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Aims: To examine effects of various environmental factors on adsorption and inactivation of Pseudomonas aeruginosa-specific phages: d (family Podoviridae), J-1, r-1 and 001A (family Siphoviridae) and their ability to inhibit bacterial growth and biofilm formation. Methods and Results: The phages examined in the study were clonally different, as revealed by RFLP. The temperature in the range 7-44°C had no influence on the adsorption of Podoviridae, but did affect Siphoviridae adsorption, particularly 001A. All phages were significantly stable at pH 5-9, and phages d and 001A even at pH 3. Most of the examined carbohydrates and exopolysaccharides of the original host efficiently inactivated phage d, while phages r-1 and J-1 were inactivated considerably only by the amino acid alanine. Silver nitrate efficiently inactivated all the phages, while Siphoviridae were more resistant to povidone-iodine. Serum of nonimmunized rats had no influence on phage inactivation and adsorption. Only phage d showed ability to effectively inhibit in vitro bacterial growth and biofilm formation. Conclusions: The examined environmental parameters can significantly influence the adsorption and viability of Ps. aeruginosa-specific phages. The phage d is a good candidate for biocontrol of Ps. aeruginosa.

The aim of the study was to screen various kinds of samples for Pseudomonas aeruginosa specific phages and to isolate and partially characterize those with broad activity spectra. The Pseudomonas specific phages were isolated using an enrichment procedure with single strains or the cocktail of P. aeruginosa strains as hosts. Using the described procedure, phages were successfully isolated only from water samples, while in soil and feces no Pseudomonas specific phages were detected. The lytic spectra of isolated phages were determined by spot method on lawns of 33 P. aeruginosa strains and five species belonging to family Enterobacteriaceae. The results showed that among isolated phages, 001A, delta, and I possessed the broad activity spectra, as were able to plaque on more than 50% of tested P. aeruginosa strains, while none of the phages were able to lyse the other tested species. Significant differences in phage activity spectra were not observed when P. aeruginosa cocktail was applied for sample enrichment. The most of the phages examined by electron microscopy belonged to family Siphoviridae, while the broad activity spectra isolates, except for 001A, possessed morphological characteristics of family Podoviridae. Digested DNA of the phages delta and I showed similar patterns, indicating the prevalence and success of this phage type in the environment.

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The possibility of using low-nutrient R2A medium for determining the total count of aerobic mesophilic bacteria was investigated. Sampling of water from particular points of water treatment and distribution at Kruševac drinking water treatment plant was conducted. The samples were inoculated simultaneously on Plate Count Agar (PCA) and R2A media, and incubated at 37 °C and at room temperature. The bacterial count was determined after 48, 72, 120 and 168 h. The statistical analysis of the results showed significantly higher bacterial count on R2A medium compared to PCA. Moreover, a significantly higher bacterial count developed at room temperature compared to the temperature of 37 °C. R2A medium recorded 3.6% of unsafe samples in the distribution system after the 7-day incubation at room temperature. On the basis of the obtained results, an optimum method for determining the total count of aerobic mesophilic bacteria for all investigated waters has been defined. The process of incubation is predictable and it can be described by a mathematical model in the form of a polynomial of the second or the third power.

A study has been done of the primary microbiolooical purification of mixed oil refinery and municipal wastewater using the active sludge process in a two-stage laboratory set-up. The advanced - secondary microbiological treatment of the mixed wastewaters was accomplished by using biologically active carbon. The highest total effect of the organic matter removal for both the primary and secondary microbiological treatment was achieved when the two wastewaters were mixed in the ratio 1:1, and it ranged from 97.7 to 99.2 %, The organic matter load in the effluent expressed as BOD5, was 0.3 - 5.7 mg O2/dm3. When conditions in the columns containing biologically active carbon were changed from aerobic into anaerobic ones, the denitrification bacteria were allowed to use the adsorbed organic matter as the substrate. In this way, the achieved nitrate removal was up to 72 %. It was found that active carbon had adsorbed the organic matter 1.37 - 2.10 times more than was its adsorption capacity, while the free surface degree was in the ranoe of 44.5 - 59.7 %. On the basis of the obtained results, the kinetic coefficients were calculated for both the primary and secondary microbiological treatment of the mixture of the oil refinery and municipal wastewaters. Finally, two alternatives of the technological procedure were proposed for such treatment.