• Korean Journal of Soil Science and Fertilizer
• /
• v.36 no.2
• /
• pp.86-91
• /
• 2003

Carbon material such as graphite and activated charcoal can promote the growth of some formsog bacteria. We examined whether this bacterial growth promoting effect can have a positive influence on field crops. Refined graphite was mixed into the standard soil used in rice cultivation. Varying soil graphite mixtures of 0.1%, 0.5% and 1% were used to cultivate rice seedling for 3 weeks. After transplanting in the filed, rice plants were cultivated for 4 months. To observe the effect of graphite(carbon material) during the cultivation of rice, we examined various different growth components in this research. During the transplanting stage, growth promoting effect of carbon was observed in the 0.1% carbon added soil. However, there were not much difference between graphite added soil and standard soil in the other stages. Rice yield was highest in the soil with 0.1% graphite.

• Molecules and Cells
• /
• v.46 no.10
• /
• pp.637-653
• /
• 2023

The physiology of most organisms, including Drosophila, is heavily influenced by their interactions with certain types of commensal bacteria. Acetobacter and Lactobacillus, two of the most representative Drosophila commensal bacteria, have stimulatory effects on host larval development and growth. However, how these effects are related to host immune activity remains largely unknown. Here, we show that the Drosophila development-promoting effects of commensal bacteria are suppressed by host immune activity. Mono-association of germ-free Drosophila larvae with Acetobacter pomorum stimulated larval development, which was accelerated when host immune deficiency (IMD) pathway genes were mutated. This phenomenon was not observed in the case of mono-association with Lactobacillus plantarum. Moreover, the mutation of Toll pathway, which constitutes the other branch of the Drosophila immune pathway, did not accelerate A. pomorum-stimulated larval development. The mechanism of action of the IMD pathway-dependent effects of A. pomorum did not appear to involve previously known host mechanisms and bacterial metabolites such as gut peptidase expression, acetic acid, and thiamine, but appeared to involve larval serum proteins. These findings may shed light on the interaction between the beneficial effects of commensal bacteria and host immune activity.

• Journal of Microbiology and Biotechnology
• /
• v.30 no.5
• /
• pp.668-680
• /
• 2020

Bacillus velezensis is an important plant growth-promoting rhizobacterium with immense potential in agriculture development. In the present study, Bacillus velezensis Lle-9 was isolated from the bulbs of Lilium leucanthum. The isolated strain showed antifungal activities against plant pathogens like Botryosphaeria dothidea, Fusarium oxysporum, Botrytis cinerea and Fusarium fujikuroi. The highest percentage of growth inhibition i.e., 68.56±2.35% was observed against Fusarium oxysporum followed by 63.12 ± 2.83%, 61.67 ± 3.39% and 55.82 ± 2.76% against Botrytis cinerea, Botryosphaeria dothidea, and Fusarium fujikuroi, respectively. The ethyl acetate fraction revealed a number of bioactive compounds and several were identified as antimicrobial agents such as diketopiperazines, cyclo-peptides, linear peptides, latrunculin A, 5α-hydroxy-6-ketocholesterol, (R)-S-lactoylglutathione, triamterene, rubiadin, moxifloxacin, 9-hydroxy-5Z,7E,11Z,14Z-eicosatetraenoic acid, D-erythro-C18-Sphingosine, citrinin, and 2-arachidonoyllysophosphatidylcholine. The presence of these antimicrobial compounds in the bacterial culture might have contributed to the antifungal activities of the isolated B. velezensis Lle-9. The strain showed plant growth-promoting traits such as production of organic acids, ACC deaminase, indole-3-acetic acid (IAA), siderophores, and nitrogen fixation and phosphate solubilization. IAA production was accelerated with application of exogenous tryptophan concentrations in the medium. Further, the lily plants upon inoculation with Lle-9 exhibited improved vegetative growth, more flowering shoots and longer roots than control plants under greenhouse condition. The isolated B. velezensis strain Lle-9 possessed broad-spectrum antifungal activities and multiple plant growth-promoting traits and thus may play an important role in promoting sustainable agriculture. This strain could be developed and applied in field experiments in order to promote plant growth and control disease pathogens.

• The Plant Pathology Journal
• /
• v.28 no.1
• /
• pp.20-31
• /
• 2012

Endophytic bacterial communities of tidal flat plants antagonistic to oomycete plant pathogens were studied by the isolation of 256 root colonizing endophytic bacteria from surface-disinfected root tissues of six plants ($Rosa$ $rugosa$, $Suaeda$ $maritima$, $Vitex$ $rotundifolia$, $Carex$ $scabrifolia$, $Glehnia$ $littoralis$ and $Elymus$ $mollis$) growing in a tidal flat area of Namhae Island, Korea. To understand the antagonistic potential, an $in$ $vitro$ antagonistic assay was performed to characterize and identify strains that were antagonistic to the oomycete plant pathogens $Phytophthora$ $capsici$ and $Pythium$ $ultimum$ from the total population. Nine percent of the total number of isolated bacteria exhibited in vitro inhibitory activity against target plant pathogenic oomycetes. Taxonomic and phylogenetic placement of the antagonistic bacteria was investigated by analysis of the 16S rRNA gene sequences. The sequence analysis classified the antagonistic strains into four major classes of the domain bacteria ($Firmicutes$, ${\alpha}-Proteobacteria$, ${\gamma}-Proteobacteria$ and $Actinomycetes$) and 10 different genera. Further production of secondary metabolites, hydrolytic enzymes and plant growth promoting traits were determined for the putative new species of antagonistic endophytic bacteria. These new strains could not be identified as known species of ${\alpha}-Proteobacteria$, and so may represent novel bacterial taxa. The unexpected high antagonistic bacterial diversity associated with the tidal flat plants may be indicative of their importance in tidal flat plants as a promising source of novel antimicrobial compounds and biocontrol agents.

• Microbiology and Biotechnology Letters
• /
• v.49 no.2
• /
• pp.217-224
• /
• 2021

Rice blast caused by Pyricularia oryzae, which is a major threat to food security worldwide, markedly decreases the yield of rice. Some rhizobacteria called 'plant growth-promoting rhizobacteria' inhibit plant pathogens and improve plant growth by secreting iron-chelating siderophores. The decreased availability of iron adversely affects the survival of pathogens, especially fungal pathogens, in the rhizosphere. This study aimed to determine the morphological diversity of siderophore-producing bacteria, analyze the type of siderophores produced by the bacteria, and examine their growth-inhibitory activity against Pyricularia oryzae. The rhizobacteria were isolated from the rhizosphere of Sembada Hitam variety of black rice plants in Pakem, Sleman, Yogyakarta, Indonesia. In total, 12 distinct isolates were screened for the production of siderophores. It was found that 9 out of 12 bacteria produced siderophore and most of them were Gram positive bacteria. The best siderophore-producing isolates with different type of siderophore were used in further studies. The IS3 and IS14 isolates were found to be the best siderophore producer that produced hydroxamate and mixed type of hydroxamate-carboxylate type of siderophore, respectively. In the dual culture assay, IS14 showed a strong antagonistic effect against Pyricularia oryzae by the 81.17% inhibition.

• Journal of Applied Biological Chemistry
• /
• v.55 no.2
• /
• pp.129-133
• /
• 2012

To exploit plant growth promoting bacteria in the roots of Miscanthus sacchariflorus, a biomass energy crop, total 64 bacteria were isolated. For the investigation of plant growth promoting effects from the isolated bacteria, production of indole acetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activities were tested and other cultural conditions were examined. As results, 8 isolates showed plant growth promoting effects on the M. sacchariflorus and an isolate designated Agrobacterium sp. BE516 has the highest activity by enhancing the shoot elongation over 2-fold than the control. Agrobacterium sp. BE516 produced 64 ${\mu}g$ IAA per mL and showed ACC deaminase activity which is involved in the resistance to environmental stress such as high salt and drought. It could grow at low temperature in the range from 4 to $15^{\circ}C$, at pH 4.0 and at 4% NaCl. These results indicate that the Agrobacterium sp. BE516 can be useful as a bio-fertilizer for M. sacchariflorus under the stressed conditions.

• Journal of Microbiology and Biotechnology
• /
• v.28 no.7
• /
• pp.1156-1167
• /
• 2018

The aim of this study was to isolate and characterize lead (Pb)-solubilizing bacteria from heavy metal-contaminated mine soils and to evaluate their inoculation effects on the growth and Pb absorption of Brassica juncea. The isolates were also evaluated for their plant growth-promoting characteristics as well as heavy metal and salt tolerance. A total of 171 Pb-tolerant isolates were identified, of which only 15 bacterial strains were able to produce clear haloes in solid medium containing PbO or $PbCO_3$, indicating Pb solubilization. All of these 15 strains were also able to dissolve the Pb minerals in a liquid medium, which was accompanied by significant decreases in pH values of the medium. Based on 16S rRNA gene sequence analysis, the Pb-solubilizing strains belonged to genera Bacillus, Paenibacillus, Brevibacterium, and Staphylococcus. A majority of the Pb-solubilizing strains were able to produce indole acetic acid and siderophores to different extents. Two of the Pb-solubilizing isolates were able to solubilize inorganic phosphate as well. Some of the strains displayed tolerance to different heavy metals and to salt stress and were able to grow in a wide pH range. Inoculation with two selected Pb-solubilizing and plant growth-promoting strains, (i.e., Brevibacterium frigoritolerans YSP40 and Bacillus paralicheniformis YSP151) and their consortium enhanced the growth and Pb uptake of B. juncea plants grown in a metal-contaminated soil. The bacterial strains isolated in this study are promising candidates to develop novel microbe-assisted phytoremediation strategies for metal-contaminated soils.

• Korean Journal of Agricultural Science
• /
• v.43 no.1
• /
• pp.100-108
• /
• 2016

An auxin-producing bacteria (strain 5-1) was isolated from button mushroom compost in Boryeong-Si, Chungcheongnam-Do. The 5-1 strain was classified as a novel strain of Enterobacter aerogenes based on chemotaxonomic and phylogenetic analyses. The isolated E. aerogenes 5-1 was confirmed to produce indole-3-acetic acid (IAA), one of the auxin hormones, using TLC and HPLC analyses. When the concentration of IAA was assessed by performing HPLC quantitative analysis, a maximum concentration of IAA of $109.9mgL^{-1}$ was detected in the culture broth incubated in R2A medium containing 0.1% L-tryptophan for 24 h at $35^{\circ}C$. Acidification of the culture was deemed caused by an increase of IAA because a negative relationship between IAA production and pH was observed. Supplementation with a known precursor of IAA production, L-tryptophan, appeared to induce maximal production at 0.1% concentration, but it reduced production at concentrations above 0.2%. To investigate the growth-promoting effects to crops, the culture broth of E. aerogenes 5-1 was used to inoculate water cultures and seed pots of mung bean and lettuce. In consequence, adventitious root induction and root growth of mung bean and lettuce were two times higher than those of the control.

• KSBB Journal
• /
• v.30 no.3
• /
• pp.97-102
• /
• 2015

This study aimed to evaluate the potential plantgrowth promoting effects of potassium polyacrylate, a superabsorbent polymer, and Bacillus sp. SH1RP8, a family of plant-growth-promoting bacteria. Potassium polyacrylate was selected as the polymer for use due to its high molecular weight and its ability to retain and continuously supply moisture. Plant-growth-promoting rhizobacteria (PGPR) were isolated from the soil and applied to plants growing in dry environments, such as saline conditions. The moisture absorption and retention abilities of potassium polyacrylate were evaluated at a high temperature ($50^{\circ}C$) and in a dry condition, during which time the polymer showed a water retention potential of 19606.07% after 29 days. To overcome the reaming problem in the soil environment, natural polymers (such as cellulose) were mixed with the potassium acrylate. The shoot growths of Peucedanum japonicum Thunb and Arundo donax were significantly enhanced when treated with the mixture of the isolated rhizosphere bacterium SH1RP8 and potassium polyacrylate (63.5 and 124.3%, respectively).

• Journal of Applied Biological Chemistry
• /
• v.66
• /
• pp.394-403
• /
• 2023

In the pursuit of sustainable and environmentally-friendly agricultural practices, we conducted an extensive study on the rhizosphere bacteria inhabiting soils that have been devoid of chemical fertilizers for an extended period exceeding 40 years. Through this investigation, we isolated a total of 80 species of plant growth-promoting rhizosphere bacteria and assessed their potential to enhance plant growth. Among these isolates, Burkholderia cepacia CD2 displayed remarkable plant growth-promoting activity, making it an optimal candidate for further analysis. Burkholderia cepacia CD2 exhibited a range of beneficial characteristics conducive to plant growth, including phosphate solubilization, siderophore production, denitrification, nitrate utilization, and urease activity. These attributes are well-known to positively influence the growth and development of plants. To validate the taxonomic classification of the strain, 16S rRNA gene sequencing confirmed its placement within the Burkholderia genus, providing further insights into its phylogenetic relationship. To delve deeper into the potential mechanisms underlying its plant growth-promoting properties, we sought to confirm the presence of specific genes associated with plant growth promotion in CD2. To achieve this, whole genome sequencing (WGS) was performed by Plasmidsaurus Inc. (USA) utilizing Oxford Nanopore technology (Abingdon, UK). The WGS analysis of the genome of CD2 revealed the existence of a subsystem function, which is thought to be a pivotal factor contributing to improved plant growth. Based on these findings, it can be concluded that Burkholderia cepacia CD2 has the potential to serve as a microbial fertilizer, offering a sustainable alternative to chemical fertilizers.