gamma-actinorhodin and actinorhodin

Streptomyces coelicolor is a prolific producer of natural products and serves as a model organism for their study. It produces several pigmented antibiotics, the best-studied of which are the actinorhodins. We used a combination of liquid chromatography-mass spectrometry (LC-MS) and computational tools used for annotating the detected species (e. g., spectral matching, in-silico predictors, molecular networking) to identify putative new actinorhodin analogs. These studies led to the discovery of the first trimeric benzoisochromanequinone, θ-actinorhodin (1). Further metabolomics analysis revealed that the relative amounts of shunt products produced were similar between the two growth conditions explored. This suggests that, while substantially different products were being produced, the biosynthetic gene clusters were similarly active. Overall, this work describes the discovery of the first trimeric benzoisochromanequinone and explores the biosynthetic processes that might lead to its production by metabolomics analysis of relevant intermediates.

Topics: Anthraquinones; Anti-Bacterial Agents; Metabolomics; Streptomyces coelicolor

A strategy based on bidirectional Dötz benzannulation and the oxa-Pictet-Spengler reaction toward the synthesis of actinorhodin and γ-actinorhodin has been explored. This work has resulted in the synthesis of deoxyactinorhodin and deoxy-γ-actinorhodin. The latter is a regioisomer of crisamicin A (which has 10,10'-dihydroxy groups).

Topics: Anthraquinones; Cyclization; Lactones; Naphthoquinones; Stereoisomerism; Streptomyces coelicolor

Streptomyces are ubiquitous soil bacteria well known for their ability to produce a wide range of secondary metabolites including antibiotics. In their natural environments, they co-exist and interact with complex microbial communities and their natural products are assumed to play a major role in mediating these interactions. Reciprocally, their secondary metabolism can be influenced by the surrounding microbial communities. Little is known about these complex interactions and the underlying molecular mechanisms. During pairwise co-culture experiments, a fluorescent Pseudomonas, Pseudomonas fluorescens BBc6R8, was shown to prevent the production of the diffusible blue pigment antibiotic γ-actinorhodin by Streptomyces coelicolor A3(2) M145 without altering the biosynthesis of the intracellular actinorhodin. A mutant of the BBc6R8 strain defective in the production of gluconic acid from glucose and consequently unable to acidify the culture medium did not show any effect on the γ-actinorhodin biosynthesis in contrast to the wild-type strain and the mutant complemented with the wild-type allele. In addition, when glucose was substituted by mannitol in the culture medium, P. fluorescens BBc6R8 was unable to acidify the medium and to prevent the biosynthesis of the antibiotic. All together, the results show that P. fluorescens BBc6R8 impairs the biosynthesis of the lactone form of actinorhodin in S. coelicolor by acidifying the medium through the production of gluconic acid. Other fluorescent Pseudomonas and the opportunistic pathogen Pseudomonas aeruginosa PAO1 also prevented the γ-actinorhodin production in a similar way. We propose some hypotheses on the ecological significance of such interaction.

Topics: Anthraquinones; Anti-Bacterial Agents; Antibiosis; Coculture Techniques; Culture Media; Gluconates; Glucose; Hydrogen-Ion Concentration; Lactones; Mannitol; Mutation; Pseudomonas; Pseudomonas aeruginosa; Pseudomonas fluorescens; Streptomyces coelicolor

The occurrence of poly-3-hydroxybutyric acid (PHB) in 12 different strains of the genus Streptomyces was investigated. Gas chromatographic estimation indicated that all the strains produced PHB and the range of maximum PHB accumulation was between 1.5 and 11.8% dry cell weight. PHB was isolated from Streptomyces coelicolor A3(2) M145 and characterized using Fourier transform-infrared (FT-IR) spectroscopy. The correlation between PHB utilization and antibiotic production in S. coelicolor A3(2) M145, was studied; results indicated a possible role of PHB as a carbon reserve material used for antibiotic production.

Topics: Anthraquinones; Anti-Bacterial Agents; Chromatography, Gas; Hydroxybutyrates; Lactones; Mycelium; Polyesters; Prodigiosin; Statistics as Topic; Streptomyces; Time Factors

The genetically well-known strain Streptomyces coelicolor A3(2) produces the pH indicator (red/blue) antibiotic actinorhodin, but not all the "blue pigment" produced by this strain is actinorhodin. When the organism was subjected to various nutrient limitations (ammonium, nitrate, phosphate, or trace elements), and also during growth cessation caused by a relatively low medium pH, blue pigment production was initiated but the pigment and its location varied. At pH 4.5 to 5.5, significant formation of actinorhodin occurred and was located exclusively intracellularly. At pH 6.0 to 7.5 a different blue pigment was produced intracellularly as well as extracellularly. It was purified and identified as gamma-actinorhodin (the lactone form of actinorhodin). Analysis of act mutants of S. coelicolor A3(2) confirmed that both pigments are derived from the act biosynthetic pathway. Mutants with lesions in actII-ORF2, actII-ORF3, or actVA-ORF1, previously implicated or suggested to be involved in actinorhodin export, were impaired in production of gamma-actinorhodin, suggesting that synthesis of gamma-actinorhodin from actinorhodin is coupled to its export from the cell. However, effects on the level of actinorhodin production were also found in some mutants.

Topics: Anthraquinones; Anti-Bacterial Agents; Biological Transport; Hydrogen-Ion Concentration; Lactones; Mutation; Pigments, Biological; Spectrophotometry; Streptomyces