We cloned and sequenced 8.3 kb of Bacillus subtilis DNA corresponding to theflaA locus involved in flagellar biosynthesis, motility, and chemotaxis. The DNA sequence revealed the presence of 10 complete and 2 incomplete open reading frames. Comparison of the deduced amino acid sequences to data banks showed similarities of nine of the deduced products to a number of proteins of Escherichia coli and Salmonella typhimurium for which a role in flagellar functioning has been directly demonstrated. In particular, the sequence data suggest that theflaA operon codes for the M-ring protein, components of the motor switch, and the distal part of the basal-body rod. The gene order is remarkably similar to that described for region III of the enterobacterial flagellar regulon. One of the open reading frames was translated into a protein with 48% amino acid identity to S. typhimurium Fliu and 29% identity to the 0 subunit of E. coli ATP synthase.Many bacterial species swim actively by means of flagella. Swimming tends to move the bacteria towards attractants and away from repellents. The flagellar organelle is made of three parts: the basal body, the hook, and the filament, with more than 10 different proteins involved in flagellar formation. In addition, there are the motor apparatus and the switch, necessary for rotation of the flagellar filaments and control of the sense (clockwise or counterclockwise) of rotation. A number of sensory elements and components for transduction of the signal to the motor switch are also part of the motility system. A considerable body of data is available regarding the structure and functioning of the flagella of Escherichia coli and Salmonella typhimurium (reviewed in references 21 and 22).About the gram-positive bacterium Bacillus subtilis much less is known. A limited number of mutants affected in motility have been isolated, and a few have been characterized (8, 32). More advanced are the studies related to the chemotactic mechanisms that operate in B. subtilis. A large number of mutants defective in chemotaxis have been isolated, 21 different complementation groups have been identified, and part of a chemotactic locus has been cloned (28, 29). Better knowledge of the genes and gene products of B. subtilis involved in flagellar assembly, motility, and taxis seemed desirable in view of the fact that B. subtilis is a gram-positive bacterium and that its chemotactic response is more complex than that of E. coli (37). From a B. subtilis chromosomal DNA library in XCharon 4A (5) we have isolated one clone that contains the wild-type alleles of two known flaA mutations, flaA4 and flaA15 (9).In this report, we describe the nucleotide sequence of 8,302 contiguous nucleotides of the flaA locus. Insertional inactivation with integrative plasmids showed that the region sequenced is part of a single operon involved in motility (10, 44). Nine of the deduced gene products show similarity to E. coli and S. typhimurium proteins known to be involved in * Corresponding author. flagellar structures and fu...

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Deoxyribonucleic acid is released into the growth medium by Bacillus subtilis at the time of competence. This DNA is enriched for the genetic markers which have previously been demonstrated to be elevated in membrane-DNA preparations and more recently in cell wall-DNA complexes. Furthermore, the purA16/leu-8 relative marker enrichment varies with time, reaching its highest point at the time of maximal competence. Enrichment remains elevated for at least 60 min further in the competence regimen. Thr results suggest that certain genetic markers of the B. subtilis chromosome are preferentially more available to the external medium as the development of competence proceeds.