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This paper presents the influence of penicillin, erythromycin, Oxytetracycline and streptomycin on aquatic microorganisms isolated from three reservoirs with varied extent of environmental pollution (Sulejów Reservoir, Zegrze Reservoir and Vistula River). The experiments were conducted in especially prepared microcosms (aerated 15 l aquariums). From among the examined antibiotics streptomycin showed the longest activity in the water environment (27 days), followed by Oxytetracycline (22 days). Erythromycin had 13 days activity while the penicillin only 4 days. The highest number of bacteria was observed in the Vistula, fewer in Zegrze Reservoir. Sulejów Reservoir was characterized by the lowest number of bacteria. The strains isolated from Sulejów Reservoir were characterized by higher degree of biodiversity than those from Zegrze Reservoir or Vistula River. The dominant genera were Pseudomonas (49%), followed by Acinetohacter (21 %), Flavomonas (9%), Alcaligenes (9%), Vibrio, Moraxella and Oligella. The Vistula River was dominated by Aeromonas (88%) and Pseudomonas (12%) genera. The strains isolated from Sulejów Reservoir were more sensitive to antibiotics than those from the much more polluted Vistula, this being evidenced by lower MIC and MBC values.
The wild-type Bacillus subtilis spore protein, SspCwt, binds to DNA in vitro and in vivo and changes the conformation of DNA from B to A. Synthesis of the cloned SspCwt gene in Escherichia coli also causes large increases in mutation frequency. Binding of SspCwt to transforming DNA from Haemophilus influenzae made the DNA resistant to ultraviolet (UV) radiation. The mutant protein, SspCala, which does not bind DNA, did not change the UV resistance. The UV sensitivity of the DNA/SspCwt complex was not increased when the recipients of the DNA were defective in excision of pyrimidine dimers. These data indicate that the H. influenzae excision mechanism does not operate on the spore photoproduct formed by UV irradiation of the complex. Selection for the streptomycin- or erythromycin-resistance markers on the transforming DNA evidenced significant mutations at loci closely linked to these, but not at other loci. SspCwt apparently entered the cell attached to the transforming DNA, and caused mutations in adjacent loci. The amount of such mutations decreased when the transforming DNA was UV irradiated, because UV unlinks linked markers.
An increase in number of Salmonella serovar Mbandaka in animals was observed in Poland in the years 1995 - 1997. Eighty seven Salmonella serovar Mbandaka strains isolated from animal feed, poultry and food products were examined biochemically. Two biotypes were found, but 96.6% oTTfitf strains belonged to inositol-positive biotype I. All strains tested were lysed by phage O-l. Resistance to at least one antimicrobial agent was found in 28.7% of examined Salmonella serovar Mbandaka strains and 88% of them showed multi-resistance. Resistance to tetracycline and streptomycin was found to be the most common. Four out of 87 / strains showed resistance to nalidixic acid. One of them proved to be enrofloxacin-resistant. Most of the Salmonella serovar Mbandaka strains (95.4%) were plasmid free. The occurrence of 4 plasmid profiles was observed in 4 different strains. Two strains carried large single plasmids of about 38.7 MDa and 70.8 MDa. Two others harboured, respectively, 2 and 3 small plasmids of less than 2.0 MDa molecular weight.
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