobactin and, based upon its location, is most likely the Legionella siderophore receptor. The sequence and predicted two-dimensional (2D) and 3D structures of LbtU were distinct from those of all known siderophore receptors, which generally contain a 22-stranded ␤-barrel and an extended N terminus that binds TonB in order to transduce energy from the inner membrane. This observation coupled with the fact that L. pneumophila does not encode TonB suggests that LbtU is a new type of receptor that participates in a form of iron uptake that is mechanistically distinct from the existing paradigm.

show abstract

Surface Translocation byLegionella pneumophila: a Form of Sliding Motility That Is Dependent upon Type II Protein Secretion

Cited by 59 publications

References 123 publications

ExpR Is Not Required for Swarming but Promotes Sliding in Sinorhizobium meliloti

ExpR Is Not Required for Swarming but Promotes Sliding in Sinorhizobium meliloti

The Type II Secretion System of Legionella pneumophila Dampens the MyD88 and Toll-Like Receptor 2 Signaling Pathway in Infected Human Macrophages

Legionella pneumophila LbtU Acts as a Novel, TonB-Independent Receptor for the Legiobactin Siderophore

Contact Info

Product

Resources

About