Novel Production of Isochainin by a Strain of Streptomyces sp. Isolated from Rhizosphere Soil of the Indigenous Moroccan Plant Argania Spinosa L

Phosphate and potash solubilizing bacteria from Moroccan phosphate mine showing antagonism to bacterial canker agent and inducing effective tomato growth promotion

Most agricultural soils are facing limited phosphorus availability that challenges modern agriculture. Phosphate solubilizing microbia (PSM) has been explored extensively as potential biofertilizers for plant growth and nutrition, and harnessing phosphate rich areas could provide such beneficial microorganisms. Isolation of PSM from Moroccan rock phosphate led to the selection of two bacterial isolates, Bg22c and Bg32c, showing high solubilization potential. The two isolates were also tested for other in vitro PGPR effects and compared to a non-phosphate solubilizing bacterium Bg15d. In addition to phosphates, Bg22c and Bg32c were able to solubilize insoluble potassium and zinc forms (P, K, and Zn solubilizers) and produce indole-acetic acid (IAA). Mechanisms of solubilization involved production of organic acids as demonstrated by HPLC. In vitro, the isolates Bg22c and Bg15d were able to antagonize the phytopathogenic bacteria Clavibacter michiganensis subsp. michiganensis, causal agent of tomato bacterial canker disease. Phenotypic and molecular identification by 16S rDNA sequencing demonstrated delineation of Bg32c and Bg15d as members of the genus Pseudomonas and Bg22c as member of the genus Serratia. The two isolates Bg22c and Bg32c were further tested either alone or in a consortium and compared to the non-P, K, and Zn solubilizing Pseudomonas strain Bg15d for their efficacy to promote tomato growth and yield. They were also compared to treatment with a conventional NPK fertilizer. Under greenhouse conditions, Pseudomonas strain Bg32c remarkably improved the growth of whole plant height, root length, shoot and root weight, number of leaves and fruits, as well as fruit fresh weight. This strain also induced stomatal conductance enhancement. The strain also improved total soluble phenolic compounds, total sugars, protein, phosphorus and phenolic compounds contents compared to the negative control. All increases were more pronounced in plants inoculated with strain Bg32c in comparison with control and strain Bg15d. The strain Bg32c could be considered a potential candidate for formulation of a biofertilizer in order to improve tomato growth.

Genome mining reveals the biosynthetic potential of the marine-derived strain Streptomyces marokkonensis M10

Marine streptomycetes are rich sources of natural products with novel structures and interesting biological activities, and genome mining of marine streptomycetes facilitates rapid discovery of their useful products. In this study, a marine-derived Streptomyces sp. M10 was revealed to share a 99.02% 16S rDNA sequence identity with that of Streptomyces marokkonensis Ap1^T, and was thus named S. marokkonensis M10. To further evaluate its biosynthetic potential, the 7,207,169 bps of S. marokkonensis M10 genome was sequenced. Genomic sequence analysis for potential secondary metabolite-associated gene clusters led to the identification of at least three polyketide synthases (PKSs), six non-ribosomal peptide synthases (NRPSs), one hybrid NRPS-PKS, two lantibiotic and five terpene biosynthetic gene clusters. One type I PKS gene cluster was revealed to share high nucleotide similarity with the candicidin/FR008 gene cluster, indicating the capacity of this microorganism to produce polyene macrolides. This assumption was further verified by isolation of two polyene family compounds PF1 and PF2, which have the characteristic UV adsorption at 269, 278, 290 nm (PF1) and 363, 386 and 408 nm (PF2), respectively. S. marokkonensis M10 is therefore a new source of polyene metabolites. Further studies on S. marokkonensis M10 will provide more insights into natural product biosynthesis potential of related streptomycetes. This is also the first report to describe the genome sequence of S. marokkonensis-related strain.

Date palm and the activated sludge co-composting actinobacteria sanitization potential

The objective of this study was to find a connection between the development of the compost actinobacteria and the potential involvement of antagonistic thermophilic actinomycetes in compost sanitization as high temperature additional role. An abundance of actinobacteria and coliforms during the activated sludge and date palm co-composting is determined. Hundred actinomycete isolates were isolated from the sample collected at different composting times. To evaluate the antagonistic effects of the different recovered actinomycete isolates, several wastewater-linked microorganisms known as human and plant potential pathogens were used. The results showed that 12 isolates have an in vitro inhibitory effect on at least 9 of the indicator microorganisms while only 4 active strains inhibit all these pathogens. The antimicrobial activities of sterilized composting time extracts are also investigated.

Genome sequence and genome mining of a marine-derived antifungal bacterium Streptomyces sp. M10

A marine-derived actinobacteria Streptomyces sp. M10 was identified as a prolific antifungal compounds producer and shared a 99.02 % 16S ribosomal RNA (rRNA) sequence similarity with that of Streptomyces marokkonensis Ap1(T), which can produce polyene macrolides. To further evaluate its biosynthetic potential, the 7,207,169 bp Streptomyces sp. M10 linear chromosome was sequenced and mined for identifiable secondary metabolite-associated gene clusters. A total of 20 secondary metabolite-associated gene clusters were deduced, including three polyketide synthases (PKSs), four non-ribosomal peptide synthetases (NRPSs), four hybrid NRPS-PKSs, three NRPS-independent siderophores, and two lantibiotic and four terpene biosynthetic gene clusters. One of the type I PKS gene cluster, pks1, shared a 85 % nucleotide similarity with candicidin/FR008 gene cluster, indicating the capacity of this organism to produce polyene macrolides. This assumption was verified by a scale-up culturing of Streptomyces sp. M10 on A1 agar plates, which lead to the isolation of two polyene families PF1 and PF2, with characteristic UV adsorption at 269, 278, and 290 nm (PF1) and 363, 386, and 408 nm (PF2), respectively. Compound 9-04 was further purified from PF1, and its chemical structure was partially elucidated to be a typical polyene macrolide by NMR and UV spectrum. This study affirmatively identified Streptomyces sp. M10 as a source of polyene metabolites and highlighted genome mining of interested organism as a powerful tool for natural product discovery.