A novel plant growth-promoting rhizobacterium, Rhizosphaericola mali gen. nov., sp. nov., isolated from healthy apple tree soil

Abstract

The rhizosphere microbial community is closely associated with plant disease by regulating plant growth, agricultural production, nutrient availability, plant hormone and adaptation to environmental changes. Therefore, it is very important to identify the rhizosphere microbes around plant roots and understand their functions. While studying the differences between the rhizosphere microbiota of healthy and diseased apple trees to find the cause of apple tree disease, we isolated a novel strain, designated as B3-10T, from the rhizosphere soil of a healthy apple tree. The genome relatedness indices between strain B3-10T and other type species of family Chitinophagaceae were in the ranges of 62.4–67.0% for ANI, 18.6–32.1% for dDDH, and 39.0–56.6% for AAI, which were significantly below the cut‑off values for the species delineation, indicating that strain B3-10T could be considered to represent a novel genus in family Chitinophagaceae. Interestingly, the complete genome of strain B3-10T contained a number of genes encoding ACC-deaminase, siderophore production, and acetoin production contributing to plant-beneficial functions. Furthermore, strain B3-10T was found to significantly promote the growth of shoots and roots of the Nicotiana benthamiana, which is widely used as a good model for plant biology, demonstrating that strain B3-10T, a rhizosphere microbe of healthy apple trees, has the potential to promote growth and reduce disease. The phenotypic, chemotaxonomic, phylogenetic, genomic, and physiological properties of this plant growth-promoting (rhizo)bacterium, strain B3-10T supported the proposal of a novel genus in the family Chitinophagaceae, for which the name Rhizosphaericola mali gen. nov., sp. nov. (= KCTC 72123T = NBRC 114178T).

Bacillus megaterium: Evaluation of Chemical Nature of Metabolites and Their Antioxidant and Agronomics Properties

“…A total of 75 compounds were found to be present in BC extracts and not present in CS2 extracts, as illustrated in Table 3 for analysis without derivatization, and in Table 4 for analysis with derivatization. Some of these identified compounds were strictly found in BC extracts, suggesting a probable production by B. megaterium: 10 fatty acids derivatives (23 ′ , 32 ′ , 34 ′ , 39 ′ , 42 ′ , 44 ′ , 46 ′ , 47 ′ , 36, 44), 5 linear hydrocarbons (4,12,20,24,25), 5 cyclic hydrocarbons with 3 isomers (5,6,8,9,10,11,15,18), 6 amino acids (10 ′ , 12 ′ , 15 ′ , 18 ′ , 20 ′ , 22 ′ ), 2 dipeptides (29, 47), 2 cyclic dipeptides (46, 64), 6 aromatic hydrocarbons (1,16,26,27,31,33), 2 phthalates (59, 61), 2 sugar acids with 1 isomer (9 ′ , 24 ′ , 41 ′ ), 4 polyols with 1 isomer (2 ′ , 4 ′ , 5 ′ , 6 ′ , 21 ′ ), 2 cyclitols (29 ′ , 43 ′ ) and 17 others were identified (3,7,13,14,19,21,23,32,37,43,45,48,50,62, 63, 17 ′ , 38 ′ ). tr indicates integration inferior to 0.1 × 10 6 ; "ND": not detected.…”

“…Thus, natural organisms, especially microorganisms like bacteria, still remain the richest and biggest source for new biocontrol or antimicrobial agents and have emerged as a promising alternative to chemical compounds [5][6][7]. There is a large body of literature reporting the potential use of rhizosphere-associated bacteria with a positive effect on the growth, development or health of plants [8,9]. Under specific environment conditions, plant growth-promoting rhizobacteria (PGPR) can enhance the productivity of field crops, and some species are actually already commercialized for their direct inoculation in soil [10].…”