Biochemical and genetic characterization of the flagellar filaments from the rumen anaerobe Butyrivibrio fibrisolvens OR77

Flagellar filaments isolated from stationary phase cells of the rumen anaer obe Butyrivibrio fibrisolvens OR77 were composed of three flagellins (54, 6 2 and 68kDa). All three proteins demonstrated a conserved N-terminus, with homology to the N-terminus of the flagellin from the intestinal anaerobe Ro seburia cecicola. Two genes encoding flagellins were identified and cloned from the genome of this isolate. Transcriptional analysis indicated that bo th genes were expressed, but as separate unit length messages. The first ge ne (flaA) encoded a flagellin with a predicted molecular weight of 50 kDa. Transcription initiation within the flaA operon occured at two different pr omoter sites. The first promoter demonstrated significant sequence similari ty to the flagellum specific promoter consensus sequence (sigma(28)), the s econd to the general "housekeeping" consensus sequence (sigma(43)). The sec ond flagellin gene (flaB) encoded a flagellin with a predicted molecular we ight of 54 kDa. Differences in the predicted and determined flagellin molec ular weights, the number of flagellins and corresponding genes, and a posit ive reaction using an immunoassay for the detection of digoxigenin labeled sugars, indicate that the flagellins of B. fibrisolvens OR77 undergo post-t ranslational modification in the form of glycosylation.