Acta microbiologica Polonica最新文献

Surface hydrophobicity is a widely distributed characteristic among human bacterial pathogens playing an important role in microbes retention by the incurrent siphon of a marine bivalve. Feeding retention experiments with the bivalve Mesodesma donacium was done with hydrophobic strains alone (Staphylococcus aureus, Salmonella paratyphi, Vibrio cholerae) or with mixed cultures using a hydrophilic strain (Aeromonas hydrophila). Results showed that hydrophobic bacteria are retained in greater numbers than hydrophilic bacteria. This difference is statistically significant. Hydrophobic strains also survive longer than hydrophilic ones in sea water. Surface hydrophobicity is to be considered as a factor influencing concentration of hydrophobic pathogens by filter feeding molluscs.

The conditions for batch and continuous production of ethanol, using immobilized growing yeast cells of Kluyveromyces lactis, have been optimized. Yeast cells have been immobilized in hydrogel copolymer carriers composed of polyvinyl alcohol (PVA) with various hydrophilic monomers, using radiation copolymerization technique. Yeast cells were immobilized through adhesion and multiplication of yeast cells themselves. The ethanol production of immobilized growing yeast cells with these hydrogel carriers was related to the monomer composition of the copolymers and the optimum monomer composition was hydroxyethyl methacrylate (HEMA). In this case by using batch fermentation, the superior ethanol production was 32.9 g L(-1) which was about 4 times higher than that of cells in free system. The relation between the activity of immobilized yeast cells and the water content of the copolymer carriers was also discussed. Immobilized growing yeast cells in PVA: HEMA (7%: 10%, w/w) hydrogel copolymer carrier, were used in a packed-bed column reactor for the continuous production of ethanol from lactose at different levels of concentrations (50, 100 and 150) g L(-1). For all lactose feed concentrations, an increase in dilution rates from 0.1 h(-1) to 0.3 h(-1) lowered ethanol concentration in fermented broth, but the volumetric ethanol productivity and volumetric lactose uptake rate were improved. The fermentation efficiency was lowered with the increase in dilution rate and also at higher lactose concentration in feed medium and a maximum of 70.2% was obtained at the lowest lactose concentration 50 g L(-1).

The putative product of orf13 from the genome of Haemophilus influenzae HP1 bacteriophage shows homology only to bacteriophage T1 Dam methyltransferase, and a weak similarity to the conserved amino acids sequence motifs characteristic of m6A-methyltransferases. Especially interesting is lack of characteristic motif I responsible for binding of S-adenosylmethionine. Despite this fact, a DNA sequence of HP1 bacteriophage of Haemophilus influenzae encoding methyltransferase activity was cloned and expressed in Escherichia coli using pMPMT4 omega expression vector. The cloned methyltransferase recognizes the sequence 5'-GATC-3' and methylates an adenine residue. The enzyme methylates both double- and single-stranded DNA substrates.

Random Amplified Polymorphic DNA (RAPD) method became widely applied for sensitive, efficient and fast distinguishing of different isolates of a given species, if pure culture is available. Problems with reproducibility and discriminatory power, frequently cited in the literature, can be overcome by precise optimization procedure allowing to achieve reliable conditions for each species analysed. Basing on two examples of different species, H. pylori and E. faecium, particular parameters of RAPD fingerprinting were evaluated with respect to selection of best working primers generating medium-complex profiles, using only high quality DNA samples and evaluation optimum for every reaction reagent. Stable and informative amplification patterns were obtained with different best working primers which could discriminate between all H. pylori and E. faecium strains tested. For both analysed species different optima were found, suggesting species-specific need of precise RAPD conditions evaluation. This study proved high sensitivity and efficiency of optimized RAPD profiling applicable for searching the epidemiology traces for both species.

The effects of cyanogenic Pseudomonas fluorescens strains introduced into soil on the kinetic of colony formation and bacterial community structure were investigated. About 7.8 x 10(8) and 1.2 x 10(9) cfu per g dry soil of TA1 and B2 were added to the soil portions, respectively. The parameters of colony formation by heterotrophic soil bacteria were determined. The bacterial community structure and phenotypic diversity were studied using concept of r/K strategies and echophysiological index, respectively. The physiological state of indigenous heterotrophic bacteria and gram-negative group did not change under the influence of the cyanogenic strains introduced. Phenotypic diversity of the soil bacteria also did not change significantly. However, some short-term shifts in community structure of indigenous heterotrophic bacteria were noticed. This study shows that the introduction of great numbers of cyanogenic P. fluorescens strains could be safely used as potential agents in biological control of soil-born pathogens.

The Ames test was applied to evaluation of the mutagenicity of month's samples of airborne particles from the center of Wrocław (SW Poland) collected in August and December 1997. The strains used for the study were TA 98, TA 100 and their derivatives: TA 98 NR, YG 1021, YG 1024, YG 1026, YG 1029, YG 1041, YG 1042. Both studied samples were mutagenic for almost all tested strains, with the exception of the August sample which did not influence the strain TA 100 without the metabolic activation with the S9 fraction. The December sample exhibited higher genotoxic activity than the August sample. Mutagenicity ratios of the strains with reduced nitroreductase and O-acetyltransferase activities were higher, and of the strain without the nitroreductase--lower than those of the parent strains. This indicates that nitro and amino derivatives of PAHs are responsible for the significant proportion of total mutagenicity of the studied samples of particulates. Metabolic activation with the S9 fraction caused the increase of the mutagenic activity of the samples, which indicates the presence of promutagens. The GC-MS analysis revealed the presence of known indirect mutagens from the PAHs group.

Antigenic properties of enterotoxigenic Bacteroides fragilis (ETBF) strains isolated in Poland were compared with reference strains. The agglutination and passive hemagglutination, SDS-PAGE analysis and immunoblotting tests as well as analyses of sugars and fatty acids were performed with lipopolysaccharide (LPS) preparations obtained from water-phase of phenol-water extracts. Some differences in serological reactivity between ETBF antigens were observed. The antigen of the NTBF (nonenterotoxigenic) reference strain IPL E-323 expressed weak cross-reactivity with sera against whole cells of ETBF strains in serological tests. There were some differences observed between ETBF and NTBF strains in fatty acids and sugar composition. The LPS preparations probably possess a common core structure and the O-specific polysaccharides of variable chain length.

The effects of hyperosmotic stress on expression of plasmid coded Yop and Yad A proteins--virulence factors of Y.enterocolitica serotype 0:9 were characterized. When cells were shifted to high osmolarity and cultured at 37 degrees C in medium without Ca2+ the production of Yops was inhibited. In contrast, the amount of Yad A protein was unaffected. Addition of glycine betaine to this culture alleviated the effect of high osmolarity. It was also found that hyperosmotic stress causes increased negative supercoiling of DNA in Y. enterocolitica 0:9. Changes in DNA supercoiling coincided with expression of Yop proteins. These results suggest that in high osmolarity the expression of yop genes may be regulated by DNA supercoiling.

Physiological conditions that could provide maximal rates of autolysis of Listeria monocytogenes were examined. L. monocytogenes was found to be refractory to most treatments that promote rapid autolysis in other bacteria. Best rates of autolysis were obtained after resuspending the cells in Tris-hydrochloride buffer at 37 degrees C with the pH optimum at 8.0. Autolysis was also efficiently promoted by the surfactant Triton X-100. Antibiotics that interfere with the biosynthesis of the cell wall murein (peptidoglycan) caused death of the cells without autolysis after prolonged incubation in the presence of the drug. Only nisin, which has been shown to bind in vitro to the murein precursors lipid I and lipid II brings about autolysis of L. monocytogenes cells, although with slower kinetics than in the case of Tris-HCl and Triton.