Thio Derivatives of 2(5H)-Furanone as Inhibitors against Bacillus subtilis Biofilms.

Gram-positive bacteria cause a wide spectrum of infectious diseases, including nosocomial infections. While in the biofilm, bacteria exhibit increased resistance to antibiotics and the human immune system, causing difficulties in treatment. Thus, the development of biofilm formation inhibitors is a great challenge in pharmacology. The gram-positive bacterium Bacillus subtilis is widely used as a model organism for studying biofilm formation. Here, we report on the effect of new synthesized 2(5H)-furanones on the biofilm formation by B.subtilis cells. Among 57 compounds tested, sulfur-containing derivatives of 2(5H)-furanone (F12, F15, and F94) repressed biofilm formation at a concentration of 10 µg/ml. Derivatives F12 and F94 were found to inhibit the biosynthesis of GFP from the promoter of the eps operon encoding genes of the biofilm exopolysaccharide synthesis (EPS). Using the differential fluorescence staining of alive/dead cells, we demonstrated an increased bacterial sensitivity to antibiotics (kanamycin and chloramphenicol) in the presence of F12, F15, and F94, with F12 being the most efficient one. The derivative F15 was capable of disrupting an already formed biofilm and thereby increasing the efficiency of antibiotics.

[The C-terminus of transcription factor TnrA from Bacillus subtilis controls DNA-binding domain activity but is not required for dimerization].

The transcription factor ThrA, which belongs to the MerR transcription regulators, in Bacillus subtilis cells controls genes of nitrogen metabolism under conditions of nitrogen limitation. As all the DNA-binding proteins, it is present as a dimer in cells, but the dimerization site is still unknown. The multiple alignment of TnrA homologs from the other Bacilli allowed to identify the putative dimerization sites. Using the C-terminal truncated TnrA proteins it is established, that, in contrast to other MerR-proteins, the TnrA C-terminus does not participate in dimerization. The surface plasmon resonance has revealed that C-terminus truncations of TnrA do not inactivate its DNA-binding activity. By contrary, it increased an affinity to DNA, confirming that C-terminus controls the DNA-binding activity in a full-length TnrA.