This family of RNA polymerase sigma factors is a member of the Sigma-70 subfamily (TIGR02937). One of these is designated as SigZ in B. subtilis (Swiss_Prot: SIGZ_BACSU). Interestingly, this group has a very sporatic distribution, B. subtilis, for instance, being the only sequenced strain of Bacilli with a member. Dechloromonas aromatica RCB appears to have two of these sigma factors. A member appears on a plasmid found in Photobacterium profundum SS9 and Vibrio fischeri ES114 (where a second one is chromosomally encoded).