Flavobacterium sp. strain GJW24 ameliorates drought resistance in Arabidopsis and Brassica.

Candidate strains that contribute to drought resistance in plants have been previously screened using approximately 500 plant growth-promoting rhizobacteria (PGPR) obtained from Gotjawal, South Korea, to further understand PGPR associated with plant drought tolerance. In this study, a selected PGPR candidate, Flavobacterium sp. strain GJW24, was employed to enhance plant drought tolerance. GJW24 application to Arabidopsis increased its survival rate under drought stress and enhanced stomatal closure. Furthermore, GJW24 promoted Arabidopsis survival under salt stress, which is highly associated with drought stress. GJW24 ameliorated the drought/salt tolerance of Brassica as well as Arabidopsis, indicating that the drought-resistance characteristics of GJW24 could be applied to various plant species. Transcriptome sequencing revealed that GJW24 upregulated a large portion of drought- and drought-related stress-inducible genes in Arabidopsis. Moreover, Gene Ontology analysis revealed that GJW24-upregulated genes were highly related to the categories involved in root system architecture and development, which are connected to amelioration of plant drought resistance. The hyper-induction of many drought/salt-responsive genes by GJW24 in Arabidopsis and Brassica demonstrated that the drought/salt stress tolerance conferred by GJW24 might be achieved, at least in part, through regulating the expression of the corresponding genes. This study suggests that GJW24 can be utilized as a microbial agent to offset the detrimental effects of drought stress in plants.

Pullusurfactins A‒C, new biosurfactants produced by Aureobasidium pullulans A11231-1-58 from Chrysanthemum boreale Makino.

Biosurfactants have found widespread use across multiple industrial fields, including medicine, food, cosmetics, detergents, pulp, and paper, as well as the degradation of oil and fat. The culture broth of Aureobasidium pullulans A11231-1-58 isolated from flowers of Chrysanthemum boreale Makino exhibited potent surfactant activity. Surfactant activity-guided fractionation led to the isolation of three new biosurfactants, pullusurfactins A‒C (1‒3). Their chemical structures were established through the use of spectroscopic techniques, predominantly 1D and 2D NMR, in conjunction with mass measurements. We evaluated the surface tension activities of isolated compounds. At 1.0 mg l-1, these compounds showed high degrees of surfactant activity (31.15 dyne/cm, 33.75 dyne/cm, and 33.83 dyne/cm, respectively).

Production of a New Biosurfactant by a New Yeast Species Isolated from Prunus mume Sieb. et Zucc.

Biosurfactants reduce surface and interfacial tension due to their amphiphilic properties and are an eco-friendly alternative for chemical surfactants. In this study, a new yeast strain JAF-11 that produces a biosurfactant was selected using drop collapse method, and the properties of the extracts were investigated. The nucleotide sequences of the strain were compared with closely related strains and identified based on the D1/D2 domain of the large subunit ribosomal DNA (LSU) and internal transcribed spacer (ITS) regions. Neodothiora populina CPC 39399T, the closest species with strain JAF-11, showed a sequence similarity of 97.75% for LSU and 94.27% for ITS, respectively. The result suggests that the strain JAF-11 represents a distinct species that cannot be assigned to any existing genus or species in the family Dothideaceae. Strain JAF-11 produced a biosurfactant reducing the surface tension of water from 72 mN/m to 34.5 mN/m on the sixth day of culture and the result of measuring the critical micelle concentration (CMC) by extracting the crude biosurfactant was found to be 24 mg/l. The molecular weight 502 of the purified biosurfactant was confirmed by measuring the fast atom bombardment mass spectrum. The chemical structure was analyzed by measuring 1H nuclear magnetic resonance (NMR), 13C NMR, and two-dimensional NMRs of the compound. The molecular formula was C26H46O9, and it was composed of one octanoyl group and two hexanoyl groups to myo-inositol moiety. The new biosurfactant is the first report of a compound produced by a new yeast strain, JAF-11.

Two Novel Biosurfactants Produced by Aureobasidium pullulans A11211-4-57 from a Fleabane, Erigeron annus (L.) pers.

Biosurfactants have been widely used in various industrial fields including medicine, food, cosmetics, detergent, pulp and paper, and oil and fat degradation. The culture broth of Aureobasidium pullulans A11211-4-57 using glucose as carbon source exhibited potent surfactant activity. The culture broth was separated by column chromatographies using ODS, silica gel, and Sephadex LH-20 resins, consecutively, to provide two biosurfactants. Based on mass and NMR measurements, their structures were determined as myo-inositol lipids and named pullusurfactans F and G. These compounds showed a high degree of activity, with 27.25 mN/m and 24.07 mN/m, respectively, at 1.0 mg l-1, which is useful for washing and cleaning agents.

Bacillus subtilis strain GOT9 confers enhanced tolerance to drought and salt stresses in Arabidopsis thaliana and Brassica campestris.

Soil is a primary source of water and inorganic nutrients vital for plant growth. In particular, the rhizosphere, a microecological region around the plant roots, is enriched with root exudates that enable beneficial microbial communities to form. Plant growth-promoting rhizobacteria (PGPR) are rhizosphere bacteria that contribute to the improvement of plant growth through diverse physiological mechanisms. Identifying PGPR is beneficial for agriculture because their use can effectively increase the productivity of plants without the harmful side effects of chemical fertilizers. To further enrich the pool of PGPR that contribute to abiotic stress resistance in plants, we screened roughly 491 bacteria that had previously been isolated in soil from Gotjawal in Jeju island, South Korea. Among several candidates, the application of Bacillus subtilis strain GOT9, led to the enhancement of drought and salt stress tolerance in Arabidopsis. In agreement with the increased stress tolerance phenotypes, its application resulted in increases in the transcripts of various drought stress- and salt stress-inducible genes in the absence or presence of the stresses. Furthermore, the treatment resulted in improved lateral root growth and development in Arabidopsis. GOT9 also led to enhanced tolerance against drought and salt stresses and to upregulation of drought-inducible genes in Brassica, a closely related crop to Arabidopsis. Taken together, these results show that GOT9 could be utilized as a biotic resource that effectively minimizes damage to plants from environmental stresses.

Characterization of a nifH-Harboring Bacterial Community in the Soil-Limited Gotjawal Forest.

Using a high-throughput metagenomic approach, we evaluated nifH-harboring bacterial communities and their assembly in the Gotjawal forest, which was naturally formed on basalt rocks with thin layer of soil. Significant differences in soil properties and community structure were observed in comparison with similar communities in various habitats, including other lava-formed forests (on Jeju Island and in Hawaii) and in regions with high humidity (Florida) or low temperatures (Alaska). nifH-harboring bacterial communities were found to assemble along gradients of environmental factors, particularly cation-exchange capacity. Unlike in other regions, in the Gotjawal forest, Paenibacillus and Clostridium, which belong to the phylum Firmicutes, were present in significantly higher proportion than in other regions. Network analysis suggested that much fewer co-occurrence relationships occurred in the Gotjawal forest than in other lava-formed forests. Our results indicate that the unique nifH-harboring bacterial community and its assembly in the Gotjawal forest are due to its distinctive soil properties, which has implications for microbial interactions and functional potentials.

Correction: Microbial community structure and functional potential of lava-formed Gotjawal soils in Jeju, Korea.

[This corrects the article DOI: 10.1371/journal.pone.0204761.].

Microbial community structure and functional potential of lava-formed Gotjawal soils in Jeju, Korea.

The Gotjawal areas of Jeju Island, Korea, are comprised of unmanaged forests growing on volcanic soils. They support unique assemblages of vascular plants from both northern and southern hemispheres, but are threatened by human disturbance. The health and ecosystem function of these assemblages likely depends in part on the diversity and community structure of soil microbial communities, about which little is known. To assess the diversity of Gotjawal soil microbial communities, twenty samples were collected in November 2010 from 4 representatives of Gotjawal forests. While soil properties and microbial communities measured by 16S rRNA gene sequence data were marginally distinct among sites by PERMANOVA (p = 0.017-0.191), GeoChip data showed significant differences among sites (p <0.006). Gene composition overall, and the composition of 3 functional gene categories had similar structures themselves and similar associations with environmental factors. Among these communities, phosphorous cycling genes exhibited the most distinct patterns. 16S rRNA gene sequence data resulted in a mean 777 operational taxonomic units (OTUs), which included the following major phyla: Proteobacteria (27.9%), Actinobacteria (17.7%), Verrucomicrobia (14.3%), Acidobacteria (9.6%), Planctomycetes (9.8%), Bacteroidetes (8.9%), and Chloroflexi (2.2%). Indicator species analysis (ISA) was used to determine the taxa with high indicator value, which represented the following: uncultured Chlamydiaceae, Caulobacter, uncultured Sinobacteraceae, Paenibacillus, Arenimonas, Clostridium sensu.stricto, uncultured Burkholderiales incertae sedis, and Nocardioides in Aewol (AW), Aquicella, uncultured Planctomycetia, and Aciditerrimonas in Gujwa-Seongsan (GS), uncultured Acidobacteria Gp1, and Hamadaea in Hankyeong-Andeok (HA), and Bosea, Haliea, and Telmatocola in Jocheon-Hamdeok (JH) Gotjawal. Collectively, these results demonstrated the uniqueness of microbial communities within each Gotjawal region, likely reflecting different patterns of soil, plant assemblages and microclimates.

Pullusurfactans A-E, new biosurfactants produced by Aureobasidium pullulans A11211-4-57 from a fleabane, Erigeron annus (L.) pers.

Yeast biosurfactants have potent applications in medical, cosmeceutical, and food industries due to their specific modes of action, low toxicity, and applicability. In this study, biosurfactant-producing yeasts were screened for various industrial applications. Among them, Aureobasidium pullulans strain A11211-4-57 with potent surfactant activity from fleabane flower, Erigeron annus (L.) pers., was selected. From culture supernatant of strain A11211-4-57, five new low-surface-tension chemicals designated as pullusurfactans A-E were identified through consecutive chromatography steps, involving ODS, silica gel, Sephadex LH-20, and ODS Sep-pak cartridge columns. Based on mass and NMR measurements, structures of pullusurfactans A-E were determined as myo-inositol lipids with molecular formulae of C20H35O9, C18H32O8, C20H35O9, C24H42O9, and C18H32O8, respectively. These compounds exhibited potent biosurfactant activities (22.90, 22.40, 32.28, 25.28, and 22.44 mN/m, respectively). These results suggest that these novel biosurfactants have potential use as biosurfactants in industrial aspect.

Jatrophihabitans telluris sp. nov., isolated from sediment soil of lava forest wetlands and the emended description of the genus Jatrophihabitans.

A novel actinobacterial strain, designated N237T, was isolated from sediment soil of wetlands at Meonmulkkak, Dongbaek-Dongsan, the lava forest, Gotjawal, Jeju, Republic of Korea. Cells of strain N237T were Gram-stain-positive, non-motile rods and formed pale yellow colonies on ten-fold diluted Reasoner's 2A agar. Strain N237T contained iso-C16 : 0 and C17 : 1ω8c as the major fatty acids, MK-9(H4) as the predominant isoprenoid quinone and meso-DAP as the diamino acid in the peptidoglycan. It contained diphosphatidylglycerol, phosphatidylinositol polymannosides, an unidentified phospholipid, an unidentified aminophospholipid, an unidentified aminolipid, two unidentified glycophospholipids, three unidentified glycolipids and two unidentified lipids as polar lipids. The DNA G+C content was 68.1 mol%. Strain N237T formed a separate lineage in the genus Jatrophihabitans, as demonstrated by phylogenetic analysis based on 16S rRNA sequencing. It was most closely related to Jatrophihabitans soli KIS75-12T (95.6 % sequence similarity). The combined phenotypic, chemotaxonomic and phylogenetic characteristics supported the conclusion that strain N237T represents a novel species in the genus Jatrophihabitans, for which the name Jatrophihabitans telluris sp. nov. is proposed. The type strain is N237T (=KCTC 39922T=NRRL B-65477T).

Mucilaginibacter craterilacus sp. nov., isolated from sediment soil of a crater lake.

A novel bacterial strain, designated N60AT, was isolated from sediment soil of crater lake, Baekrokdam, Hallasan, Jeju, Republic of Korea. Cells of N60AT were Gram-reaction-negative, oxidase- and catalase-positive, non-motile rods and formed transparent white colonies on ten-fold diluted R2A agar. N60AT contained summed feature 3 (C16 : 1ω7c/C16 : 1ω6c), iso-C15 : 0 and iso-C17 : 0 3-OH as the major fatty acids and MK-7 as the predominant isoprenoid quinone. It contained phosphatidylethanolamine as the predominant polar lipid. The DNA G+C content was 44.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing revealed that N60AT formed a separate lineage in the genus Mucilaginibacter and that it was most closely related to Mucilaginibacter frigoritolerans FT22T (96.5 % sequence similarity). Phenotypic, chemotaxonomic and phylogenetic characteristics supported the conclusion that N60AT represents a novel species of the genus Mucilaginibacter, for which the name Mucilaginibacter craterilacus sp. nov. is proposed. The type strain is N60AT (=KCTC 52404T=NRRL B-65396T).

Sphingomonas gotjawalisoli sp. nov., isolated from soil of a lava forest.

A bacterial strain, designated SN6-9T, was isolated from soil of the Gotjawal, lava forest, located in Jeju, Republic of Korea. Strain SN6-9T was Gram-stain-negative, motile, oxidase- and catalase-negative, yellow-pigmented and rod-shaped. It contained summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) as the major fatty acids, Q-10 as the predominant isoprenoid quinone, sym-homospermidine as the major polyamine and diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingoglycolipid and two unidentified phospholipids as the polar lipids. The DNA G+C content was 64.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain formed a separate lineage in the genus Sphingomonas. Based on the results from this polyphasic taxonomic study, it is concluded that strain SN6-9T represents a novel species in the genus Sphingomonas. The name Sphingomonas gotjawalisoli sp. nov. is proposed; the type strain is SN6-9T (=KCTC 52405T=NRRL B-65395T).

Nocardioides baekrokdamisoli sp. nov., isolated from soil of a crater lake.

A novel actinobacterial strain, B2-12T, was isolated from soil of a crater lake, Baekrokdam, Hallasan, Jeju, Republic of Korea. Cells of strain B2-12T were Gram-stain-positive, non-motile, non-spore-forming and coccoid to short-rod-shaped. Phylogenetic analysis, based on 16S rRNA gene sequencing, showed that strain B2-12T belonged to the genus Nocardioides and shared highest sequence similarity with 'Nocardioidespaucivorans' KIS31-44 (98.4 %). The predominant isoprenoid quinone was MK-8(H4). The major fatty acids of strain B2-12T were C16 : 1 (ω7c and/or ω6c), summed feature 9 (iso-C17 : 1ω9c and/or C16 : 0 10-methyl), C17 : 0 10-methyl, iso-C16 : 0, C16 : 0 and C17 : 1ω6c. The diagnostic diamino acid in the cell-wall peptidoglycan was ll-diaminopimelic acid. It contained diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol as the polar lipids. The DNA G+C content was 67.0 mol%. Based on phylogenetic, chemotaxonomic and phenotypic data, 16S rRNA gene sequence comparisons and DNA-DNA hybridization data, strain B2-12T represents a novel species in the genus Nocardioides, for which the name Nocardioidesbaekrokdamisolisp. nov. is proposed. The type strain is B2-12T (=KCTC 39748T=NRRL B-65313T=DSM 100725T).

Paenibacillus baekrokdamisoli sp. nov., isolated from soil of crater lake.

A novel bacterial strain, Back-11T, was isolated from sediment soil of a crater lake, Baekrokdam, Hallasan, Jeju, Republic of Korea. Cells of strain Back-11T were Gram-stain-positive, motile, endospore-forming, rod-shaped and oxidase- and catalase-positive. It contained anteiso-C15 : 0 as the major fatty acid, menaquinone-7 (MK-7) as the predominant isoprenoid quinone, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and four unidentified aminophospholipids as the main polar lipids, and meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan. The DNA G+C content was 45.3 mol%. Phylogenetic analysis, based on 16S rRNA gene sequencing, showed that strain Back-11T was most closely related to Paenibacillus taihuensis THMBG22T (95.5 % similarity) and fell into a clade in the genus Paenibacillus. On the basis of phylogenetic, chemotaxonomic and phenotypic data, strain Back-11T represents a novel species in the genus Paenibacillus, for which the name Paenibacillus baekrokdamisoli sp. nov. is proposed. The type strain is Back-11T ( = KCTC 33723T = CECT 8890T).

Sphingomonas vulcanisoli sp. nov., isolated from soil of a lava forest.

A Gram-stain-negative, non-motile, yellow-pigmented and rod-shaped bacterial strain, designated SN6-13T, was isolated from soil of the Gotjawal, lava forest, located in Jeju, Republic of Korea. Cells of strain SN6-13T were oxidase- and catalase-positive. The isolate contained Q-10 as the predominant isoprenoid quinone, summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C16 : 0 as the major fatty acids, sym-homospermidine as the major polyamine and diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingoglycolipid, ninhydrinphosphatidylglycerol and two unidentified aminophospholipids as the polar lipids. The DNA G+C content was 64.6 mol%. In phylogenetic analyses based on 16S rRNA gene sequencing, strain SN6-13T was most closely related to Sphingomonas laterariae LNB2T (95.4 % sequence similarity) and formed a separate lineage in the genus Sphingomonas. Based on phenotypic, chemotaxonomic and phylogenetic characteristics, it is concluded that strain SN6-13T represents a novel species of the genus Sphingomonas, for which the name Sphingomonas vulcanisoli sp. nov. is proposed. The type strain is SN6-13T ( = KCTC 42454T = CECT 8804T).

Cohnella collisoli sp. nov., isolated from lava forest soil.

A novel bacterial strain, NKM-5(T), was isolated from soil of a lava forest in Nokkome Oreum, Jeju, Republic of Korea. Cells of strain NKM-5(T) were Gram-stain-positive, motile, endospore-forming, rod-shaped and oxidase- and catalase-positive. Strain NKM-5(T) contained anteiso-C15 : 0 and iso-C16 : 0 as the major fatty acids; menaquinone-7 (MK-7) as the predominant isoprenoid quinone; diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, lysyl-phosphatidylglycerol, an unidentified phospholipid and three unidentified aminophospholipids as the polar lipids; and meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan. The DNA G+C content was 48.3 mol%. Phylogenetic analysis, based on 16S rRNA gene sequencing, showed that strain NKM-5(T) was most closely related to Cohnella lupini RLAHU4B(T) (96.9% sequence similarity) and fell into a clade in the genus Cohnella. On the basis of phylogenetic, chemotaxonomic and phenotypic data, strain NKM-5(T) represents a novel species of the genus Cohnella, for which the name Cohnella collisoli sp. nov. is proposed. The type strain is NKM-5(T) ( = KCTC 33634(T) = CECT 8805(T)).

Artemisia asiatica Nakai Attenuates the Expression of Proinflammatory Mediators in Stimulated Macrophages Through Modulation of Nuclear Factor-κB and Mitogen-Activated Protein Kinase Pathways.

The present study aimed to examine the anti-inflammatory effects and potential mechanism of action of Artemisia asiatica Nakai (A. asiatica Nakai) extract in activated murine macrophages. A. asiatica Nakai extract showed dose-dependent suppression of lipopolysaccharide (LPS)-induced nitric oxide, inducible nitric oxide synthase, and cyclooxygenase-2 activity. It also showed dose-dependent inhibition of nuclear factor-κB (NF-κB) translocation from the cytosol to the nucleus and as an inhibitor of NF-κB-alpha phosphorylation. The extract's inhibitory effects were found to be mediated through NF-κB inhibition and phosphorylation of extracellular signal-regulated kinase 1/2 and p38 in LPS-stimulated J774A.1 murine macrophages, suggesting a potential mechanism for the anti-inflammatory activity of A. asiatica Nakai. To our knowledge, this is the first report of the anti-inflammatory effects of A. asiatica Nakai on J774A.1 murine macrophages; these results may help develop functional foods possessing an anti-inflammatory activity.

A novel biosurfactant produced by Aureobasidium pullulans L3-GPY from a tiger lily wild flower, Lilium lancifolium Thunb.

Yeast biosurfactants are important biotechnological products in the food industry, and they have medical and cosmeceutical applications owing to their specific modes of action, low toxicity, and applicability. Thus, we have isolated and examined biosurfactant-producing yeast for various industrial and medical applications. A rapid and simple method was developed to screen biosurfactant-producing yeasts for high production of eco-friendly biosurfactants. Using this method, several potential niches of biosurfactant-producing yeasts, such as wild flowers, were investigated. We successfully selected a yeast strain, L3-GPY, with potent surfactant activity from a tiger lily, Lilium lancifolium Thunb. Here, we report the first identification of strain L3-GPY as the black yeast Aureobasidium pullulans. In addition, we isolated a new low-surface-tension chemical, designated glycerol-liamocin, from the culture supernatant of strain L3-GPY through consecutive chromatography steps, involving an ODS column, solvent partition, silica gel, Sephadex LH-20, and an ODS Sep-Pak cartridge column. The chemical structure of glycerol-liamocin, determined by mass spectrometry and nuclear magnetic resonance spectroscopy, indicates that it is a novel compound with the molecular formula C33H62O12. Furthermore, glycerol-liamocin exhibited potent biosurfactant activity (31 mN/m). These results suggest that glycerol-liamocin is a potential novel biosurfactantfor use in various industrial applications.

Complete Genome Sequence of Halophilic Yeast Meyerozyma caribbica MG20W Isolated from Rhizosphere Soil.

Meyerozyma caribbica MG20W was originally isolated from rhizosphere soil on reclaimed land in the Republic of Korea. We describe herein the 10.64-Mbp-long genome sequence of M. caribbica MG20W, which exhibits high salt resistance.