PT - JOURNAL ARTICLE AU - Camilla M. Kao AU - Nitsara Karoonuthaisiri AU - David Weaver AU - Jonathan A. Vroom AU - Shuning A. Gai AU - Mai-Lan Ho AU - Kedar G. Patel TI - A genomic island of <em>Streptomyces coelicolor</em> harbors the self-contained regulon of an ECF sigma factor AID - 10.1101/247056 DP - 2018 Jan 01 TA - bioRxiv PG - 247056 4099 - http://biorxiv.org/content/early/2018/01/12/247056.short 4100 - http://biorxiv.org/content/early/2018/01/12/247056.full AB - Streptomycetes make up the largest genus of actinobacteria, living predominantly in soil and decaying vegetation. The bacteria are widely known for their filamentous morphologies and their capacity to synthesize antibiotics and other biologically active molecules. More than a decade ago, we and others identified 22 genomic islands that Streptomyces coelicolor M145 possesses and other Streptomyces strains lack. One of these genomic islands, Genomic Island (GI) 6, encodes an extracytoplasmic function (ECF) sigma factor that we were characterizing in separate work. Here we report that artificial induction of the ECF sigma factor, which is encoded by SCO3450, causes the transcription of approximately one-fourth of the genomic island, or ∼26 mostly contiguous genes, to increase. These data suggest that the ECF sigma factor and its regulon are a self-contained transcriptional unit that can be transferred by horizontal gene transfer. To our knowledge, only one other example has been identified of an ECF sigma factor and its contiguous regulon appearing to be transferrable by horizontal gene transfer [18, 19].More than half of the regulon harbored by GI 6 encodes putative enzymes involved in small molecule metabolism. A putative haloacid dehalogenase is present. Genes encoding two putative anti-sigma factors flank SCO3450, the three genes residing within the regulon. The regulon appears not to be induced by the 44 growth conditions recently examined by Byung-Kwan Cho and colleagues [20]. Therefore the regulon appears to confer fitness to S. coelicolor in as-yet unknown situations. The one or more activities required for fitness might range from scavenging to detoxification to communication within microbial communities.