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Molecular Genetics of Streptomycetes |
Department of Microbiology, Michigan State University, East Lansing, MI 48824-1101, USA1
Author for correspondence: Wendy Champness. Tel: +1 517 353 9770. Fax: +1 517 353 8957. e-mail: champnes{at}pilot.msu.edu
The absA locus in Streptomyces coelicolor A3(2) was identified because mutations in it uncoupled sporulation from antibiotic synthesis: absA mutants failed to produce any of the four antibiotics characteristic of S. coelicolor. These mutants are now shown to contain point mutations in the absA1 gene which encodes the histidine kinase sensor-transmitter protein of a two-component signalling system. The absA1 non-antibiotic-producing mutants, which are unpigmented, spontaneously acquire pigmented colony sectors. Genetic analysis established that the pigmented sectors contain second-site suppressive mutations, sab (for suppressor of abs). Phenotypic characterization showed that sab strains produce all four antibiotics; some overproduce antibiotics and are designated Pha, for precocious hyperproduction of antibiotics. A set of sab mutations responsible for suppression was localized by plasmid-mediated and protoplast fusion mapping techniques to the vicinity of the absA locus. DNA cloned from this region was used to construct phage that could transduce sab mutations. Sequence analysis of sab strains defined sab mutations in both the absA1 gene and the absA2 gene; the latter encodes the two-component systems response regulator.
Keywords: Streptomyces coelicolor, antibiotic biosynthesis and regulation, two-component system, genetic suppression
Abbreviations: Act, actinorhodin; CDA, calcium-dependent antibiotic; Mmy, methylenomycin; NF, normal fertility; Red, undecylprodigiosin; UF, ultra fertility
a Present address: TerraGen Diversity Inc., Vancouver, British Columbia, Canada.
b Present address:Department of Molecular Biology and Microbiology, Tufts University, Boston, MA 02111, USA.
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