Molecular profiling and bioinformatics approaches of biofilm formation in ionizing radiation-resistant Bacillus subtilis, isolated from geothermal spring in Ramsar, the North of Iran.

Biofilm formation and its molecular signaling in bacteria resistant to ionizing radiation is not fully understood. This study aimed to investigate the genetic variations and gene expression of biofilm in an ionizing radiation-resistant Bacillus subtilis in Ramsar. Direct sequencing and quantitative PCR were applied to determine nucleotide variations and gene expression profiles of tapA-sipW-tasA, sinR, sinI, ccpA, epsA-O, spoOB, spoOA, slrA, slrR, ymcA and abrB genes. RNAsnp-RNAfold and Phyre2 and the Swiss Model webserver were used to analyze the structural mRNA and protein respectively. At the molecular level, the tapA-sipW-tasA operon was significantly overexpressed and the expression of ccpA and slrR was significantly downregulated. The thermodynamic and ensemble diversity ratio of the tapA (G>C) gene showed the largest changes in RNA secondary structure. In addition, the largest protein pocket belonged to tapA (148.6 A⁰³) compared to the normal structure (121.1 A⁰³). A non-radiation Bacillus subtilis was served as a control group. These results support the hypothesis that the induction of robust biofilm formation is through the (tapA) operon signal in ionizing radiation-resistant B. subtilis and that genetic variation in tapA (G>C) was the major gene associated with diversity in robust biofilm formation.