Resistance of the strains to each antibiotic taken separately, 

 frequency of mono-, di-, and polyresistant strains, as well as 

 resistance spectra (R-spectra) were recorded. 



To determine the resistance of heavy metals, the following 

 salts were used: Hg(NO,), 2H,0, Pb(NO,),. CdCl,. CuSO, 

 (waterless), and NiSOj in the range of 0.5 to 1,024 ng/ml. In 

 terms of the number of ions, this amounted to 0.4-882 for 

 Hg2=*; 0.35-670 for Pb-^ 0.3-627 for Cd-*; 0.2-464 for Co-^ 

 and 0.15-331 forCu^ 



Choice of the concentrations of antibiotics and heavy 

 metals and assessment of the bioresistance level of marine 

 microorganisms were based on literature data. Kulskyi er al. 

 (1986), working on the problems of natural sensitivity of 

 different representatives of microflora from aquatic and soil 

 biocenoses, published information on maximum permissible 

 concentrations (MFC) of these pollutants. 



The genotoxic effects of cultured microorganisms were 

 studied using a biological model including three indicator 

 strains of Escherichia coli: E. coli WP-2 (a wild strain that 

 retains its unchanged complete gene pool). E. coli Pol A- (a 

 strain that is unable to synthesize one of the enzymes responsible 

 for DNA reparation [DNA polymerase 1 ] ), and E. coli Rec- (a 

 strain that lacks a recombination system, specified by 

 conjugation [Slater e? a/., 1971]). 



Growth suppression of genetically altered strains E. coli 

 Pol A- and E. coli Rec- to a genotoxic effect of the substrate 

 under study was accepted as proof of its carcinogenic activity. 



The pathogenic properties of bacteria strains were assessed 

 using white mice as well the cultures of human embryo kidney 

 cells (RH) and fish skin cells (EPC) (Tsyban, 1988). 



Results and Discussion 



In the process of experimental investigations, data were 

 obtained that characterize the following biological properties 

 pf marine microorganisms: the relation to organic pollutants 

 (e.g.. resistance and degradation ability), resistance to heavy 

 metals, genotoxic and DNA-damaging properties, and 

 pathogenicity. 



Growth of cultures on media containing organic pollutants 

 is defined not only by the cultures' ability to degrade these 

 compounds, but also by their resistance to high concentrations 

 of pollutants. The screening test made it possible to divide the 

 strains of the dominant taxons into three groups: /. resistant to 

 a pollutant and capable of degradation; 2. resistant but not 

 capableofdegradation;andi. sensitive to a pollutant (Table 1 ). 

 The results show that microorganisms isolated from the Bering 

 Sea are rather resistant to the impact of oil and paraffin*. The 

 greatest activity for oil degradation was exhibited by bacteria 

 of the genus Pseudomonas; 72.6% of active cultures occurred 

 among them, and only 6.0% of the strains proved sensitive to 

 oil. In the study of effects of paraffin on the tested strains, it was 

 observed that Bering Sea microorganisms were sensitive and 

 that 28.7% of the investigated strains failed to grow in the 

 presence of paraffin. 



TABLE 1 



Decomposition of petroleum hydrocarbons and paraffin by 



microorganisms of different taxonomic groups isolated from the 



Berina Sea. 



One of the processes occurring in natural microbial 

 populations is microevolution of bacteria, proceeding under 

 the selective pressure of anthropogenic factors. Thus, a variety 

 of microorganisms may develop in their bioresistance to a 

 number of pollutants. 



The mechanism of acquired poly resistance to unfavorable 

 environmental factors is based on the intensive intra- and 

 interspecific exchange of extrachromosomic elements of nuclear 

 material (i.e.. plasmids). The level of this exchange is highest 

 in sewage and may be the same in water bodies having high 

 pollution levels (Baya er al., 1986; Kulskyi ef al.. 1986; Day 

 et al.. 1987; Boominathan el al.. 1988; Gealt, 1988; Lmton, 

 1988; Schmidt & Schlegel, 1989). 



The character and level of antibiotic resistance were 

 studied in representatives of the genera Pseudomo)uis and 

 Bacillus that dominate in the microbial communities of the 

 Bering and Chukchi Seas. MIC of antibiotics, the proportion 

 of sensitive and stable strains, the number of resistance 

 determinants, and the most widespread R-spectra were 

 determined. In the study of R-strain distribution, the strains for 

 which the MIC of an antibiotic exceeded 31.2 |ag/ml (2 |ig/ml 

 for gentamicin), were considered R-strains. 



A common feature of all represented taxonomic groups of 

 Bering Sea microorganisms was the small percentage of strains 

 sensitive to all the antibiotics (0 to 6.3% in different taxonomic 

 groups). The percentage of strains resistant to one antibiotic 

 averaged 24.6%, with a maximum value for the representatives 

 of Bacillus genus (37.5%). Strains resistant to two antibiotics 

 occurred on average 12.0%, with small variations among 

 different taxonomic groups, a range of 8.3-15.6%. Strains 

 resistant to methicillin were most frequent and dominated 

 among the representatives of the genera Pseudomonas and 

 Planococcus (54.2 and 46.5%, respectively). They averaged 

 43.5% (Table 2). 



104 



