RESUMO
Streptomyces and related bacteria produce a wide variety of secondary metabolites. Of these, many compounds have industrial applications, but the question of why this group of microorganism produces such various kinds of biologically active substances has not yet been clearly answered. Here, we overview the results from our studies on the novel function and role of Streptomyces metabolites. The diverged action of negative and positive influences onto the physiology of various microorganisms infers the occurrence of complex microbial interactions due to the effect of small molecules produced by Streptomyces. The interactions may serve as a basis for the constitution of biological community.
Assuntos
Interações Microbianas , Streptomyces/metabolismo , Animais , Humanos , Metabolismo SecundárioRESUMO
We screened for a gene that inhibits streptomycin production in Streptomyces griseus when it is introduced on a high-copy-number plasmid pIJ702, and obtained a plasmid pKM545. The introduction of pKM545 abolished streptomycin production on all media tested including YMP-sugar and Nutrient broth. S1 protection analysis demonstrated that the introduction of this plasmid downregulated the transcriptional activity of the promoter preceding strR, the pathway-specific transcriptional regulator for streptomycin biosynthesis. The 2.8-kb BamHI fragment cloned onto pKM545 contained two coding sequences SGR_5442 and 5443. These coding sequences and the two downstream ones (SGR_5444 and 5445) constituted a possible operon structure designated to be rspABCD (regulation of streptomycin production). RspB and RspC exhibited a marked similarity with an ATP-binding domain and a membrane-associating domain of an ABC-2 type transporter, respectively, suggesting that the Rsp proteins comprise a membrane exporter. The gene cluster consisting of the rsp operon and the upstream divergent small coding sequence (SGR_5441) was widely distributed to Streptomyces genome. An rspB mutant of S. griseus produced 3-fold streptomycin of the parental strain in YMP liquid medium. The evidence implies that the Rsp translocator is involved in the export of a substance that specifies the expression level of streptomycin biosynthesis genes in S. griseus.
Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Streptomyces griseus/genética , Streptomyces griseus/metabolismo , Estreptomicina/biossíntese , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Clonagem Molecular , Ordem dos Genes , Loci Gênicos , Mutação , Plasmídeos/genética , Domínios e Motivos de Interação entre ProteínasRESUMO
Widespread interspecific stimulation of antibiotic production occurs in strains of Streptomyces owing to the activity of diffusible substances, as previously determined in our investigations of the cross-feeding effect. In this study, we newly isolated a substance produced by a Streptomyces strain closely related to Streptomyces scabrisporus, based on the observation that this substance induced the production of an unknown antibiotic in another strain related to Streptomyces griseorubiginosus. This substance, named promomycin, is a polyether structurally related to lonomycin. Promomycin itself had an antibiotic activity, but it stimulated antibiotic production in multiple Streptomyces strains at sub-inhibitory concentrations. Evidence implies that this stimulation effect is widespread within this group of bacteria.