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1.
Although many bacteria are known to be naturally competent for DNA uptake, this ability varies dramatically between species and even within a single species, some isolates display high levels of competence while others seem to be completely nontransformable. Surprisingly, many nontransformable bacterial strains appear to encode components necessary for DNA uptake. We believe that many such strains are actually competent but that this ability has been overlooked because standard laboratory conditions are inappropriate for competence induction. For example, most strains of the gram-negative bacterium Legionella pneumophila are not competent under normal laboratory conditions of aerobic growth at 37 degrees C. However, it was previously reported that microaerophilic growth at 37 degrees C allows L. pneumophila serogroup 1 strain AA100 to be naturally transformed. Here we report that another L. pneumophila serogroup 1 strain, Lp02, can also be transformed under these conditions. Moreover, Lp02 can be induced to high levels of competence by a second set of conditions, aerobic growth at 30 degrees C. In contrast to Lp02, AA100 is only minimally transformable at 30 degrees C, indicating that Lp02 is hypercompetent under these conditions. To identify potential causes of hypercompetence, we isolated mutants of AA100 that exhibited enhanced DNA uptake. Characterization of these mutants revealed two genes, proQ and comR, that are involved in regulating competence in L. pneumophila. This approach, involving the isolation of hypercompetent mutants, shows great promise as a method for identifying natural transformation in bacterial species previously thought to be nontransformable. 相似文献
2.
《Biochemical and biophysical research communications》2020,521(3):799-805
Lpg0189 is a type II secretion system-dependent extracellular protein with unknown function from Legionella pneumophila. Herein, we determined the crystal structure of Lpg0189 at 1.98 Å resolution by using single-wavelength anomalous diffraction (SAD). Lpg0189 folds into a novel chair-shaped architecture, with two sheets roughly perpendicular to each other. Bioinformatics analysis suggests Lpg0189 and its homologues are unique to Legionellales and evolved divergently. The interlinking structural and bioinformatics studies provide a better understanding of this hypothetical protein. 相似文献
3.
D. A. Cunliffe 《Journal of applied microbiology》1990,68(5):453-459
Chloramination which is used in South Australia to control the growth of Naegleria fowleri , was investigated to see if it would also control that of Legionella pneumophila . It was found that L. pneumophila was more sensitive than Escherichia coli to monochloramine. At 1.0 mg/l, a 99% kill of L. pneumophila was achieved in 15 min compared with 37 min for a 99% kill of E. coli. Combined with the stability of monochloramine, even at elevated temperatures, the results suggest that this disinfectant would control the growth of L. pneumophila in water distribution systems. 相似文献
4.
D A Cunliffe 《The Journal of applied bacteriology》1990,68(5):453-459
Chloramination which is used in South Australia to control the growth of Naegleria fowleri, was investigated to see if it would also control that of Legionella pneumophila. It was found that L. pneumophila was more sensitive than Escherichia coli to monochloramine. At 1.0 mg/l, a 99% kill of L. pneumophila was achieved in 15 min compared with 37 min for a 99% kill of E. coli. Combined with the stability of monochloramine, even at elevated temperatures, the results suggest that this disinfectant would control the growth of L. pneumophila in water distribution systems. 相似文献
5.
6.
Flieger A Gong S Faigle M Stevanovic S Cianciotto NP Neumeister B 《Journal of bacteriology》2001,183(6):2121-2124
We show that Legionella pneumophila possesses lysophospholipase A activity, which releases fatty acids from lysophosphatidylcholine. The NH2-terminal sequence of the enzyme contained FGDSLS, corresponding to a catalytic domain in a recently described group of lipolytic enzymes. Culture supernatants of a L. pneumophila pilD mutant lost the ability to cleave lysophosphatidylcholine. 相似文献
7.
Evidence for pore-forming ability by Legionella pneumophila 总被引:10,自引:5,他引:10
James E. Kirby Joseph P. Vogel Helene L. Andrews & Ralph R. Isberg 《Molecular microbiology》1998,27(2):323-336
Legionella pneumophila is the cause of Legionnaires' pneumonia. After internalization by macrophages, it bypasses the normal endocytic pathway and occupies a replicative phagosome bound by endoplasmic reticulum. Here, we show that lysis of macrophages and red blood cells by L . pneumophila was dependent on dotA and other loci known to be required for proper targeting of the phagosome and replication within the host cell. Cytotoxicity occurred rapidly during a high-multiplicity infection, required close association of the bacteria with the eukaryotic cell and was a form of necrotic cell death accompanied by osmotic lysis. The differential cytoprotective ability of high-molecular-weight polyethylene glycols suggested that osmotic lysis resulted from insertion of a pore less than 3 nm in diameter into the plasma membrane. Results concerning the uptake of membrane-impermeant fluorescent compounds of various sizes are consistent with the osmoprotection analysis. Therefore, kinetic and genetic evidence suggested that the apparent ability of L . pneumophila to insert a pore into eukaryotic membranes on initial contact may play a role in altering endocytic trafficking events within the host cell and in the establishment of a replicative vacuole. 相似文献
8.
Legionella pneumophila has become a paradigm for facultative intracellular pathogens that modulate biogenesis of their phagosomes into replicative niches. The ability to alter host cell biology and tailor it into a hospitable host for intracellular proliferation is at the crux of the mechanism of pathogenesis of Legionnaires' disease. 相似文献
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10.
Temmerman R Vervaeren H Noseda B Boon N Verstraete W 《Applied and environmental microbiology》2006,72(6):4323-4328
This study examined whether Legionella pneumophila is able to thrive on heat-killed microbial cells (necrotrophy) present in biofilms or heat-treated water systems. Quantification by means of plate counting, real-time PCR, and flow cytometry demonstrated necrotrophic growth of L. pneumophila in water after 96 h, when at least 100 dead cells are available to one L. pneumophila cell. Compared to the starting concentration of L. pneumophila, the maximum observed necrotrophic growth was 1.89 log units for real-time PCR and 1.49 log units for plate counting. The average growth was 1.57 +/- 0.32 log units (n = 5) for real-time PCR and 1.14 +/- 0.35 log units (n = 5) for plate counting. Viability staining and flow cytometry showed that the fraction of living cells in the L. pneumophila population rose from the initial 54% to 82% after 96 h. Growth was measured on heat-killed Pseudomonas putida, Escherichia coli, Acanthamoeba castellanii, Saccharomyces boulardii, and a biofilm sample. Gram-positive organisms did not result in significant growth of L. pneumophila, probably due to their robust cell wall structure. Although necrotrophy showed lower growth yields compared to replication within protozoan hosts, these findings indicate that it may be of major importance in the environmental persistence of L. pneumophila. Techniques aimed at the elimination of protozoa or biofilm from water systems will not necessarily result in a subsequent removal of L. pneumophila unless the formation of dead microbial cells is minimized. 相似文献
11.
Cytolytic activity of Legionella pneumophila 总被引:1,自引:0,他引:1
Iu F Bely? I S Tartakovski? S V Gul'nik G I Lavreneva V M Stepanov 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1989,(2):14-16
The properties of cytolysin and metalloproteinase purified by different methods have been studied. The physico-chemical properties of these proteins, including their molecular weight, immunodiffusion patterns, the degree of inhibition by EDTA and diethyl pyrocarbonate, amino acid composition, cytolytic and proteolytic activity, have proved to be similar. We have come to the conclusion that cytolysin and metalloproteinase have similar composition and metalloproteinase activity determines the cytolytic and necrotic activity of the above-mentioned cytolysin. 相似文献
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13.
Legionella pneumophila is a facultative intracellular pathogen responsible for severe lung disease in humans, known as legionellosis or Legionnaires' disease. Previously, we reported on the approximately 60-kDa glucosyltransferase (Lgt1) from Legionella pneumophila, which modified eukaryotic elongation factor 1A. In the present study, using L. pneumophila Philadelphia-1, Lens, Paris, and Corby genome databases, we identified several genes coding for proteins with considerable sequence homology to Lgt1. These new enzymes form three subfamilies, termed Lgt1 to -3, glucosylate mammalian elongation factor eEF1A at serine-53, inhibit its activity, and subsequently kill target eukaryotic cells. Expression studies on L. pneumophila grown in broth medium or in Acanthamoeba castellanii revealed that production of Lgt1 was maximal at stationary phase of broth culture or during the late phase of Legionella-host cell interaction, respectively. In contrast, synthesis of Lgt3 peaked during the lag phase of liquid culture and at early steps of bacterium-amoeba interaction. Thus, the data indicate that members of the L. pneumophila glucosyltransferase family are differentially regulated, affect protein synthesis of host cells, and represent potential virulence factors of Legionella. 相似文献
14.
Legionella pneumophila was detected and identified by an immunoblot assay using a monoclonal antibody specific to serogroups 1 to 8. Samples containing L. pneumophila were plated on buffered charcoal yeast extract agar supplemented with glycine, vancomycin, and polymyxin B. After incubation at 35 degrees C for 3 days, colonies were transferred to nitrocellulose membranes by blotting. Simultaneous detection and identification of L. pneumophila were done by treating the membrane with the monoclonal antibody and a peroxidase conjugate to mouse immunoglobulins. A diffuse cross-reaction was observed with Pseudomonas fluorescens colonies, but this was a low-level reaction that could easily be differentiated from the strong specific reactions to L. pneumophila. 相似文献
15.
A simple and reproducible method has been developed to transform Legionella pneumophila by electroporation. Effects of different conditions, including electric field strength, pulse length, DNA quality and cell density, were evaluated. Using our method, an efficiency of up to 6 x 10(7) transformants/microg DNA was obtained. This optimized transformation procedure should efficiently facilitate gene manipulations in L. pneumophila, such as plasmid transfer, transposon mutagenesis, library transformation for complementation cloning, etc. 相似文献
16.
Anders Sonesson Erik Jantzen Klaus Bryn Lennart Larsson Jan Eng 《Archives of microbiology》1989,153(1):72-78
Lipopolysaccharide isolated from Legionella pneumophila (Phil. 1) was examined for chemical composition. The polysaccharide split off by mild acid hydrolysis contained rhamnose, mannose, glucose, quinovosamine, glucosamine and 2-keto-3-deoxyoctonate, in molar proportions 1.6:1.8:1.0:1.5:4.1:2.7. Heptoses were absent and glucose was probably mainly phosphorylated. The carbohydrate backbone of the lipid A part consisted of glucosamine, quinovosamine and glycerol, in the molar ratios 3.9:1.0:3.4, with glycerol as a phosphorylated moiety. A complex fatty acid substitution pattern comprising eight O-ester-linked, exclusively nonhydroxylated acids, and nineteen amide-linked, exclusively 3-hydroxylated acids was revealed. Both straight- and branched (iso and anteiso) carbon chains occurred. The major hydroxy fatty acid was 3-hydroxy-12-methyltridecanoic acid and six others were of a chain-length above 20 carbon atoms, with 3-hydroxy-20-methyldocosanoic acid as the longest. Two dihydroxy fatty acids, 2,3-dihydroxy-12-methyltridecanoic and 2,3-dihydroxytetradecanoic acids, were also detected. These results suggest that L. pneumophila contains a rather complex and unusual lipopolysaccharide structure of considerable biological and chemotaxonomic interest.Abbreviations LPS
lipopolysaccharide
- PS
polysaccharide
- KDO
2-keto-3-deoxy-octonate
- GC
gas chromatography
- GC-MS
gas chromatograph-mass spectrometer combined instrument
- CI
chemical ionization
- EI
electron impact
- HF
hydrofluoric acid
- TFA
trifluoroacetyl
- TMS
trimethylsilyl 相似文献
17.
Rapid detection of Legionella pneumophila by flow cytometry 总被引:4,自引:0,他引:4
18.
Ferric reductase enzymes requiring a reductant for maximal activity were purified from the cytoplasmic and periplasmic fractions of avirulent and virulent Legionella pneumophila. The cytoplasmic and periplasmic enzymes are inhibited by zinc sulfate, constitutive and active under aerobic or anaerobic conditions. However, the periplasmic and cytoplasmic reductases are two distinct enzymes as shown by their molecular weights, specific activities, reductant specificities and other characteristics. The molecular weights of the cytoplasmic and periplasmic ferric reductases are approximately 38 and 25 kDa, respectively. The periplasmic reductase (Km = 7.0 m) has a greater specific activity and twice the affinity for ferric citrate as the cytoplasmic enzyme (Km = 15.3 m). Glutathione serves as the optimum reductant for the periplasmic reductase, but is inactive for the cytoplasmic enzyme. In contrast, NADPH is the optimum reductant for the cytoplasmic enzyme. Ferric reductases of avirulent cells show a 2-fold increase in their activities when NADPH is used as a reductant in comparison with NADH. In contrast, ferric reductases from virulent cells demonstrated an equivalent activity with NADH or NADPH as reductants. With the exception of their response to NADPH, the ferric reductase at each respective location appears to be similar for avirulent and virulent cells. 相似文献
19.
Characteristics of the cytolysin of Legionella pneumophila 总被引:2,自引:0,他引:2
Iu F Bely? Iu V Vertiev I S Tartakovski? Iu V Ezepchuk S V Prozorovski? 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1988,(2):4-7
A thermolabile cytolysin was purified from liquid culture of L. pneumophila. Its homogenicity was determined by the Ouchterlony double immunodiffusion and SDS-electrophoresis in polyacrylamide gel. The molecular weight of cytolysin was ca. 37 kDa. Analysis of amino acid composition revealed a high proportion of aromatic, dicarbonic amino acids, and methionine. The minimal cytolytic concentration for CHO cells and erythrocytes was ca. 1 microgram/ml: Purified cytolysin in doses of 10-60 micrograms caused haemorrhage and necrosis when injected i. c. into guinea pigs. 相似文献
20.
Temperature-regulated formation of mycelial mat-like biofilms by Legionella pneumophila 总被引:1,自引:0,他引:1
Piao Z Sze CC Barysheva O Iida K Yoshida S 《Applied and environmental microbiology》2006,72(2):1613-1622
Fifty strains representing 38 species of the genus Legionella were examined for biofilm formation on glass, polystyrene, and polypropylene surfaces in static cultures at 25 degrees C, 37 degrees C, and 42 degrees C. Strains of Legionella pneumophila, the most common causative agent of Legionnaires' disease, were found to have the highest ability to form biofilms among the test strains. The quantity, rate of formation, and adherence stability of L. pneumophila biofilms showed considerable dependence on both temperature and surface material. Glass and polystyrene surfaces gave between two- to sevenfold-higher yields of biofilms at 37 degrees C or 42 degrees C than at 25 degrees C; conversely, polypropylene surface had between 2 to 16 times higher yields at 25 degrees C than at 37 degrees C or 42 degrees C. On glass surfaces, the biofilms were formed faster but attached less stably at 37 degrees C or 42 degrees C than at 25 degrees C. Both scanning electron microscopy and confocal laser scanning microscopy revealed that biofilms formed at 37 degrees C or 42 degrees C were mycelial mat like and were composed of filamentous cells, while at 25 degrees C, cells were rod shaped. Planktonic cells outside of biofilms or in shaken liquid cultures were rod shaped. Notably, the filamentous cells were found to be multinucleate and lacking septa, but a recA null mutant of L. pneumophila was unaffected in its temperature-regulated filamentation within biofilms. Our data also showed that filamentous cells were able to rapidly give rise to a large number of short rods in a fresh liquid culture at 37 degrees C. The possibility of this biofilm to represent a novel strategy by L. pneumophila to compete for proliferation among the environmental microbiota is discussed. 相似文献