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At least 1,153 records · Page 64Linked to original sources
PubMed2003

Evasion of cellular ocular defenses by contact lens isolates of Serratia marcescens.

PURPOSE: Contact lens contamination by Serratia marcescens can lead to the development of microbial keratitis and contact lens-induced acute red eye, particularly during overnight contact lens wear. The aim of this study was to investigate the interaction of S. marcescens with polymorphonuclear leukocytes (PMNs), which occur in closed-eye tears. METHODS: The respiratory burst of PMNs, when incubated with S. marcescens, was measured using chemiluminescence. Phagocytosis of planktonic and biofilm-grown bacteria by PMNs was also determined. RESULTS: Some strains of S. marcescens did not induce a respiratory burst from PMNs and resisted phagocytosis regardless of opsonization. Phagocytic resistance and growth in the presence of PMNs was markedly increased when bacteria were grown as a biofilm on a contact lens. CONCLUSIONS: The ability of S. marcescens to resist phagocytosis and grow to high levels in the presence of PMNs, particularly when grown as a biofilm on contact lenses, may be a mechanism by which this bacterium can survive the ocular host defense system, grow, and cause keratitis or other adverse responses.

Bacteriological Techniques↗
PubMed1992

Analysis of bacteriolytic activity patterns, a novel approach to the taxonomy of enterococci.

The bacteriolytic activities of different group D streptococcal species on various media and substrates were studied. Our results showed that all of the enterococcal species which we tested had bacteriolytic activity on at least one of the media used, while the group D nonenterococcal species had no such activity. In addition, using culture media containing different additives and different pH values, we defined seven major groups of bacteriolytic activity (lyogroups), each of which overlapped with one species (four lyogroups), two species (two lyogroups), or four species (one lyogroup). The detection of enterococcal lyogroups proved to be as reliable for species identification as the conventional methods presently in use.

Bacteriolysis↗
PubMed1992

Marinobacter hydrocarbonoclasticus gen. nov., sp. nov., a new, extremely halotolerant, hydrocarbon-degrading marine bacterium.

On the basis of phenotypical characteristics and analysis of 16S rRNA sequence, a new species belonging to a new genus is described, and the name Marinobacter hydrocarbonoclasticus is proposed. This organism, isolated from Mediterranean seawater near a petroleum refinery, is a gram-negative, aerobic, rod-shaped bacterium. It grows at NaCl concentrations of 0.08 to 3.5 M and uses various hydrocarbons as the sole source of carbon and energy. Its DNA has a guanine-plus-cytosine content of 52.7 mol%. The 16S rRNA analysis shows a clear affiliation between M. hydrocarbonoclasticus and the gamma group of the phylum Proteobacteria. A close phylogenetic relationship appears among the species Marinomonas vaga, Oceanospirillum linum, Halomonas elongata, and Pseudomonas aeruginosa. Because of the impossibility of finding a single most closely related species, we suggest that this bacterium be assigned to a new genus, at least temporarily. The possibility of a revision of this status when new data appear is, however, not excluded. The type strain is M. hydrocarbonoclasticus SP.17 (= ATCC 49840).

Bacteriolysis↗
PubMed1993

A new approach to use of bacteriolytic enzymes as a tool for species identification: selection of species-specific indicator strains with bacteriolytic activity towards Enterococcus strains.

We describe the bacteriolytic activity of 377 group D Enterococcus isolates expressed towards 25 Enterococcus strains belonging to different species and Micrococcus luteus ATCC 4698. Of the 26 indicator strains used to reveal bacteriolytic activity, 5 were lysed by all of the strains of some species and were not lysed by all of the strains of other species. The use of these indicator strains allowed us to devise a new method to differentiate group D Enterococcus strains, based on qualitative analysis (lysis or no lysis of the indicator strains) of bacteriolytic activity. The bacteriolytic patterns obtained fell into six bacteriolytic groups corresponding (98% agreement) to species or groups of enterococci as determined by a comparison with data from a phenetic similarity study.

Bacterial Typing Techniques↗
PubMed1975

Characteristics of a Bacillus megaterium bacteriophage.

A bacteriophage which infects and lyses Bacillus megaterium ATCC 19213 was isolated from the soil. The phage produces lysis on nine strains of B, megaterium tested but did not lyse a Bacillus cereus or Bacillus licheniformis strain, nor any of eight Bacillus subtilis strains tested. Physical characteristics of the phage including morphology, size, thermal and pH stability, and buoyant density were examined. The nucleic acid is double-stranded DNA of mol. wt. 41.7 times 10 and 36 to 38.5 mol percent guanine plus cytosine (G+C).

Bacillus cereus↗
PubMed1975

Characterization of different plaque-forming and defective temperate phages in Agrobacterium.

Four Agrobacterium tumefaciens temperate phages (PB2A, PB6(omega), PV-1(LV-1) and PS8), were shown to have the same genome size. Moreover hybridization experiments by the heteroduplex method and electron microscopy showed a 100% homology between these four phage genomes. Indications for lysogeny were found by direct means for the Agrobacterum timefaciens strain 396, Agrobacterium radiobacter strain 8149 and Agrobacterium species 0362 and by the electron microscope negative staining technique for the A.tumefaciens strains b6-806,b6-6,b6s3,b2as,cv-1,4452,11156,11158,396, and 925; for A.radiobacter strains tr-1 and 8149, the latter being bi-lysogenic, and for the A. species 0362. These isolated phage particles, most of which appear to be defective, could be grouped into different classes. No particles could be detected in the lysates of A. tumefaciens RV3, A. radiobacter strains 4718 and S1005, and A. species 0363. Further characterization by genome size was carried out for the defective temperate phages PB6-806, P4452,P8149 and P0362. No evidence for homology between PB6-806 and PB6 omega could be found. The defective phages PB6-806 and P4452 showed the same morphology but a different genome size, whereas the two phages P0362 and P8149 had a very different morphology and genome size.

Bacteriolysis↗
PubMed1976

The effect of host-cell starvation on virus-induced lysis by MS2 bacteriophage.

Infection of glucose, sulphur or nitrogen starved cells with MS2 virus results in the production of progeny virus but the absence of cell lysis and the failure of progeny virus release. Addition of glucose of sulphur to the correspondingly starved cells results in the normal release of virus within 40 to 60 min. Return of nitrogen to nitrogen-starved cells, however, does not result in the release of virus, even after 1 1/2 h. In experiments with uninfected, starved cells it was found that glucose or sulphur starved cells begin dividing within 45 min after the limiting compound is returned. In contrast, nitrogen-starved cultures have not begun to divide 1 1/2 after the return of nitrogen. The correlation between the time it takes for starved, infected cultures to resume lysis after the return of the limiting compound and the time similarly starved, but infected, cells normally begin division after addition of the limiting compound supports the hypothesis that lysis by RNA phage is related to cell division and may result at the time of cell division from failure of the cells to divide properly.

Bacterial Proteins↗
PubMed1981

Properties of the virulent form of a mitomycin C- or temperature-induced thermophilic bacteriophage.

A virulent bacteriophage was isolated from lysates of Bacillus stearothermophilus strain NU-10 induced either by treatment with mitomycin C or by shifts in temperature. Optimum conditions for induction, morphology and other properties of the virus are described. Chloroform treatment and shifts in temperature of producer cells released approximately similar amounts of phage as did mitomycin induction, suggesting an effect on release rather than on synthesis of the virus.

Bacteriolysis↗
PubMed1981

Inhibition of T7 development at high concentrations of the phage.

Escherichia coli B exposed to high doses of bacteriophage T7 did not lyse. A similar effect was observed when the high dose was added within the first 7 min after primary infection. No viable phage was formed. DNA synthesis was inhibited rapidly and the nucleoid structure was absent. Protein synthesis was in general markedly reduced and so were the activities of the phage-specific enzymes endolysin and DNA polymerase. However, phage genes were transcribed both by the host RNA polymerase and by the phage-specific enzyme. We suggest that inhibition of phage development is due to structural alterations occurring in the cell wall/membrane such that replication is inhibited.

Bacteriolysis↗
PubMed1981

Effect of defective phages on the cell membrane of Bacillus subtilis and partial characterization of the phage protein involved in killing.

In order to investigate whether defective phages of Bacillus subtilis killed sensitive bacteria by a lysis from without mechanism, the minimal number of phages required for killing was determined. This figure was found to vary with the m.o.i., giving a value of 1 on extrapolation to an m.o.i. of 0. This excluded lysis from without as the only killing mechanism, although it might play a role at high m.o.i.s. This was confirmed by experiments on leakage of ATP and u.v.-absorbing material, the uptake of oxygen and the effect of the phages on the membrane potential. Apart from a short, initial leakage of ATP, the cell membrane was not affected at low m.o.i.s. These results lead to the conclusion that at low m.o.i.s. the phages acted on a cytoplasmic component. Treatment of defective phages for 10 min at pH 2.5 resulted in breakdown of the phages without complete abolition of the killing activity. The active component, which was shown not to be DNA, could not be isolated from the mixture, but SDS gel electrophoresis of PBS X and a non-killing mutant of this phage suggested that a protein with a mol. wt. of 85000 was involved in killing.

Bacillus subtilis↗
PubMed1981

phi 6-resistant phage-producing mutants of Pseudomonas phaseolicola.

phi 6R mutants of Pseudomonas phaseolicola HB10Y were isolated and 12 out of 129 spontaneous mutants were found to produce phages during cellular growth. Following mitomycin C treatment 39 out of 82 isolated resistant mutants were phage-producing ones. The decrease in growth rate of these mutants corresponded roughly to the number of phages liberated into the medium. Prolonged storage of the mutants resulted in loss of production which could be regained by growing them with a high multiplicity of phages. The phage production phenomenon was independent of phage adsorption since both adsorbing and non-adsorbing phage-producing mutants were found. Occasionally, the phage-producing strains showed abnormally high numbers of intracellular phage particles in sectional material. The producers were found to be 2 to 5 times more resistant than the normal host or non-producing phi 6R strains to the lytic enzyme associated with the phi 6 virion, indicating that they had an altered cell wall structure. The lytic enzyme of phi 6, needed both in penetration and progeny release, was less active on the altered cell wall, leading to diminished infection efficiency and deficient plaque formation.

Adsorption↗