Streptomyces mahasarakhamensis sp. nov., an Endophytic Actinobacterium Isolated from Jasmine Rice and its Potential as plant Growth Promoter.

Two endophytic actinobacteria, strains MK5T and MK7, were isolated from the surface-sterilized root of Jasmine rice (Oryza sativa KDML 105). These strains were aerobic actinobacteria with a well-developed substrate and aerial mycelia that formed spiral spore chains. The type strains that shared the high 16S rRNA gene sequence similarity with both strains were Streptomyces naganishii NBRC 12892T (99.4%), "Streptomyces griseicoloratus" TRM S81-3T (99.2%), and Streptomyces spiralis NBRC 14215T (98.9%). Strains MK5T and MK7 are the same species sharing a digital DNA-DNA hybridization (dDDH) value of 95.3% and a 16S rRNA gene sequence similarity of 100%. Chemotaxonomic data confirmed the affiliation of strains MK5T and MK7 to the genus Streptomyces. Strains MK5T and MK7 contained MK-9(H4) as a major menaquinone; the whole-cell sugar of both strains was galactose and glucose. The strain MK5T shared 93.4% average nucleotide identity (ANI)-Blast, 95.5% ANI-MUMmer, 93% average amino acid identity, and 61.3% dDDH with S. spiralis NBRC 14215T. The polyphasic approach confirmed that strain MK5T represents a novel species, and the name Streptomyces mahasarakhamensis sp. nov. is proposed. The type strain is MK5T (= TBRC 17754 = NRRL B-65683). Genome mining, using an in silico approach and searching biosynthesis gene clusters of strains MK5T and MK7, revealed that the genomes contained genes encoding proteins relating to plant growth promotion, bioactive compounds, and beneficial enzymes. Strains MK5T and MK7 could produce indole acetic acid and solubilize phosphate in vitro.

Two novel pyrene-degrading Diaphorobacter sp. and Pseudoxanthomonas sp. isolated from soil.

Two new bacterial strains, KOTLB and RN402, which have the ability to utilize pyrene as their sole source of carbon and energy, were isolated from soil. Strains KOTLB and RN402 degraded 99% of 100 mg/l of pyrene in liquid cultures within 16 days. Besides pyrene, both strains also degraded 100 mg/l of phenanthrene almost completely within 8 days and degraded 99% and 55% of 100 mg/l of fluoranthene within 24 days, respectively. 16S rDNA-based phylogenetic analysis suggested that strains KOTLB and RN402 were Diaphorobacter sp. and Pseudoxanthomonas sp., respectively. These two genera have never been reported to be involved in pyrene degradation. Polymerase chain reaction (PCR) amplification with nidA-specific primers revealed the presence of a dioxygenase gene in both strains. The partial nidA gene products of both strains (317 and 384 amino acids, respectively) exhibited 99-100% identity to the NidA proteins, which are the large subunit of terminal dioxygenases for pyrene degradation of Mycobacterium spp. In addition, PCR further demonstrated that nidA genes of these strains were located on a megaplasmid. This is the first report showing that pyrene-degrading Gram-negative bacteria harbor the nidA gene.