Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
Collaborative Research Institute for Innovative Microbiology (CRIIM), The University of Tokyo, Tokyo, Japan.
Appl Environ Microbiol. 2023 Mar 29;89(3):e0182222. doi: 10.1128/aem.01822-22. Epub 2023 Feb 15.
spp. are well-known producers of bioactive secondary metabolites (SMs) that serve as pharmaceutical agents. In addition to their ability to produce SMs, spp. have evolved diverse membrane transport systems to protect cells against antibiotics produced by itself or other microorganisms. We previously screened mutants of Streptomyces coelicolor that show a phenotype of reduced undecylprodigiosin (RED) production in a combined-culture with Tsukamurella pulmonis. Here, we identified a point mutation, which reduced RED production, by performing genome resequencing and genetic complementation. We found that inactivation of the gene encoding the TetR family transcriptional regulator (TFR) produced a deficient phenotype for several SMs in Streptomyces coelicolor A3(2). In the genome of S. coelicolor A3(2), two other sets of TFR and two-component ATP-binding cassette (ABC) transporter genes ( and ) were found which had similar effects on the phenotype for both secondary metabolism and antibiotic resistance. An electrophoretic mobility shift assay and quantitative reverse transcription-PCR experiments demonstrated that TFRs repressed the expression of each adjacent two-component ABC transporter genes by binding to the operator sequence. Notably, the Δ mutant showed increased resistance to several antibiotics of other actinomycete origin. Our results imply the switching of cell metabolism to direct offense (antibiotic production) or defense (efflux pump activation) using costly and limited quantities of cell energy sources (e.g., ATP) in the soil ecosystem. The bacterial metabolic potential to synthesize diverse secondary metabolites in the environment has been revealed by recent (meta)genomics of both unculturable and culturable bacteria. These studies imply that bacteria are continuously exposed to harmful chemical compounds in the environment. spp. contain antibiotic efflux pumps and SM biosynthetic gene clusters. However, the mechanism by which soil bacteria, including , survive against toxic compounds in the environment remains unclear. Here, we identified three sets of TFR-ABC transporter genes in Streptomyces coelicolor A3(2). We found that each TFR controlled the expression of respective ABC transporter, and the expression of all ABC transporters negatively impacted SM production and increased antibiotic resistance. Notably, bioinformatic analysis indicated that these TFR-ABC transporter gene sets are highly conserved and widely distributed in the genome of species, indicating the importance of systematic regulation that directs antibiotic production and xenobiotic excretion.
种是众所周知的生物活性次生代谢产物（SMs）的生产者，这些产物可用作药物。除了产生 SMs 的能力外，种还进化出了多样化的膜转运系统，以保护细胞免受自身或其他微生物产生的抗生素的侵害。我们之前筛选了链霉菌中红色素（RED）产量降低的突变体，这些突变体在与 Tsukamurella pulmonis 的混合培养中表现出表型。在这里，我们通过基因组重测序和遗传互补，确定了一个点突变，该突变降低了 RED 的产量。我们发现，编码 TetR 家族转录调节因子（TFR）的基因失活导致链霉菌 A3(2)中几种 SM 的表型缺陷。在链霉菌 A3(2)的基因组中，还发现了另外两组 TFR 和两个二组分 ATP 结合盒（ABC）转运体基因（和），它们对次级代谢和抗生素抗性的表型都有类似的影响。电泳迁移率变动分析和定量逆转录-PCR 实验表明，TFR 通过与操纵子序列结合来抑制每个相邻的二组分 ABC 转运体基因的表达。值得注意的是，Δ突变体对几种来自其他放线菌的抗生素的抗性增加。我们的结果表明，在土壤生态系统中，细胞代谢会利用有限的细胞能量资源（例如 ATP）进行切换，直接进行进攻（抗生素产生）或防御（外排泵激活）。最近对不可培养和可培养细菌的（宏）基因组学研究揭示了细菌在环境中合成多种次生代谢物的代谢潜力。这些研究表明，细菌不断暴露于环境中的有害化合物中。种包含抗生素外排泵和 SM 生物合成基因簇。然而，包括在内的土壤细菌如何在环境中对抗有毒化合物的机制尚不清楚。在这里，我们在链霉菌 A3(2)中鉴定了三组 TFR-ABC 转运体基因。我们发现，每个 TFR 控制各自的 ABC 转运体的表达，所有 ABC 转运体的表达都对 SM 产生和抗生素抗性产生负面影响。值得注意的是，生物信息学分析表明，这些 TFR-ABC 转运体基因簇在种的基因组中高度保守且广泛分布，表明系统调控对抗生素产生和异生物质排泄的重要性。
