Influence of osmolites on dual-species biofilm formation

Abstract. In a large part of ecological niches, bacterial species are united in communities and develop together in the form of heterogeneous structures called biofilms, which are formed on surfaces of different nature and nature with the participation and as a result of the interaction of two or more bacterial species In this study, we evaluated effects of the osmolarity of cultivating on the biofilm development and architecture of biofilms of the bacterium (B. subtilis) during their interactions with Escherichia coli K-12 1655 strain. Effects of the osmolarity of cultivating on bacterial biofilm formation and the mechanisms were analyzed by the crystal violet staining method combined with cultivated microbial analysis and confocal laser scanning microscopy. Тhе increase of the concentration of NaCl in the culture medium over 100 mM leads to inhibition of growth and negatively affects the process of biofilm formation by co-cultivation of B.subtilis 170 and E.coli K-12 1655, B.subtilis 168 and E.coli K- 12 1655 strains. The change of the concentration of NaCl from 100 to 200 mM is accompanied by decrease of the value of the optical density, the average thickness and the relative spread area and proportional increase of the ratio of the spread area of the structures to their volume of the formed biofilms, as well as inhibition of spore formation.