Chitinophaga agri sp. nov., a bacterium isolated from soil of reclaimed land.

A Gram-negative, aerobic, and long rod-shaped bacterium, designated as H33E-04T, was isolated from the soil of reclaimed land, Republic of Korea. The strain grew at a temperature range of 15-40 °C, pH 5.0-10.0, and 0-2% NaCl (w/v). The phylogenetic analysis based on 16S rRNA gene sequences showed that strain H33E-04T was in the same clade with Chitinophaga pinensis DSM 2588T, Chitinophaga filiformis IFO 15056T, and Chitinophaga ginsengisoli Gsoil 052T with 98.4%, 97.9%, and 97.8% sequence similarities, respectively. The de novo genome assembly revealed that the DNA G + C content of the strain was 46.2 mol%. Comparative genome analysis between strain H33E-04T and C. pinensis DSM 2588 T showed that the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values were 79.9% and 23.4%, respectively. The major respiratory quinone was menaquinone-7 (MK-7) and the predominant cellular fatty acids were iso-C15:0 (31.7%), C16:1 ω5c (31.2%), and iso-C17:0 3-OH (11.8%), supporting the affiliation of strain H33E-04T with the genus Chitinophaga. Based on phylogenetic, physiological, and chemotaxonomic characteristics, strain H33E-04T represents a novel species of the genus Chitinophaga, for which the name Chitinophaga agri sp. nov. is proposed. The type strain of Chitinophaga agri is H33E-04T (= KACC 21303T = NBRC114512T).

Arachidicoccus soli sp. nov., a bacterium isolated from soil.

A Gram-stain-negative, aerobic, non-motile and rod-shaped bacterium, designated KIS59-12T, was isolated from a soil sample collected on Hodo island, Boryeong, Republic of Korea. The strain grew at 10-33 °C, pH 6.0-7.5 and with 0-4 % NaCl (w/v). Results of phylogenetic analysis based on 16S rRNA gene sequences showed that strain KIS59-12T was in the same clade as Arachidicoccus rhizosphaerae Vu-144T and Arachidicoccus ginsenosidivorans Gsoil809T with 97.5 and 97.2 % sequence similarity, respectively. Comparative genome analysis between strain KIS59-12T and A. rhizosphaerae Vu-144T showed that average nucleotide identity value was 69.4 % and the digital DNA-DNA hybridization value was 19.1 %. The major respiratory quinone was menaquinone-7. The major polar lipids were phosphatidylethanolamine and an unknown polar lipid. The predominant cellular fatty acids were iso-C15 : 0, iso-C15 : 1 G and iso-C17 : 0 3-OH, which supported the affiliation of strain KIS59-12T with the genus Arachidicoccus. The major polyamines were homospermidine and putrescine. The genomic DNA G+C content was 36.4 mol%. On the basis of phylogenetic, physiological and chemotaxonomic characteristics, strain KIS59-12T represents a novel species of the genus Arachidicoccus, for which the name Arachidicoccus soli sp. nov. is proposed. The type strain of Arachidicoccus soli is KIS59-12T (=KACC 17340T=NBRC 113161T).

Xylophilus rhododendri sp. nov., Isolated from Flower of Royal Azalea, Rhododendron schlippenbachii.

A bacterial strain, designated CJ1-R5T, was isolated from the flower of the royal azalea plant (Rhododendron schlippenbachii) collected in Jeju Island, Republic of Korea. The strain was a Gram-negative, strictly aerobic, motile, rod-shaped bacterium, growing at a temperature range of 4-33 °C (optimum 28-30 °C), pH 5.0-9.0 (optimum pH 7.0-8.0), and 0-1% NaCl (optimum 0%). The 16S rRNA sequence analysis of strain CJ1-R5T revealed the highest sequence similarity (97.9%) with Xylophilus ampelinus ATCC 33914T, and sequence similarities of less than 97.2% with other validly named species. Phylogenetic tree analysis based on the 16S rRNA gene sequences showed that strain CJ1-R5T clustered with Xylophilus ampelinus ATCC 33914T and two uncultured bacterial clones. The only quinone observed in strain CJ1-R5T was ubiquinone-8. The polar lipids observed were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminophospholipid and two unidentified lipids. The major fatty acids were C16:0, C17:0 cyclo, and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c). The genome size of strain CJ1-R5T was 5.85 Mbp. The genomic G + C content was 68.4 mol%. ANI and dDDH values between strain CJ1-R5T and Xylophilus ampelinus ATCC 33914T were 79.0% and 22.5%, respectively. Based on the polyphasic taxonomic data, strain CJ1-R5T is considered to represent a novel species, for which the name Xylophilus rhododendri sp. nov. is proposed. The type strain is CJ1-R5T (= KACC 21265T = CCTCC AB2020030T).

Mucilaginibacter ginsengisoli sp. nov., isolated from a ginseng-cultivated soil.

A dark-pink-coloured bacterial strain, B4Y-8T, was isolated from a soil cultivated with ginseng. The 16S rRNA gene sequence of this strain showed highest similarity with Mucilaginibacter litoreus BR-18T (96.8 %), Mucilaginibacter lutimaris BR-3T (96.6 %) and Mucilaginibacter defluvii A5T (96.2 %) among the type strains of species of the genus Mucilaginibacter. Strain B4Y-8T was a strictly aerobic, Gram-stain-negative, non-motile, short-rod-shaped bacterium producing a large amount of extracellular polymeric substance. The strain grew at 10-35 °C (optimum, 25 °C), at pH 3.0-11.0 (optimum, pH 7.0) and in the presence of 0-1 % (w/v) NaCl (optimum, 0 %). The DNA G+C content of strain B4Y-8T was 49.0 mol%. It contained menaquinone 7 (MK-7) as the major isoprenoid quinone, and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) and iso-C15 : 0 as the major fatty acids. On the basis of evidence from the present polyphasic taxonomic study, strain B4Y-8T should be classified as representing a novel species of the genus Mucilaginibacter, for which the name Mucilaginibacter ginsengisoli sp. nov. is proposed. The type strain is B4Y-8T ( = KACC 18152T = JCM 30759T).

Effects of water-saving irrigation on emissions of greenhouse gases and prokaryotic communities in rice paddy soil.

The effects of water-saving irrigation on emissions of greenhouse gases and soil prokaryotic communities were investigated in an experimental rice field. The water layer was kept at 1-2 cm in the water-saving (WS) irrigation treatment and at 6 cm in the continuous flooding (CF) irrigation treatment. WS irrigation decreased CH(4) emissions by 78 % and increased N(2)O emissions by 533 %, resulting in 78 % reduction of global warming potential compared to the CF irrigation. WS irrigation did not affect the abundance or phylogenetic distribution of bacterial/archaeal 16S rRNA genes and the abundance of bacterial/archaeal 16S rRNAs. The transcript abundance of CH(4) emission-related genes generally followed CH(4) emission patterns, but the difference in abundance between mcrA transcripts and amoA/pmoA transcripts best described the differences in CH(4) emissions between the two irrigation practices. WS irrigation increased the relative abundance of 16S rRNAs and functional gene transcripts associated with Anaeromyxobacter and Methylocystis spp., suggesting that their activities might be important in emissions of the greenhouse gases. The N(2)O emission patterns were not reflected in the abundance of N(2)O emission-related genes and transcripts. We showed that the alternative irrigation practice was effective for mitigating greenhouse gas emissions from rice fields and that it did not affect the overall size and structure of the soil prokaryotic community but did affect the activity of some groups.

Actinomycetota, a central constituent microbe during long-term exposure to diazinon, an organophosphorus insecticide.

Microbial biodegradation is a primary pesticide remediation pathway. Despite diazinon is one of the most frequently used organophosphate insecticides worldwide, its effect on soil microbial community remains obscure. We hypothesize that diazinon exposure reshapes microbial community, among them increased microbes may play a crucial role in diazinon degradation. To investigate this, we collected soil from an organic farming environment, introduced diazinon, cultivated it in a greenhouse, and then assessed its effects on soil microbiomes at three distinct time points: 20, 40, and 270 days after treatment (DAT). Results from HPLC showed that the level of diazinon was gradually degraded by 98.8% at 270 DAT when compared with day zero, whereas 16S rRNA gene analysis exhibited a significant reduction in the bacterial diversity, especially at the early two time points, indicating that diazinon may exert selection pressure to the bacteria community. Here, the relative abundance of phylum Actinomycetota increased at 20 and 40 DATs. In addition, the bacterial functional gene profile employing PICRUSt2 prediction also revealed that diazinon exposure induced the genomic function related to xenobiotics biodegradation and metabolism in soil, such as CYB5B, hpaC, acrR, and ppkA. To validate if bacterial function is caused by increased relative abundance in diazinon enriched soil, further bacteria isolation resulted in obtaining 25 diazinon degradation strains out of 103 isolates. Notably, more than 70% (18 out of 25) isolates are identified as phylum Actinomycetota, which empirically confirms and correlates microbiome and PICRUSt2 results. In conclusion, this study provides comprehensive information from microbiome analysis to obtaining several bacteria isolates responsible for diazinon degradation, revealing that the phylum Actinomycetota is as a key taxon that facilitates microbial biodegradation in diazinon spoiled soil. This finding may assist in developing a strategy for microbial detoxification of diazinon, such as using an Actinomycetota rich synthetic community (SynCom).

Diversity of rhizobia associated with leguminous trees growing in South Korea.

This study was carried out to examine the diversity of 34 isolates collected from 11 species of leguminous trees growing in South Korea. Phylogenetic relationships between these 34 isolates and reference strains of the Azorhizobium, Bradyrhizobium, Mesorhizobium, Rhizobium and Ensifer/Sinorhizobium were analysed by using 16S rRNA gene sequences. Twenty-one isolates were related to Mesorhizobium, four isolates to Rhizobium, and nine isolates to Bradyrhizobium. But none of isolates were related to Sinorhizobium/Ensifer and Azorhizobium. Robinia pseudoacacia and Amorpha fruticosa were nodulated by various genotypes of rhizobia out of them, most of the isolates belonged to the genus Mesorhizobium. The isolates from Lespedeza bicolar belonged to diverse genera of Mesorhizobium, Rhizobium, and Bradyrhizobium. The isolates from Maackia amurensis and Lespedeza maximowiezii var. tomentella were phylogenetically related to the genera of Bradyrhizobium. PCR-based RAPD method and phylogenetic analysis of the 16S rRNA results revealed a high phylogenetic diversity of rhizobial strains nodulating leguminous trees in South Korea. Also, the relationships between host and bacterial phylogenies showed that only Robinia pseudoacacia, and Wisteria floribunda have significantly unique branch length than expected by chance based on phylogenetic tree.

Draft genome sequence of the biocontrol bacterium Bacillus amyloliquefaciens strain M27.

Bacillus amyloliquefaciens strain M27 is a biocontrol agent with antagonistic activities against a wide range of fungal pathogens. Here we present the 3.86-Mb draft genome sequence of the bacterium with the aims of providing insights into the genomic basis of its antifungal mechanism and facilitating its application in the biocontrol of plant diseases.

Functional robustness of a polycyclic aromatic hydrocarbon metabolic network examined in a nidA aromatic ring-hydroxylating oxygenase mutant of Mycobacterium vanbaalenii PYR-1.

In this study, we obtained over 4,000 transposon mutants of Mycobacterium vanbaalenii PYR-1 and analyzed one of the mutants, 8F7, which appeared to lose its ability to degrade pyrene while still being able to degrade fluoranthene. This mutant was identified to be defective in nidA, encoding an aromatic ring-hydroxylating oxygenase (RHO), known to be involved in the initial oxidation step of pyrene degradation. When cultured with pyrene as a sole source of polycyclic aromatic hydrocarbon (PAH), high-pressure liquid chromatography analysis revealed that the nidA mutant showed a significant decrease in the rate of pyrene degradation compared to the wild-type PYR-1, although pyrene was still being degraded. However, when incubated with PAH mixtures including pyrene, phenanthrene, and fluoranthene, the pyrene degradation rate of the mutant was higher than that of the mutant previously incubated with pyrene as a sole source of PAH. There was no significant difference between wild-type PYR-1 and the mutant in the rates of phenanthrene and fluoranthene degradation. From the whole-cell proteome analysis of mutant 8F7 induced by pyrene, we identified expression of a number of RHO enzymes which are suspected to be responsible for pyrene degradation in the nidA mutant, which had no expression of NidA. Taken together, results in this study provide direct evidence for the in vivo functional role of nidA in pyrene degradation at the level of the ring-cleavage-process (RCP) functional module but also for the robustness of the PAH metabolic network (MN) to such a genetic perturbation.

Screening of Carbofuran-Degrading Bacteria Chryseobacterium sp. BSC2-3 and Unveiling the Change in Metabolome during Carbofuran Degradation.

Carbofuran is one of the most commonly used N-methylcarbamate-based pesticides and is excellent for controlling pests; however, carbofuran also causes soil and water pollution. Although various studies have been conducted on the bioremediation of pesticide-contaminated soil, the changes occurring in the metabolome during the bioremediation of carbofuran are not fully understood. In this study, the intracellular and extracellular metabolites of the Chryseobacterium sp. BSC2-3 strain were analysed during carbofuran degradation by using a liquid chromatography-mass spectrometry-based metabolomics approach. We found that the BSC2-3 strain extracellularly transformed carbofuran into 3-hydroxycarbofuran. Intracellular metabolite analysis revealed that carbofuran mainly affected aminobenzoate degradation, ubiquinone and terpenoid-quinone biosynthesis, and arginine and proline metabolism. Carbofuran especially affected the metabolic pathway for the degradation of naphthalene and aminobenzoate. Metabolomics additionally revealed that the strain produces disease resistance inducers and plant growth regulators. We also identified the genes involved in the production of indole-3-acetic acid, which is one of the most active auxins. Overall, we identified the metabolic changes induced in carbofuran-degrading bacteria and the genes predicted to be responsible for the degradation of carbofuran.

Changes in the Composition and Microbial Community of the Pepper Rhizosphere in Field with Bacterial Wilt Disease.

Bacterial wilt caused by Ralstonia solanacearum is considered one of the most harmful diseases of pepper plants. Recently, research on plant disease control through the rhizosphere microbiome has been actively conducted. In this study, the relationship with disease occurrence between the neighboring plant confirmed by analyzing the physicochemical properties of the rhizosphere soil and changes in the microbial community. The results confirmed that the microbial community changes significantly depending on the organic matters, P2O5, and clay in the soil. Despite significant differences in microbial communities according to soil composition, Actinobacteriota at the phylum level was higher in healthy plant rhizosphere (mean of relative abundance, D: 8.05 ± 1.13; H: 10.06 ± 1.59). These results suggest that Actinobacteriota may be associated with bacterial wilt disease. In this study, we present basic information for constructing of healthy soil in the future by presenting the major microbial groups that can suppress bacterial wilt.

Biological Control Potential of Penicillium brasilianum against Fire Blight Disease.

Erwinia amylovora is a causative pathogen of fire blight disease, affecting apple, pear, and other rosaceous plants. Currently, management of fire blight relies on cultural and chemical practices, whereas it has been known that few biological resources exhibit disease control efficacy against the fire blight. In the current study, we found that an SFC20201208-M01 fungal isolate exhibits antibacterial activity against E. amylovora TS3128, and the isolate was identified as a Penicillium brasilianum based on the ß-tubulin (BenA) gene sequence. To identify active compounds from the P. brasilianum culture, the culture filtrate was partitioned with ethyl acetate and n-butanol sequentially. From the ethyl acetate layer, we identified two new compounds (compounds 3-4) and two known compounds (compounds 1-2) based on spectroscopic analyses and comparison with literature data. Of these active compounds, penicillic acid (1) exhibited promising antibacterial activity against E. amylovora TS3128 with a minimal inhibitory concentration value of 25 µg/ml. When culture filtrate and penicillic acid (125 µg/ml) were applied onto Chinese pearleaf crab apple seedlings prior to inoculation of E. amylovora TS3128, the development of fire blight disease was effectively suppressed in the treated plants. Our results provide new insight into the biocontrol potential of P. brasilianum SFC20201208-M01 with an active ingredient to control fire blight.

Biocontrol of the causal brown patch pathogen Rhizoctonia solani by Bacillus velezensis GH1-13 and development of a bacterial strain specific detection method.

Brown patch caused by the basidiomycete fungus Rhizoctonia solani is an economically important disease of cool-season turfgrasses. In order to manage the disease, different types of fungicides have been applied, but the negative impact of fungicides on the environment continues to rise. In this study, the beneficial bacteria Bacillus velezensis GH1-13 was characterized as a potential biocontrol agent to manage brown patch disease. The strain GH1-13 strongly inhibited the mycelial growth of turf pathogens including different anastomosis groups of R. solani causing brown patch and large patch. R. solani AG2-2(IIIB) hyphae were morphologically changed, and fungal cell death resulted from exposure to the strain GH1-13. In addition, the compatibility of fungicides with the bacterial strain, and the combined application of fungicide azoxystrobin and the strain in brown patch control on creeping bentgrass indicated that the strain could serve as a biocontrol agent. To develop strain-specific detection method, two unique genes from chromosome and plasmid of GH1-13 were found using pan-genome analysis of 364 Bacillus strains. The unique gene from chromosome was successfully detected using both SYBR Green and TaqMan qPCR methods in bacterial DNA or soil DNA samples. This study suggests that application of GH1-13 offers an environmentally friendly approach via reducing fungicide application rates. Furthermore, the developed pipeline of strain-specific detection method could be a useful tool for detecting and studying the dynamics of specific biocontrol agents.

Zobellella aerophila sp. nov., isolated from seashore sand, and emended description of the genus Zobellella.

A strictly aerobic, nitrate-reducing, motile, rod-shaped member of the class Gammaproteobacteria, designated strain JC2671(T), was isolated from a seashore sand sample from Dokdo, Korea. The isolate reduced nitrate to nitrite, but not to nitrogen, and required NaCl for growth. 16S rRNA gene sequence analysis indicated that the isolate belonged to the genus Zobellella within the order Alteromonadales with sequence similarities of 96.0-97.6 % to strains of Zobellella species with validly published names. However, in DNA-DNA hybridization studies, a low genomic relatedness (43 %) between strain JC2671(T) and the type strain of Zobellella denitrificans indicated that the isolate represented a novel genomic species. The polar lipid pattern (phosphatidylethanolamine and phosphatidylglycerol), predominant cellular fatty acids [C(16 : 0), summed feature 3 (C(16 : 1)ω6c and/or C(16 : 1)ω7c) and summed feature 8 (C(18 : 1)ω6c and/or C(18 : 1)ω7c)] and the DNA G+C content (59 mol%) of the novel strain were consistent with its assignment to the genus Zobellella. In contrast, a number of phenotypic characteristics, namely a requirement of NaCl for growth, the inability to grow under facultatively anaerobic conditions, the absence of nitrite reduction and differences in carbohydrate utilization and enzymic activities, clearly distinguished the novel isolate from other species of the genus Zobellella. Data from this polyphasic study indicate that strain JC2671(T) represents a novel species in the genus Zobellella, for which the name Zobellella aerophila sp. nov. is proposed. The type strain is JC2671(T) ( = KACC 15081(T)  = JCM 17110(T)). The description of the genus Zobellella has been emended accordingly.

Effect of Bacillus mesonae H20-5 Treatment on Rhizospheric Bacterial Community of Tomato Plants under Salinity Stress.

Plant growth-promoting bacteria improve plant growth under abiotic stress conditions. However, their effects on microbial succession in the rhizosphere are poorly understood. In this study, the inoculants of Bacillus mesonae strain H20-5 were administered to tomato plants grown in soils with different salinity levels (EC of 2, 4, and 6 dS/m). The bacterial communities in the bulk and rhizosphere soils were examined 14 days after H20-5 treatment using Illumina MiSeq sequencing of the bacterial 16S rRNA gene. Although the abundance of H20-5 rapidly decreased in the bulk and rhizosphere soils, a shift in the bacterial community was observed following H20-5 treatment. The variation in bacterial communities due to H20-5 treatment was higher in the rhizosphere than in the bulk soils. Additionally, the bacterial species richness and diversity were greater in the H20-5 treated rhizosphere than in the control. The composition and structure of the bacterial communities varied with soil salinity levels, and those in the H20-5 treated rhizosphere soil were clustered. The members of Actinobacteria genera, including Kineosporia, Virgisporangium, Actinoplanes, Gaiella, Blastococcus, and Solirubrobacter, were enriched in the H20-5 treated rhizosphere soils. The microbial co-occurrence network of the bacterial community in the H20-5 treated rhizosphere soils had more modules and keystone taxa compared to the control. These findings revealed that the strain H20-5 induced systemic tolerance in tomato plants and influenced the diversity, composition, structure, and network of bacterial communities. The bacterial community in the H20-5 treated rhizosphere soils also appeared to be relatively stable to soil salinity changes.

A native conjugative plasmid confers potential selective advantages to plant growth-promoting Bacillus velezensis strain GH1-13.

The conjugative plasmid (pBV71) possibly confers a selective advantage to Bacillus velezensis strain GH1-13, although a selective marker gene is yet to be identified. Here we show that few non-mucoid wild-type GH1-13 cells are spontaneously converted to mucoid variants with or without the loss of pBV71. Mucoid phenotypes, which contain or lack the plasmid, become sensitive to bacitracin, gramicidin, selenite, and tellurite. Using the differences in antibiotic resistance and phenotype, we isolated a reverse complement (COM) and a transconjugant of strain FZB42 with the native pBV71. Transformed COM and FZB42p cells were similar to the wild-type strain GH1-13 with high antibiotic resistance and slow growth rates on lactose compared to those of mucoid phenotypes. RT-PCR analysis revealed that the expression of plasmid-encoded orphan aspartate phosphatase (pRapD) was coordinated with a new quorum-sensing (QS) cassette of RapF2-PhrF2 present in the chromosome of strain GH1-13, but not in strain FZB42. Multi-omics analysis on wild-type and plasmid-cured cells of strain GH1-13 suggested that the conjugative plasmid expression has a crucial role in induction of early envelope stress response that promotes cell morphogenesis, biofilm formation, catabolite repression, and biosynthesis of extracellular-matrix components and antibiotics for protection of host cell during exponential phase.

Dispute cases related to pain management in Korea: analysis of Korea Medical Dispute Mediation and Arbitration Agency data.

BACKGROUND: Various developments in imaging techniques, interventional procedures, and medications for pain management have beneficial consequences. However, the nature of pain management often results in physicians becoming involved in medico-legal disputes with patients who purposely or accidentally bring litigation. METHODS: Data on medical disputes cases related to pain management were collected and analyzed through the Korea Medical Dispute Mediation and Arbitration Agency from 2012 to 2016. RESULTS: In total, we identified 210 public-disclosed cases; of these, we identified 36 cases related to pain management. The department of orthopedics (n = 9, 25%) was the most related to these pain management cases. Pain management was most commonly offered for pain in the lumbar region (n = 13, 37%), lower extremities (n = 12, 34%), and for infection (n = 7, 19%). The time spent resolving disputes ranged from 8.0 to 17.5 months and the final settlement amount ranged from 1,800,000 to 15,000,000 Korean won. Causal relationships and medical malpractice were the most common controversial subjects of legal debate. CONCLUSIONS: Various characteristics of medical disputes related to pain management in Korea were identified. Information regarding medical disputes in pain management should be available to help prevent further disputes and litigation, which is also useful to both patients and pain physicians. Guidelines and recommendations for pain management are needed, especially those focused on medico-legal cases.

Paenibacillus lycopersici sp. nov. and Paenibacillus rhizovicinus sp. nov., isolated from the rhizosphere of tomato (Solanum lycopersicum).

Two Gram-stain-positive, rod-shaped, endospore-forming bacteria, designated 12200R-189T and 14171R-81T were isolated from the rhizosphere of tomato plants. The 16S rRNA gene sequence similarity between strains 12200R-189T and 14171R-81T were 97.2%. Both strains showed the highest 16S rRNA gene sequence similarities to Paenibacillus sacheonensis SY01T (96.3% and 98.0%, respectively). The genome of strain 12200R-189T was approximately 6.7 Mb in size with 5,750 protein-coding genes (CDSs) and the G + C content was 58.1 mol%, whereas that of strain 14171R-81T comprised one chromosome of 7.0 Mb and two plasmids (0.2 Mb each) with 6,595 CDSs and the G + C content was 54.5 mol%. Comparative genome analysis revealed that average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values among 12200R-189T, 14171R-81T, and other closely related species were below the cut-off levels 95% and 70%, respectively. Strain 12200R-189T grew at a temperature range of 15-40°C, pH 6.0-9.0, and 0-3% NaCl (w/v), whereas strain 14171R-81T grew at a temperature range of 10-37°C, pH 6.0-8.0, and 0-1% NaCl (w/v). Menaquinone-7 (MK-7) was the only isoprenoid quinone detected in both strains. The predominant cellular fatty acids (> 10%) were iso-C15:0, anteiso-C15:0, and iso-C16:0. The polar lipids of strain 12200R-189T were diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), aminophospholipid (APL), phospholipid (PL), phosphatidylglycolipid (PGL), and four aminophosphoglycolipids (APGLs) and those of strain 14171R-81T were DPG, PG, PE, APL, three PLs, two PGLs, and three APGLs. Based on phylogenetic, genomic, phenotypic, and chemotaxonomic analyses, strains 12200R-189T and 14171R-81T represent two novel species of the genus Paenibacillus, for which the names Paenibacillus lycopersici sp. nov. and Paenibacillus rhizovicinus sp. nov. are proposed. The type strains are 12200R-189T (= KACC 19916T = CCTCC AB 2020027T) and 14171R-81T (= KACC 19915T = CCTCC AB 2020026T).

Different types of agricultural land use drive distinct soil bacterial communities.

Biogeographic patterns in soil bacterial communities and their responses to environmental variables are well established, yet little is known about how different types of agricultural land use affect bacterial communities at large spatial scales. We report the variation in bacterial community structures in greenhouse, orchard, paddy, and upland soils collected from 853 sites across the Republic of Korea using 16S rRNA gene pyrosequencing analysis. Bacterial diversities and community structures were significantly differentiated by agricultural land-use types. Paddy soils, which are intentionally flooded for several months during rice cultivation, had the highest bacterial richness and diversity, with low community variation. Soil chemical properties were dependent on agricultural management practices and correlated with variation in bacterial communities in different types of agricultural land use, while the effects of spatial components were little. Firmicutes, Chloroflexi, and Acidobacteria were enriched in greenhouse, paddy, and orchard soils, respectively. Members of these bacterial phyla are indicator taxa that are relatively abundant in specific agricultural land-use types. A relatively large number of taxa were associated with the microbial network of paddy soils with multiple modules, while the microbial network of orchard and upland soils had fewer taxa with close mutual interactions. These results suggest that anthropogenic agricultural management can create soil disturbances that determine bacterial community structures, specific bacterial taxa, and their relationships with soil chemical parameters. These quantitative changes can be used as potential biological indicators for monitoring the impact of agricultural management on the soil environment.

Plant growth-promoting activity of beta-propeller protein YxaL secreted from Bacillus velezensis strain GH1-13.

YxaL is conserved within the Bacillus subtilis species complex associated with plants and soil. The mature YxaL protein contains a repeated beta-propeller domain, but the subcellular location and function of YxaL has not been determined. The gene encoding the mature YxaL protein was PCR amplified from genomic DNA of B. velezensis strain GH1-13 and used for recombinant protein production. A rabbit polyclonal antibody against the purified YxaL was generated and used for western blotting to determine the constitutive expression and secretion of YxaL. During normal culture growth of strain GH1-13, levels of the constitutively secreted YxaL were slowly rising to 100 µg L-1, and degraded with a half-life of 1.6 h in the culture medium. When the effects of YxaL on plant seed germination and seedling growth were examined, it was shown that seed treatment of Arabidopsis thaliana and rice (Oryza sativa L.) with purified YxaL at the optimal concentration of 1 mg L-1 was effective at improving the root growth of plants. Seedlings from the treated Arabidopsis seeds markedly increased transcription of a 1-aminocyclopropane-1-carboxylate synthetase marker gene (ACS11) but reduced expression of auxin- and abscisic acid-responsive marker genes (IAA1, GH3.3, and ABF4), especially when provided with exogenous auxin. Horticulture experiments showed that pepper (Capsicum annuum) seeds treated with 1 mg L-1 YxaL in a soaking solution increased shoot growth and improved tolerance to drought stress. We hypothesize that YxaL secreted from plant growth-promoting Bacillus cells has a significant impact on plant roots, with the potential to improve plant growth and stress tolerance.