Biofilm Formation Between Bacillus Subtilis and Escherichia Coli K-12 Strains at Acidic and Oxidative Stress

Biofilms constitute the predominant microbial style of life in natural and engineered ecosystems. At the harsh environmental conditions microorganisms accumulate reactive oxygen species (ROS), potentially encountering a dangerous condition called oxidative stress. An investigation into the mechanisms activated by biofilms in response to different oxidative stress levels could have important consequences from ecological and economic points of view, and could be exploited to propose alternative strategies to control microbial virulence and deterioration. In this respect, the aim if this study is to evaluate the influence temperature and pH of the medium, its osmolality and the presence of heavy metal ions on the growth of the biomass of biofilm formed by B. subtilis 170 and E. coli K- 12 strains and their relationship in them. Тhis study was used the methods for a static cultivation of biofilm by co-cultures of B. subtilis 170 and E. coli K- 12 strains and determination of colony forming units in their structures to evaluate of the relationships between them. The results of the present study show that temperature of 20°C and pH-value in the range of 5.0-6.0 help to maximum growth of biomass of biofilm formed by co-cultivation of B. subtilis 170 and E. coli 1655 strains. The competitive relationships are observed at a temperature of 20°C, at pH-value in the range from 5.0 to 6.0 at low osmolality of the medium of 100 to 150 mM, at content of Fe+ 2 from 5 μM to 100 μM. The increase of the temperature above 30°C and the pH of the medium, the high osmolality of 200 mM triggers antagonistic interactions between B. subtilis 170 and E. coli K- 12 strains, while at content of Fe+ 2 of 50 μM was observed symbiosis in the structure of biofilms in this study.