Enhancement of oxytetracycline production after gamma irradiation-induced mutagenesis of Streptomyces rimosus CN08 strain

Genome-guided approaches and evaluation of the strategies to influence bioprocessing assisted morphological engineering of Streptomyces cell factories

Streptomyces genera serve as adaptable cell factories for secondary metabolites with various and distinctive chemical structures that are relevant to the pharmaceutical industry. Streptomyces' complex life cycle necessitated a variety of tactics to enhance metabolite production. Identification of metabolic pathways, secondary metabolite clusters, and their controls have all been accomplished using genomic methods. Besides this, bioprocess parameters were also optimized for the regulation of morphology. Kinase families were identified as key checkpoints in the metabolic manipulation (DivIVA, Scy, FilP, matAB, and AfsK) and morphology engineering of Streptomyces. This review illustrates the role of different physiological variables during fermentation in the bioeconomy coupled with genome-based molecular characterization of biomolecules responsible for secondary metabolite production at different developmental stages of the Streptomyces life cycle.

Gamma-induced mutants of Bacillus and Streptomyces display enhanced antagonistic activities and suppression of the root rot and wilt diseases in pulses

This study aims to increase Bacillus and Streptomyces antagonistic activity against the root rot and wilt diseases of pulses caused by Macrophomina phaseolina and Fusarium oxysporum f. sp. udum, respectively. To increase antagonistic action, Bacillus subtilis BRBac4, Bacillus siamensis BRBac21, and Streptomyces cavourensis BRAcB10 were subjected to random mutagenesis using varying doses of gamma irradiation (0.5–3.0 kGy). Following the irradiation, 250 bacterial colonies were chosen at random for each antagonistic strain and their effects against pathogens were evaluated in a plate assay. The ERIC, BOX, and random amplified polymorphic studies demonstrated a clear distinction between mutant and wild-type strains. When mutants were compared to wild-type strains, they showed improved plant growth-promoting characteristics and hydrolytic enzyme activity. The disease suppression potential of the selected mutants, B. subtilis BRBac4-M6, B. siamensisi BRBac21-M10, and S. cavourensis BRAcB10-M2, was tested in green gram, black gram, and red gram. The combined inoculation of B. siamensis BRBac21-M10 and S. cavourensis BRAcB10-M2 reduced the incidence of root rot and wilt disease. The same treatment also increased the activity of the defensive enzymes peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase. These findings suggested that gamma-induced mutation can be exploited effectively to improve the biocontrol characteristics of Bacillus and Streptomyces. Following the field testing, a combined bio-formulation of these two bacteria may be utilised to address wilt and root-rot pathogens in pulses.

Improvement of R-2-(4-hydroxyphenoxy) propionic acid biosynthesis of Beauveria bassiana by combined mutagenesis

R-2-(4-hydroxyphenoxy)propionicacid (HPOPA) is a valuable intermediate for the synthesis of enantiomerically pure aryloxyphenoxypropionic acid herbicides. In this work, to improve the HPOPA biosynthesis by Beauveria bassiana ZJB16002 from the substrate R-2-phenoxypropionic acid (POPA), the original HPOPA producer B. bassiana ZJB16002 was subjected to physical mutagenesis with ¹³⁷ Cs-γ irradiation and chemical mutagen N-methyl-N'-nitro-N-nitrasoguanidine (NTG) induced mutagenesis. The effects of different treatment doses of the mutagens on the lethal rate and positive mutation rate were investigated, and the results showed that the optimal ¹³⁷ Cs-γirradiation dose and NTG concentration was 850 Gy and 500 µg/mL, respectively. Under these conditions, a mutant strain CCN-7 with the highest HPOPA production capacity was obtained through two rounds of ¹³⁷ Cs-γ irradiation treatment followed by one round of NTG mutagenesis. At the substrate (POPA) concentration of 50 g/L, HPOPA titer of CCN-7 reached 36.88 g/L, which was 9.73-fold higher than the parental strain. The morphology of the wild-type and mutant strain was compared and the results might provide helpful information in exploration of the correlation of morphology and biochemical features of B. bassiana.