Acta microbiologica Polonica最新文献

The production of extracellular and intracellular secondary metabolites by 13 Aspergillus species has been directly detected using the agar plug technique. In addition to several unknown compound A. aculeatus, A. ochraceus and A. terreus were found to be the highest producers of extracellular secondary metabolites, while the lowest producer species were A. tamarii, A. rugulosus in addition to A. oryzae whose secondary metabolites couldn't be detected by this technique. In case of intracellular secondary metabolites, the highest producer species were A. flavus, A. nidulans and A. wentii, while the lowest producers were A. clavatus, A. tamarii and A. violaceous. All the examined species could be distinguished on the basis of their secondary metabolite profiles indicating the potential role of secondary metabolites in the chemotaxonomy of Aspergilli.

Exo-1,4-beta-glucanase (E.C. 3.2.1.91) was successively purified by precipitation with acetone, followed by gel filtration on Sephadex G-100 and chromatographed onto DEAE-cellulose. A typical procedure provided 47.14 fold purification with 72.8% yield. The molecular mass of the purified enzyme was found to be 88 kDa by SDS-PAGE. The pH optimum of the enzyme was 5.2 and maximum activity was obtained at 45 degrees C. Km value against alpha-cellulose was 0.65 mg mL(-1). Alpha-cellulose and filter paper were the best substrates for enzyme activity. Enzyme was activated by Mn2+ and Fe3+, inactivated by Cu2+ and completely inhibited by Hg2+ and Ag+.

We have used plasmid pLTV3, which carries transposon Tn917, to obtain a series of mutants of Listeria monocytogenes EGD showing varied degrees of resistance to ampicillin and other beta-lactam antibiotics, including imipenem. In this paper we focus on the characteristics of two strains in which decreased susceptibility to ampicillin is accompanied by changes in the structure of the cell wall murein and cell-wall related changes of phenotype.

The continuous growth of world population and its concentration in the urban areas require food supplies that are continuous, sufficient and of good quality. To resolve this problem techniques have been developed for increasing food quantity and quality. The techniques are applied throughout the food chain from production, conservation and during distribution to the consumers (from "the field to the fork"). During handling of food, chemicals are often deliberately added to achieve improved processing and better quality. This is one of the main reasons food undergoes different kinds of contamination. This overview focuses on the application of supercritical fluids as media for handling food materials during processing with the perspective of reducing chemical contamination of food. Examples of developmental applications of this technique and on research work in process are presented. Emphasis is given to extraction and biotransformation techniques.

Seasonal variations in the hydrocarbon-degrading potential of soil samples from an unimpacted site in the Kuwaiti Burgan oil field environment were studied under mesophilic conditions. Hydrocarbon-degrading microorganisms occurred but varied all-year-round, and their numbers ranged from 1.3 x 10(7) to 9.3 x 10(7) CFU g(-1) dry soil, while hydrocarbon-degrading fungi ranged from 3.0 x 10(4) - 3.8 x 10(5) CFU g(-1) dry soil, depending on the sampling period. These hydrocarbon-degraders also comprised variable but generally high proportions of the total aerobic heterotrophic organisms (2 to > 98%) for bacteria and lower levels (7-9%) for fungi. The crude oil-degrading capacity of the oil-degrading populations (bacteria and fungi) ranged from 80-95% of the hexane-extractable fractions. Differential inhibition studies carried out on soil samples showed that bacteria were the greater contributors to hydrocarbon degradation (79-92%) than fungi. Pure hydrocarbon substrates, hexadecane and phenanthrene, were degraded to near completion after a 28-day incubation by both the bacterial and fungal portions of the soil flora.

The purpose of the present study was to determine whether there is the relation between the virulence of used HSV-1 strains and inhibition of apoptosis. HEp-2 cells were induced to apoptosis by osmotic shock after infection by HSV-1 strains. HSV-1 ts, earlier described as less virulent for mice inhibited apoptosis in smaller degree than native strain and HSV-1 tr. We suggest that this is due to the hyperproduction of IFN alpha by human cells after the stimulation by this strain. All strains of HSV-1 didn't inhibit apoptosis in the presence of IFN alpha and apoptosis was inhibited by anti IFN alpha antibodies. We confirm that IFN alpha plays an important function in controlling acute HSV-1 infection.

The aim of this study was to compare the influence of antimicrobials (clindamycin, metronidazole and polymyxin B) on the expression of adhesion molecules (VCAM-1, ICAM-1 and E-selectin) on the HMEC-1 cell line stimulated by LPS and enterotoxin of B. fragilis. LPS was extracted from two reference: ATCC 43858 and NCTC 11295 and one isolated in our laboratory (W2) enterotoxigenic strains, and one nonenterotoxigenic reference strain--IPL E 323. Enterotoxin preparations (Tox 1 and Tox 2) were isolated from supematant of B. fragilis ATCC 43858 culture and purified. HMEC-1 cell line was stimulated with bacterial preparations at concentration of 10 mg/ml. For measuring the expression of adhesion molecules we used ELISA test. Clindamycin, metronidazole and polymyxin B supressed the ICAM-1 expression when endothelium was stimulated with B. fragilis LPS and augmented ICAM-1 expression by Tox 1 and Tox 2. The expression of VCAM-1 was augmented by antimicrobials when endothelium was stimulated with LPS or enterotoxin preparations. The expression of E-selectin was differentiated.

We analyzed polymorphism of the PCR-amplified 16S-23S rDNA spacer of Aeromonas species. A total of 69 isolates representing 18 DNA hybridization groups were used in this study. The analysis of PCR products of 16S-23S rDNA spacers revealed patterns consisting of two to eight DNA fragments. The fragment sizes ranged from 730 to 1050 bp. DNA patterns revealed a considerable genetic diversity between species and within a species. When a procedure to eliminate heteroduplex formation was performed, the number of bands was reduced to 2-5. Nevertheless the homoduplex ISR (intergenic spacer region) patterns obtained were not useful for species distinguishing.

Studies have been conducted on L-phenylalanine (L-Phe) production and phenylalanine ammonia lyase (PAL) stabilization in the presence of several optimum effectors and reducing agents under bioconversion of transcinnamic acid (t-CA) conditions during repeated batch operations. L-Phe production was maximized and reuseability of PAL catalyst was extended to eight consecutive cycles (repeated batches) in the presence of optimum effectors (glutamic acid, polyethylene glycol and glycerol), thioglycolic acid and sparging with nitrogen gas. These best optimum bioconversion conditions desensitize the PAL catalyst to substantially elevated higher substrate t-CA concentrations and inhibit inactivation of PAL enzyme over longer reaction periods compared to the control. The fed batch mode operation of bioconversion of total t-CA (300 mM) to L-Phe was superior (65.2%, conversion), comparing with conventional batch and repeated batch (58.4%, conversion) operations after 120 h. Gamma irradiation process was employed to polymerize and crosslink polyvinyl alcohol (PVA) with N,N'-methylene-bisacrylamide (BIS) agent. The use of immobilized PAL biocatalyst containing cells in PVA-BIS copolymer gel carrier produced by radiation polymerization is obviously advantageous with regards to the yield of L-Phe which was increased in average 1.2-fold when compare to those obtained with free cells during optimum bioconversion process. When comparing the magnitudes of gamma irradiation effects on immobilized entrapped yeast cells in PVA-BIS copolymer gel carrier using scanning electron microscopy it was show that yeast cells were protected and capable to overcome these conditions and had normal shape and other features as free (unirradiated) intact yeast cells. Optimum conditions for continuous production of L-Phe by PVA-BIS copolymer carrier entrapped yeast cells in a packed bed column reactor in recycle fed-batch mode were investigated. Under these optimum conditions L-Phe accumulated to concentration 240.1 mM represts a total conversion yield of 80% (w/w) from (300 mM) t-CA after 84 h of reaction process, which was higher than that obtained after 120 h of reaction, 65.2% (w/w) from (300 mM) t-CA with free cells in fed-batch mode. The results also demonstrated that during about 4 weeks of repeated continuous recycle fed batch mode experiments (using immobilized cells in packed bed reactor), the final production of L-Phe concentrations decreased gradually in eight consecutive runs with no sign of breakage or disintegration of the carrier gel beads.

Soils of pine forests in the Bytnica Forestry District, Poland, are poor in nutrients readily accessible to plants. The excessively acidic reaction of the soils, typical for soils under pine forests, unfavourably affects the growth of microorganisms whose numbers are lower than in soils under deciduous and mixed forests. In the pine forests of the studied forestry there were outbreaks of a defoliating insect - pine beauty moth (Panolis flammea L.), which resulted in over 60% defoliation of the trees. The studies were carried out on the area of tree stands subjected to gradation by leaf-eating insects (sprayed and not sprayed) and healthy stand of the same age class (age 60 to 70 years). The studies revealed increased number of soil microorganisms in samples taken from the area affected by pine beauty moth gradation in the case of both unsprayed areas and those sprayed with the pesticide. The occurrence in these soils of larger numbers of ammonifying and denitrifying bacteria points to the presence of conditions favouring the growth of heterotrophic organisms. Changes in the number of actinomycetes and fungi in soils under tree stands subjected to gradation by insects, compared to healthy stands, can be a consequence of a change of environmental conditions (e.g. % content of organic carbon). Soils under defoliated tree stands show higher biochemical activity related to nitrogen cycling in the pine forest ecosystem. This leads to higher availability of organic nitrogen for conversion to inorganic forms of nitrogen, which are utilised by trees. Further changes occurring in soils under forest stands affected by gradation by leaf-eating insects would allow to gain knowledge on the ecological consequences of the use of insecticides in the protection of pine stands against harmful insects, with particular stress on those situations in which pine stands not threatened by complete defoliation are sprayed.