ABSTRACT
Aims@#The objective of this study was to analyze the genome of endophytic actinomycete associated with orchids and evaluate its plant hormone activities, including phytohormone, siderophore, ammonia production, zinc and phosphate solubilization.@*Methodology and results@#Strain DR1-2 isolated from the roots of the Thai orchid, Dendrobium christyanum Rchb.f., was closely related to Pseudonocardia alni DSM 44104T, P. antarctica DSM 44749T and P. carboxydivorans Y8T (99.93-100% similarity) based 16S rRNA gene sequence. This strain exhibited IAA production (294.10 ± 12.17 μg/mL), phosphate solubilization (2.20 ± 0.08 solubilization Index, SI), positive for siderophore production and ammonia production (36.99 ± 2.24 μg/mL). It showed a maximum IAA of 489.73 ± 8.90 μg/mL, when optimized using 0.5% Ltryptophan, pH 6 and incubated at 30 °C for 7 days. The IAA of strain enhanced the root length, shoot length, number of roots and fresh weight of rice seedlings (Oryza sativa L. cv. RD49). The draft genome of strain DR1-2 was 6,077,423 bp in 23 contigs with G+C content of 74.6%. The average nucleotide identity-Blast (ANIb) and average nucleotide identity-MUMmer (ANIm) values of strain DR1-2 and related type strains were 95.81 to 97.25% and the digital DNA-DNA hybridization (dDDH) values were 72.60 to 74.00%, respectively. Genomic analysis of strain DR1-2 revealed that the gene encodes the enzyme involved in the phytohormones biosynthesis and gene clusters involved in the biosynthesis of bioactive metabolites.@*Conclusion, significance and impact of study@#Endophytic actinomycete, Pseudonocardia strain DR1-2 from Thai orchid, D. christyanum Rchb.f., exhibited significant IAA production and affected the growth of the plant, which was the potential source of plant hormones for agricultural applications.
Subject(s)
Endophytes , Actinobacteria , PseudonocardiaABSTRACT
Aims: Isolate and characterize the antimicrobial actinomycetes from sediments of Mangrove ecosystems of Nizampatnam located in the south coastal region of Andhra Pradesh, India. Methodology and Results: The Mangrove soil samples were collected, pre-treated and plated on asparagine-glucose agar medium. Identification of the strain was carried out by employing the polyphasic taxonomical studies including the 16S rRNA sequence based analysis. Phylogenetic tree was constructed using the Molecular Evolutionary Genetic Analysis (MEGA) version 5. The potent bioactive metabolite strain was isolated and designated as VUK-10. Further polyphasic studies revealed that the Isolate VUK-10 belongs to the genera Pseudonocardia. Phylogenetic analysis of 16S rRNA sequencing studies revealed that the strain is closely related to Pseudonocardia endophytica and the bioactive metabolites produced by the isolate inhibited Gram positive, Gram negative and Fungi. Conclusion, significance and impact of study: The isolation, characterization of the rare actinomycetes from the mangrove ecosystem will be useful for the discovery of the novel bioactive metabolites that are effective against wide range of pathogens.
ABSTRACT
The purpose of the present study was to investigate the influence of cultural and environmental parameters affecting the growth and bioactive metabolite production of the rare strain VUK-10 of actinomycete Pseudonocardia, which exhibits a broad spectrum of in vitro antimicrobial activity against bacteria and fungi. Production of bioactive metabolites by the strain was high the in modified yeast extract-malt extract-dextrose (ISP-2) broth, as compared to other tested media. Glucose (1%) and tryptone (0.25%) were found to be the most suitable carbon and nitrogen sources, respectively, for optimum production of growth and bioactive metabolites. Maximum production of bioactive metabolites was found in the culture medium with initial pH 7 incubated with the strain for four days at 30degrees C, under shaking conditions. This is the first report on the optimization of bioactive metabolites by Pseudonocardia sp. VUK-10.