Possible involvement of bacterial autolytic enzymes in flagellar morphogenesis

Abstract

Autolytic enzymes were required for flagellar morphogenesis in Bacillus subtilis 168 and B. licheniformis 6346. Two previously characterized, poorly lytic, chain-forming mutants of B. subtilis 168, strains FJ3 (temperature conditional) and FJ6, each 90-95% deficient in the production of N-acetylmuramyl-L-alanine amidase and endo-.beta.-N-acetylglucosaminidase, were observed to be nonmotile at 35.degree. C in a variety of liquid and semisolid media. In contrast, cells of the isogenic wild-type strain were motile and fully separated. EM revealed the complete absence of flagella on the mutant cells. Similar observations were made with another poorly lytic strain of B. subtilis 168 (Nil5) and with 2 poorly lytic, phosphoglucomutase-deficient mutants of B. licheniformis 6346 (MH-3, MH-5). In minimal media lacking galactose (restrictive conditions), the B. licheniformis mutants failed to form flagella, or had serious abnormalities in flagellar morphogenesis and motility. Under permissive conditions, mutants FJ3 (grown at 17.degree. C) and MH-5 (grown with added galactose) showed increased autolytic activities, grew in the dechained form, and regained their capacities to synthesize functional flagella. Examination of several classes of spontaneous revertants derived from the various mutant strains further demonstrated a close relationship between autolysin activity and flagellation in the 2 Bacillus spp.