Complete sequence of Bacillus subtilis plasmid p1414 and comparison with seven other plasmid types found in Russian soil isolates of Bacillus subtilis

We determined the complete sequence of a cryptic 7949-bp plasmid isolated f rom naturally occurring Bacillus subtilis found in Russian soil from Moscow . We found 15 putative open reading frames (ORFs), all of which were preced ed by a ribosome binding site. One encodes the gene (rep) which should be e ssential for vegetative rolling circle replication (RCR). The putative doub le-stranded origin as well as a palT1-like single-stranded origin was also identified. The predicted product of another ORF showed similarity to a mob lization protein while a third showed similarity to a ubiquitous family of small proteins whose members have so far been associated with stress respon se. We used fragments with these latter ORFs to probe representatives of se ven other groups of cryptic RCR plasmids from geographically related B. sub tilis isolates. All plasmids carried the mob function, suggesting a common ancestor for the rep/mob region but the putative hsp, was present only on s ome of the plasmids. This suggests that the putative hsp gene is not an ess ential plasmid component and may therefore be present as a phenotypic marke r-perhaps providing response to stress. This adds weight to the growing evi dence that these small Bacillus plasmids may not be cryptic but may provide an adaptive advantage for the host in its natural environment. (C) 1999 Ac ademic Press.