New loci required for Streptomyces coelicolor morphological and physiological differentiation

Abstract

Streptomyces coelwcolor colonies differentiate both morphologically, producing aerial spore chains, and physiologically, producing antibiotics as secondary metabolites. Single mutations, which block both aspects of differentiation, define bld (bald colony) genes. To identify new bld genes, mutagenized colonies were screened for blocks in the earliest stage of sporulation, the formation of aerial mycelia, and blocks in antibiotic synthesis. The mutations in 12 mutants were mapped; in each strain, the pleiotropic phenotype was due to a single mutation. Seven of the strains contained mutations in known bld loci, bidA and bidB. Three strains contained mutations in a new locus, bldG, and two contained mutations in another new locus, bldH. Like the previously defined bldA mutants, the bldG and bldH mutants were developmentally blocked on glucose. On a variety of carbon sources whose utilization was subject to glucose repression, the developmental blocks were partially relieved for bidG (and bldA) mutants and fully relieved for bldH mutants. These results are compatible with an hypothesis which suggests that there are two alternative controls on S. coelicolor differentiation, one of which is glucose repressible.

Carbon source regulation of antibiotic production

“…In this regard, BldB has been characterized as a protein involved in aerial hyphae formation. 114 Interestingly, it has been observed that after rapid growth has ceased, culture supernatants become protein rich, supporting the idea that protein secretion is also a stationaryphase phenomenon. 116 It is known that on different carbon sources, BldB null mutants have a bald phenotype, that is, lacking an obvious aerial mycelium, are pleiotropically blocked for antibiotic biosynthesis 110 and defective in CCR.…”

“…Repression is partially relieved using alternative carbon sources (arabinose, galactose, glycerol, mannitol and maltose) for bldA and bldG mutants and totally relieved for bldH mutants. 114 Therefore, all bld mutants isolated, exhibit carbon source-dependent differentiation.…”

“…In addition to the PTS system, the analysis of Streptomyces mutants insensitive to CCR has suggested the involvement of the products of a number of genes such as bld and reg1 in the mechanism of CCR. 114,115 In S. coelicolor, the synthesis of antibiotic and the formation of aerial hyphae initiate at approximately the same time during microbial development, and there is some evidence suggesting that both events are coordinated at the molecular level. In this regard, BldB has been characterized as a protein involved in aerial hyphae formation.…”

“…116 adpA, also known as bldH, mediates the effects of bldA on morphological differentiation and antibiotic production. 114 With regard to bldG, it has been proposed that this gene encodes a putative anti-anti-sigma factor that might control transcription of both aerial mycelia formation and antibiotic formation. 120 Using transposon mutagenesis, Chouayekh et al 121 isolated S. lividans TK24 mutants the a-amylase expression of which was resistant to glucose catabolite repression.…”

A developmentally regulated Streptomyces endoribonuclease resembles ribonuclease E of Escherichia coli

“…Investigation of RNase E activity in Streptomyces mutants blocked at various stages of development provided further evidence of developmentally regulated genetic control of RNase ES; such mutations have mostly been isolated in S. coelicolor A3(2), which is closely related genetically to S. lividans, and their phenotype effects have been well characterized (Chater, 1993): bld mutants do not produce visible aerial mycelia and are also blocked in their physiological differentiation (Merrick, 1976;Champness, 1988;Chater, 1993); whi mutants cannot make mature spores, yielding S. coelicolor colonies that have a whitish, rather than grey, appearance (Hopwood et al, 1970;Chater, 1972). We studied two S. coelicolor bld mutants [bldA (J1700) (Merrick, 1976;Lawlor et al, 1987), bldC (J660) (Merrick, 1976)] and three whi mutants [whiB (Chater, 1972), whiJ (C77) (Chater, 1989) and whiG (C71) (Chater, 1972)] and their parental strains lacking these mutations ( activity increased in the parental S. coelicolor strains, the three whi mutants studied, and a bldC mutant as these various bacteria progressed through their life cycle in solid media (shown only for whiG, Fig.…”