Microbial Community Structure and its Biofilm Forming Capacity in Wetland Soils, Southern Bulgaria

The aim of this study was to determine the current microbiological status of the microbial communities and their ability to form biofilms in two protected by Natura 2000 wetlands in Southern Bulgaria. The numbers of heterotrophic bacteria (TVC22 and TVC 37), actinomycetes, fungi, and sanitary state indicators were determined for dry soil samples and sediments collected form Zlato pole wetland and Tsalapitsa rice paddies. The number of heterotrophic microorganisms (TVC22 and TVC 37) and indicators of sanitary status (FS, FC, and Escherichia coli) in the two rice paddies near the city of Plovdiv is higher in comparison to the control zone Zlato pole – the maximum was recorded in the rice paddy near Tsalapitsa village (C1 and C2 was 12.6х106 cfu.g-1 and 26х106 cfu.g-1, respectively). In the studied samples, the bacterial complex takes a dominant position and it exceeds the number of both fungus and actinomycetes at least 1.5 times. The cluster analysis showed a high similarity between the soils surrounding the paddy fields and separated sediment from Zlato pole (ZP2) because of the lowest organic load. The biofilm formation capability of the soil microbial communities was tested in vitro and measured using the dye crystal violet (CV). The development of the biofilm was analyzed for seven days in four different nutrient mediums. Results showed better biofilm growth on R2A media for all stations. Our data showed a good correlation between the structure of microbial communities and biofilm-forming capacity.