A novel actinomycete strain, JA03T, belonging to the genus Streptomyces , was isolated from the rhizosphere of Barringtonia racemosa (L.) Spreng. It was characterized taxonomically using a polyphasic approach. It grew at 25–37 °C, at pH 5–10 and with 6 % (w/v) NaCl. It contained ll-diaminopimelic acid in the cell-wall peptidoglycan. Ribose and glucose were detected in its whole-cell hydrolysate. The predominant cellular fatty acids were iso-C16 : 0, anteiso-C15 : 0, C16 : 0, iso-C14 : 0 and iso-C15 : 0. Detected polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides, unidentified phospholipids and unidentified amino lipids. Based on the results of 16S rRNA gene sequence analyses, strain JA03T showed highest similarity to Streptomyces filipinensis NBRC 12860T (98.76 %), Streptomyces fodineus TW1S1T (98.69 %) and Streptomyces shenzhennensis 172115T (98.68 %). Strain JA03T has a genome size of 9 092 851 bp with DNA G+C content of 71.28 mol%. The average nucleotide identity (ANI)-blast and ANI-MUMmer values of strain JA03T and related type strains were 79.6–89.2 and 86.7–92.5 %, respectively, and the digital DNA–DNA hybridization values were 27.3–46.4 %. Ethyl acetate extract of JA03T exhibited total phenolic content (33.4±0.6 µg mg−1 gallic acid equivalent), ferric reducing power value (70.8±1.8 µg mg−1 ascorbic acid equivalent) and 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity (IC50=67.0±21.1 µg ml−1). Intracellular reactive oxygen species and NO production in RAW264.7 macrophage cells induced by H2O2 and lipopolysaccharide were inhibited with IC50 of 67.40 and 16.95 µg ml−1, respectively. Based on the taxonomic results, it has been concluded that strain JA03T represents a novel species of the genus Streptomyces for which the name Streptomyces barringtoniae sp. nov., is proposed. The type strain is JA03T (=LMG 32415T=TISTR 2999T).

A novel actinomycete, strain SDA37, belonging to the genus Actinomadura, was isolated from rhizosphere soil collected from Udon Thani Province, Thailand. The taxonomic position of the strain was characterized using a polyphasic approach. Meso-diaminopimelic acid, glucose, ribose, galactose and madurose were detected in cell-wall and whole-cell hydrolysates. The N-acyl type of muramic acid was acetyl. Menaquinones were MK-9(H6), MK-9(H8) and MK-9(H4). The predominant cellular fatty acids were iso-C16 : 0, C16 : 0, 10-methyl C18 : 0 and iso-C14 : 0. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol and phosphatidylinositol. blast analysis of the almost-complete 16S rRNA gene sequence showed 98.8 % similarity to Actinomadura oligospora NBRC 104149, 98.7 % similarity to Actinomadura gamaensis DSM 100815 and 97.2 % similarity to Actinomadura rupiterrae KCTC 19559. The DNA G+C content was 73.1 mol%. Strain SDA37 showed low DNA-DNA relatedness (44.3±7.3 to 58.5±8.7 %) to A. oligospora NBRC 104149, Actinomadura gamaensis DSM 100815 and Actinomadura rupiterrae KCTC 19559. The new strain could also be distinguished from its closely related strains by the differences in the phenotypic characteristics. The results of taxonomic analysis suggested that strain SDA37 represented a novel species of the genus Actinomadura for which the name Actinomadura rhizosphaerae sp. nov. is proposed. The type strain is SDA37 (=KCTC 39965=NBRC 112909=TISTR 2523).

Aims: This study aims to isolate, characterize and screen the plant growth-promoting bacteria from Zingiberaceae plants. Plant promoting activities such as indole-3-acetic acid (IAA), phosphate solubilization, zinc solubilization and nitrogen-fixing capabilities are determined, and the IAA production of selected isolates are optimized. Methodology and results: Endophytic bacteria were isolated from the plant samples by surface sterilization on nutrient agar (NA) plates and incubated at 30 °C for 2-3 days. The bacteria were identified based on their phenotypic characteristics and 16S rRNA gene sequence analyses. All isolates were identified as genera Bacillus, Lysinibacillus, Kerstersia, Klebsiella and Brucella. The isolates exhibited phosphate solubilization (1.5 ± 0.75-37.5 ± 8.75 Solubilization Index, SI), zinc solubilization (2.5 ± 0-60 ± 1.5 SI) and IAA production (0.1 ± 0.2-115.7 ± 1.6 µg/mL), while 3 isolates possessed nitrogen-fixing capabilities. Five isolates (PHAS-2, PWS-2, PWR-2, PHBS-2 and SCG-2) were selected for IAA optimization. Isolate PWR-2 produced the maximum IAA at 447.7 ± 0 µg/mL when tryptophan concentration was maintained at 1.0%. Conclusion, significance and impact of study: Genera of bacteria included Bacillus, Lysinibacillus, Kerstersia, Klebsiella and Brucella were successfully isolated from Zingiberaceae plants. All the isolates showed the capability to produce IAA, while some isolates exhibited phosphate solubilization and zinc solubilization, and a few possessed nitrogen-fixing capabilities. The potential IAA production isolates could be applied for the enhancement of agricultural production that will be becoming a more widely accepted practice.