Biomedical subjects

U Szewzyk

Publications and source records attributed to U Szewzyk.

24 records · Page 2Linked to original sources

PubMed1997

Isolation of new bacterial species from drinking water biofilms and proof of their in situ dominance with highly specific 16S rRNA probes.

A polyphasic approach involving cultivation, direct viable counts, rRNA-based phylogenetic classification, and in situ probing was applied for the characterization of the dominant microbial population in a municipal drinking water distribution system. A total of 234 bacterial strains cultivated on R2A medium were screened for bacteria affiliated with the in situ dominating beta subclass of Proteobacteria. The isolates were grouped according to common features of their cell and colony morphologies, and eight representative strains were used for 16S rRNA sequencing and the development of a suite of strain-specific oligonucleotide probes. Phylogenetic analysis indicated that all of the isolates were hitherto unknown bacteria. Three of them, strains B4, B6, and B8, formed a separate cluster of closely related organisms within the beta 1 subclass of Proteobacteria. In situ probing revealed that (i) 67 to 72% of total bacteria, corresponding to more than 80% of beta-subclass bacteria, could be encompassed with the strain-specific probes and (ii) the dominating bacterial species were culturable on R2A medium. Additionally, two-thirds of the autochthonous drinking water population could be shown to be in a viable but nonculturable (VBNC) state by using a direct viable count approach. The comparison of isolation frequencies with the in situ abundances of the eight investigated strains revealed differences in their culturability, indicating variable ratios of culturable to VBNC cells among the strains. The further characterization of biofilms throughout the distribution network demonstrated strains B6 and B8 to be dominant bacterial strains in groundwater and distribution system biofilms. The other strains could be found at various frequencies in the different parts of the distribution system; several strains appeared exclusively in drinking water biofilms obtained from a house installation system.

Bacteria↗

PubMed1995

In situ identification of Legionellaceae using 16S rRNA-targeted oligonucleotide probes and confocal laser scanning microscopy.

Bacteria of the family Legionellaceae form a monophyletic group within the gamma-subclass of Proteobacteria. Based on comparative sequence analysis we constructed two oligonucleotide probes complementary to regions of 16S rRNA characteristic for Legionellaceae. Probe specificities were tested by whole-cell or dot-blot hybridization against 14 serogroups of Legionella pneumophila, 22 different Legionella spp. and 72 non-legionellae reference strains. Using optimized conditions both probes hybridized to all tested strains of L. pneumophila. Probes LEG226 and LEG705 hybridized to 71% and 90% of the Legionella species tested, respectively. With the exception of Methylomonas alba none of the non-target strains showed complete sequence homology within the target molecule. In a preliminary evaluation the results of classical techniques employing selective media, immunofluorescence and the probe assay were in good accordance for routine environmental and clinical isolates. L. pneumophila suspended in drinking water at approximately 10(3)-10(4) c.f.u. ml-1 could be rapidly detected by a combination of membrane filtration on polycarbonate filters and whole-cell hybridization. Even after incubation for 1 year a proportion of the released cells was still detectable. In situ hybridization also facilitated visualization of Legionella spp, cells in model biofilms. A combination of in situ hybridization and confocal laser scanning microscopy (CLSM) was used to analyse the three-dimensional arrangement of L. pneumophila within cells of the ciliated protozoan Tetrahymena pyriformis. Whole-cell probing with 16S rRNA-targeted oligonucleotides could, in the future, complement established techniques like immunofluorescence and PCR in ecological and epidemiological studies of Legionellaceae.

Animals↗

PubMed1994

Thermophilic, anaerobic bacteria isolated from a deep borehole in granite in Sweden.

A borehole drilled to a total depth of 6779 m in granitic rock in Gravberg, Sweden, was sampled and examined for the presence of anaerobic, thermophilic, fermenting bacteria and sulfate-reducing bacteria. Growth in enrichment cultures was obtained only from water samples collected from a specific sampling depth in the borehole (3500 m). The hole was cased down to a depth of 5278 m and open to the formation below that level. All the water below 2000 m in depth standing in the borehole at the time of sampling must have entered at the 5278-m level or below, during a prior pumping operation. A strong salinity stratification certifies that no major amount of vertical mixing had taken place. The depth from which bacteria could be enriched was that of a pronounced local minimum of salinity. Pure cultures of thermophilic, anaerobic, fermenting bacteria were obtained with the following substrates: glucose, starch, xylan, ethanol, and lactate. The morphology and physiology of the glucose- and starch-degrading strains indicate a relationship to Thermoanaerobacter and Thermoanaerobium species. All but one of the newly isolated strains differ however from those by lacking acetate as a fermentation product. The glucose-degrading strain Gluc1 is phylogenetically related to Clostridium thermohydrosulfuricum, with an evolutionary distance based upon rRNA sequence comparisons of 3%. No sulfate-reducing or methanogenic bacteria were found.

Journal Article↗

PubMed1993

In situ identification of bacteria in drinking water and adjoining biofilms by hybridization with 16S and 23S rRNA-directed fluorescent oligonucleotide probes.

Free-water-phase and surface-associated microorganisms from drinking water were detected and roughly identified by hybridization with fluorescence-labeled oligonucleotide probes complementary to regions of 16S and 23S rRNA characteristic for the domains Bacteria, Archaea, and Eucarya and the beta and gamma subclasses of Proteobacteria. Samples of glass-attached biofilms and plankton were taken from a Robbins device installed in a water distribution system. More than 70% of the surface-associated cells and less than 40% of the planktonic cells visualized by 4',6-diamidino-2-phenylindole staining bound detectable amounts of rRNA-targeted probes. These findings are an indication for higher average rRNA content and consequently higher physiological activity of the attached microbial cells compared with the free-living cells. All detectable cells hybridized with the bacterial probe, whereas no Archaea and no Eucarya cells could be detected. Simultaneous hybridization with probes specific for the beta and gamma subclasses of Proteobacteria revealed that microcolonies already consisted of mixed populations in early stages with fewer than 50 cells. These observations provide further evidence that the coexistence and interaction of bacteria in drinking water biofilms may be an integral part of their growth and survival strategies.

Bacteria↗

PubMed1993

Growth and survival of Serratia marcescens under aerobic and anaerobic conditions in the presence of materials from blood bags.

Several patients receiving blood transfusions during the summer of 1991 developed bacteremia after the transfusion. In all cases, the infection was caused by Serratia marcescens. The same strain of Serratia marcescens was isolated from the patients and from the outer surface of unfilled blood bags. The transport containers for the blood bags were made anoxic by using a catalyst in order to prevent microbial growth. The survival and growth of S. marcescens K202, which was isolated from the blood bags, was studied at different oxygen concentrations in deionized water containing materials derived from the blood bags. The rate of survival and growth of S. marcescens was highest under anaerobic conditions, in which growth occurred with all materials and even in deionized water alone. In contrast, S. marcescens did not survive in control cultures under semi-anaerobic and aerobic conditions. Growth was observed, however, under both aerobic and semi-anaerobic conditions in the presence of each of the tested blood bag materials. These findings indicate that the conditions in the transport containers for the blood bags were favorable for the survival and growth of S. marcescens.

Aerobiosis↗

PubMed1990

Starvation-specific formation of a peripheral exopolysaccharide by a marine Pseudomonas sp., strain S9.

The marine bacterium Pseudomonas sp. strain S9 produces exopolysaccharides (EPS) during both growth and total energy source and nutrient starvation. Transmission electron microscopy of immunogold-labeled cells demonstrated that the EPS is closely associated with the cell surface during growth (integral EPS), while both the integral form and a loosely associated extracellular (peripheral) form were observed during starvation. Formation and release of the latter rendered the starvation medium viscous. In addition, after 3 h of starvation in static conditions, less than 5% of the cells were motile, compared with 100% at the onset of starvation and approximately 80% subsequent to release of the peripheral EPS at 27 h of starvation. Inhibition of protein synthesis with chloramphenicol added before 3 h of starvation caused no increase in viscosity. However, addition of chloramphenicol at 3 h did not prevent the subsequent increase in viscosity displayed by S9 cells. The amount of integral EPS increased for both nontreated and chloramphenicol-treated S9 cells during the first hour of starvation, with a subsequent equal decrease. The chloramphenicol-treated cells, as well as cells of a transposon-generated mutant strain deficient in peripheral EPS formation, remained adhesive to a hydrophobic inanimate surface during the initial 5 h of starvation, whereas nontreated wild-type cells had progressively decreased adhesion capacity. During the initial 5 h of starvation, most of the nontreated cells but only a small fraction of the chloramphenicol-treated and mutant cells detached from the hydrophobic substratum.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Proteins↗