Rhizosphere microbial ecological characteristics of strawberry root rot.

Introduction: Strawberry (Fragaria × ananassa Duch.) holds a preeminent position among small fruits globally due to its delectable fruits and significant economic value. However, strawberry cultivation is hampered by various plant diseases, hindering the sustainable development of the strawberry industry. The occurrence of plant diseases is closely linked to imbalance in rhizosphere microbial community structure. Methods: In the present study, a systematic analysis of the differences and correlations among non-culturable microorganisms, cultivable microbial communities, and soil nutrients in rhizosphere soil, root surface soil, and non-rhizosphere soil of healthy and diseased strawberry plants affected by root rot was conducted. The goal was to explore the relationship between strawberry root rot occurrence and rhizosphere microbial community structure. Results: According to the results, strawberry root rot altered microbial community diversity, influenced fungal community composition in strawberry roots, reduced microbial interaction network stability, and enriched more endophytic-phytopathogenic bacteria and saprophytic bacteria. In addition, the number of bacteria isolated from the root surface soil of diseased plants was significantly higher than that of healthy plants. Discussion: In summary, the diseased strawberry plants changed microbial community diversity, fungal species composition, and enriched functional microorganisms significantly, in addition to reshaping the microbial co-occurrence network. The results provide a theoretical basis for revealing the microecological mechanism of strawberry root rot and the ecological prevention and control of strawberry root rot from a microbial ecology perspective.

Plant resistance to tomato yellow leaf curl virus is enhanced by Bacillus amyloliquefaciens Ba13 through modulation of RNA interference.

Introduction: Tomato yellow leaf curl virus (TYLCV), which is a typical member of the genus Begomovirus, causes severe crop yield losses worldwide. RNA interference (RNAi) is an important antiviral defense mechanism in plants, but whether plant beneficial microbes used as biocontrol agents would modulate RNAi in defense against TYLCV remains unclear. Methods: Here, we employed whole-transcriptome, bisulfite, and small RNA sequencing to decipher the possible role of Bacillus amyloliquefaciens Ba13 as a bacterial biocontrol agent against TYLCV in RNAi modulation. Results: Potted tomato plants were exposed to whiteflies for natural viral infection 14 days after bacterial inoculation. Compared with non-inoculated controls, the abundance of TYLCV gene in the leaves of inoculated plants decreased by 70.1% at 28 days post-infection, which mirrored the pattern observed for plant disease index. The expression of the ARGONAUTE family genes (e.g., AGO3, AGO4, AGO5, and AGO7) involved in antiviral defense markedly increased by 2.44-6.73-fold following bacterial inoculation. The methylation level at CpG site 228 (in the open reading frame region of the RNA interference suppressing gene AV2) and site 461 (in the open reading frame regions of AV1 and AV2) was 183.1 and 63.0% higher in inoculated plants than in non-inoculated controls, respectively. The abundances of 10 small interfering RNAs matched to the TYLCV genome were all reduced in inoculated plants, accompanied by enhancement of photosystem and auxin response pathways. Discussion: The results indicate that the application of Ba. amyloliquefaciens Ba13 enhances plant resistance to TYLCV through RNAi modulation by upregulating RNAi-related gene expression and enhancing viral genome methylation.

Widely targeted metabolomic, transcriptomic, and metagenomic profiling reveal microbe-plant-metabolic reprogramming patterns mediated by Streptomyces pactum Act12 enhance the fruit quality of Capsicum annuum L.

Plant growth-promoting rhizobacteria, such as Streptomyces pactum Act12, promote crop growth and stress resistance, but their contribution to fruit quality is still poorly understood. Herein we conducted a field experiment to ascertain the effects of S. pactum Act12-mediated metabolic reprogramming and underlying mechanisms in pepper (Capsicum annuum L.) fruit based on widely targeted metabolomic and transcriptomic profiling. We additionally performed metagenomic analysis to elucidate the potential relationship between S. pactum Act12-mediated reshaping of rhizosphere microbial communities and pepper fruit quality. Soil inoculation with S. pactum Act12 considerably increased the accumulation of capsaicinoids, carbohydrates, organic acids, flavonoids, anthraquinones, unsaturated fatty acids, vitamins, and phenolic acids in pepper fruit samples. Consequently, fruit flavor, taste, and color were modified, accompanied by elevated contents of nutrients and bioactive compounds. Increased microbial diversity and recruitment of potentially beneficial taxa were observed in inoculated soil samples, with crosstalk between microbial gene functions and pepper fruit metabolism. The reformed structure and function of rhizosphere microbial communities were closely associated with pepper fruit quality. Our findings indicate that S. pactum Act12-mediated interactions between rhizosphere microbial communities and pepper plants are responsible for intricate fruit metabolic reprogramming patterns, which enhance not only overall fruit quality but also consumer acceptability.

Dual RNA and 16S ribosomal DNA sequencing reveal arbuscular mycorrhizal fungi-mediated mitigation of selenate stress in Zea mays L. and reshaping of soil microbiota.

Excessively high concentrations of selenium (Se) in soil are toxic to crop plants, and inoculation with arbuscular mycorrhizal fungi (AMF) can reverse Se stress in maize (Zea mays L.). To investigate the underlying mechanisms, maize seedlings were treated with sodium selenate (5 mg Se[VI] kg-1) and/or AMF (Funneliformis mosseae and Claroideoglomus etunicatum). Dual RNA sequencing in mycorrhiza and 16 S ribosomal DNA sequencing in soil were performed. The results showed that Se(VI) application alone decreased plant dry weight, but increased plant Se concentration, total Se content (mainly selenocysteine), and root superoxide content. Inoculation with either F. mosseae or C. etunicatum increased plant dry weight, decreased Se accumulation and selenocysteine proportion, enhanced root peroxidase activity, and alleviated oxidative stress in Se(VI)-treated plants. Inoculation also downregulated the expression of genes encoding Se transporters, assimilation enzymes, and cysteine-rich receptor-like kinases in Se(VI)-stressed plants, similar to plant-pathogen interaction and glutathione metabolism related genes. Conversely, genes encoding selenium-binding proteins and those related to phenylpropanoid biosynthesis were upregulated in inoculated plants under Se(VI) stress. Compared with Se(VI)-free plants, Se tolerance index, symbiotic feedback percentage on plant dry weight, and root colonization rate were all increased in inoculated plants under Se(VI) stress, corresponding to upregulated expression of 'key genes' in symbiosis. AMF inoculation increased bacterial diversity, decreased the relative abundances of selenobacteria related to plant Se absorption (e.g., Proteobacteria and Firmicutes), and improved bacterial network complexity in Se(VI)-stressed soils. We suggest that stress-mediated enhancement of mycorrhizal symbiosis contributed to plant Se(VI) tolerance, whereas AMF-mediated reshaping of soil bacterial community structure prevented excessive Se accumulation in maize.

Liquid Organic Fertilizer Amendment Alters Rhizosphere Microbial Community Structure and Co-occurrence Patterns and Improves Sunflower Yield Under Salinity-Alkalinity Stress.

Response of rhizosphere microbial community structure and co-occurrence patterns to liquid organic fertilizer in sunflower cropland was investigated. Moderate and severe saline-alkaline soils were treated with liquid organic fertilizer containing mainly small molecular organic compounds (450 g L-1) at a rate of 4500 L ha-1 year-1 over 2 years. Compared with the untreated soils, organic fertilizer treatment increased soil nutrient concentrations by 13.8-137.1% while reducing soil pH and salinity by 5.6% and 54.7%, respectively. Organic fertilizer treatment also improved sunflower yield, plant number, and plant height by 28.6-67.3%. Following organic fertilizer treatment, fungal α-diversity was increased, and the effects of salinity-alkalinity stress on rhizosphere microbial communities were alleviated. The relative abundances of some halotolerant microbes and phytopathogenic fungi were reduced in organic fertilizer-treated soils, in contrast to increases in the relative abundances of plant growth-promoting microbes and organic matter decomposers, such as Nocardioides, Rhizophagus, and Stachybotrys. Network analysis revealed that severe salinity-alkalinity stress stimulated cooperation among bacteria, while organic fertilizer treatment tended to stimulate the ecosystem functions of fungi with higher proportions of fungi-bacteria and fungi-fungi links. More keystone taxa (e.g., Amycolatopsis, Variovorax, and Gemmatimonas) were positively correlated with soil nutrient concentrations and crop yield-related traits in organic fertilizer-treated soils. Overall, liquid organic fertilizer amendment could attenuate the adverse effects of salinity-alkalinity stress on sunflower yield by improving soil quality and optimizing rhizosphere microbial community structure and co-occurrence patterns.

Genomic Analysis Reveals Potential Mechanisms Underlying Promotion of Tomato Plant Growth and Antagonism of Soilborne Pathogens by Bacillus amyloliquefaciens Ba13.

Bacillus amyloliquefaciens Ba13 is a plant beneficial bacterium isolated from loessial soil with notable biological activity. This study clarified potential mechanisms underlying the plant growth-promoting and antipathogenic effects of strain Ba13. A pot experiment was used to verify the plant growth-promoting effects of strain Ba13 on tomato, and the antipathogenic activity was tested in petri dishes. The underlying mechanisms were explored based on whole-genome sequencing of strain Ba13 and liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection of plant hormones and biosynthetic intermediates. The results showed that exposure to strain Ba13 promoted tomato plant growth significantly. Compared with control treatment, bacterial treatment increased plant height and fresh weight by 10.98% and 20.15%, respectively, at 28 days after inoculation. Strain Ba13 exhibited antagonistic activity against all eight plant pathogens tested. The 3,861,210-bp genome of strain Ba13 was predicted to encode antibiotics (e.g., surfactin, bacillaene, bacillomycin D, bacilysin, and bacillibactin) and volatile gaseous compounds (e.g., 2,3-butanediol and acetoin). Genes were also predicted to encode extracellular phytase and ß-glucanase that are secreted through the secretory (Sec) system. Strain Ba13 could synthesize indole-3-acetic acid through the indole-3-pyruvic acid pathway. The results of this study indicate that B. amyloliquefaciens Ba13 has multiple effects on tomato plants and associated microorganisms, directly or indirectly promoting plant growth and controlling plant diseases. IMPORTANCE Microbial agents are considered the optimal alternative for chemical agents. Exploring the mechanisms underlying the beneficial effects of microbial agents is essential for rational applications in the field. In this study, we report a functional bacterial strain, Bacillus amyloliquefaciens Ba13, which exhibited plant growth-promoting and antipathogenic effects. The whole genome of strain Ba13 was sequenced, and functional genes of interest were predicted. Strain Ba13 could synthesize indole-3-acetic acid through the indole-3-pyruvic acid pathway.

[Biocontrol effect and mechanism of Bacillus laterosporus Bl13 against early blight disease of tomato]. / 侧孢芽孢杆菌Bl13å¯¹ç•ªèŒ„æ—©ç–«ç— é˜²æ²»æ•ˆæžœåŠæœºåˆ¶.

Bacillus laterosporus Bl13 has good antagonistic effect on the pathogen of tomato early blight (TEB) disease. A pot experiment was conducted to investigate the effect and mechanism of B. laterosporus Bl13 against TEB disease by measuring biological traits such as plant height, stem diameter, disease index of TEB, activity of plant defense enzyme in leaves, and microbial diversity and community composition in root area. The results showed that B. laterosporus Bl13 could significantly reduce the disease index of TEB disease incidence, increase the activity of defensive enzymes including polyphenol oxidase (PPO) and peroxidase (POD) in leaves, and reduce the effects of the disease on the aboveground and root growth of tomato. Meanwhile, B. laterosporus Bl13 improved soil microbial community structure in the root zone, by significantly increasing the relative abundance of plant growth-promoting bacteria (Bacillus and Pseudomonas) and decreasing that of Olpidium and Haematonectria. The results showed that B. laterosporus Bl13 could enhance plant resistance against TEB disease through improving the activity of defensive enzymes in tomato leaves and increasing the number of beneficial microbes in the root zone.

Biocontrol of Root Diseases and Growth Promotion of the Tuberous Plant Aconitum carmichaelii Induced by Actinomycetes Are Related to Shifts in the Rhizosphere Microbiota.

Soil Actinomycetes have been used as biocontrol agents against soil-borne plant diseases, yet little is known about their effects on the structure of the rhizosphere microbiota and the long-term effects on crop yield and disease intensity after the application of Actinomycetes is stopped. Here, we conducted 3-year plot experiments to investigate the roles of two Actinomycetes strains (Streptomyces pactum Act12 and Streptomyces rochei D74) in the biocontrol of soil-borne root diseases and growth promotion of monkhood (Aconitum carmichaelii). We also examined their long-term effects after soil application of a mixed Actinomycetes preparation (spore powder) was completed. High-throughput sequencing was used to analyze shifts in the rhizosphere microbiota. The antifungal activity and root colonization ability of the two Actinomycetes were also tested. Disease severity of southern blight and root rot decreased following application of the Actinomycetes preparation, whereas biomass yield of tubers increased compared with the control group. Significant effects of disease control and plant growth promotion were also observed after application was stopped. The Actinomycetes preparation induced marked increases in the abundance of beneficial microbes and decreases in the abundance of harmful microbes in rhizosphere soil. Adding cell-free culture filtrates of both strains Act12 and D74 inhibited the growth of fungal pathogens capable of causing southern blight (Sclerotium rolfsii) and root rot (Fusarium oxysporum) in A. carmichaelii. A GFP-labeled strain was used to show that D74 can colonize roots of A. carmichaelii. In conclusion, a preparation of two Actinomycetes plays a role in the biocontrol of root diseases and growth promotion of A. carmichaelii by inhibiting pathogen growth and shaping the rhizosphere microbiota.

Saccharopolyspora qinghaiensis sp. nov., a novel actinobacterium isolated from a salt lake.

A novel halophilic, Gram-positive and aerobic actinobacterium, designated strain AFM 20147T, was isolated from a sediment sample collected from Xiaochaidan Salt Lake of Qinghai, China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain AFM 20147T belongs to the genus Saccharopolyspora, shows high sequence similarities to Saccharopolyspora griseoalba AFM 10238T (99.41%) and Saccharopolyspora halophila YIM 90500T (98.20%), and has low similarities (below 98.0%) with other members of the genus. The DNA-DNA relatedness values of strain AFM 20147T with S. griseoalba AFM 10238T and S. halophila YIM 90500T were 40 ± 1.7% and 37 ± 2.3%, respectively. Optimal growth was found to occur at 28 °C, pH 7.5 and in the presence of 7.5% (w/v) NaCl. Strain AFM 20147T was found to contain meso-diaminopimelic acid as the cell wall diamino acid, and galactose and arabinose as the whole cell sugars. The major fatty acids were identified as iso-C15:0, iso-C16:0 and anteiso-C17:0. The major polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylinositol and phosphatidylcholine. MK-9(H4) was found to be the predominant menaquinone and the DNA G+C content was determined to be 67.8 mol%. DNA-DNA relatedness data, together with phenotypic and chemotaxonomic differences, clearly distinguish the isolate from its close neighbours. On the basis of the data from this polyphasic analysis, a novel species Saccharopolyspora qinghaiensis sp. nov. is proposed. The type strain is S. qinghaiensis AFM 20147T (=KCTC 49190T =CGMCC 4.7556T).

Exploring the Abundance and Diversity of Bacterial Communities and Quantifying Antibiotic-Related Genes Along an Elevational Gradient in Taibai Mountain, China.

Thus far, no studies have investigated the soil microbial diversity over an elevational gradient in Taibai Mountain, the central massif of the Qinling Mountain Range. Here, we used Illumina sequencing and quantitative PCR of the 16S rRNA gene to assess the diversity and abundance of bacterial communities along an elevational gradient in representative vegetation soils in Taibai Mountain. We identified the soil, climate, and vegetation factors driving the variations in soil bacterial community structure by Pearson correlation and redundancy analysis. We also evaluated the potential for antibiotic discovery by quantitative PCR of the PKS-I, PKS-II, and NRPS genes from Actinobacteria. The results showed that soil bacterial alpha diversity increased first and then decreased with an elevational rise in both the northern and southern slopes of Taibai Mountain. The bacterial abundance was significantly correlated with soil organic matter and nitrate nitrogen. The average relative abundance of Actinobacteria in Taibai Mountain was markedly higher than those in other mountain forest soils. The absolute abundance of PKS and NPRS gene was significantly higher in the tested soils compared with the gene copy numbers reported in tropical urban soils. Taibai Mountain is rich in actinomycete resources and has great potential for antibiotic excavation.

Reclassification of Mzabimyces algeriensis Saker et al. 2015 as Halopolyspora algeriensis comb. nov.

Halopolyspora alba AFM10251T was proposed to represent a novel species of a new genus belonging to the family Actinopolysporaceae in a previous study. The family Mzabimycetaceae , containing one genus, Mzabimyces, was proposed subsequently and Mzabimyces algeriensis H195T was the type strain. However, analysis of 16S rRNA gene sequence similarity showed that the two strains were highly similar (99.2 %). Phenotypic and chemotaxonomic data, as well as DNA-DNA hybridization confirmed that the two strains are different genomic species of the same genus, Halopolyspora. Mzabimyces algeriensis should be classified in the genus Halopolyspora as Halopolysporaalgeriensis comb. nov. The type strain of Halopolysporaalgeriensis is H195T (=DSM 46680T=CECT 8575T).

Haloactinomyces albus gen. nov., sp. nov., isolated from the Dead Sea.

A novel halophilic, filamentous actinomycete strain, designated AFM 10258T, was isolated from a sediment sample collected from the Dead Sea of Israel. The isolate grew with 10-35 % NaCl and did not grow without NaCl. The isolate formed white aerial mycelium and long spore chains, and two spores were separated by sterile mycelium. The spores were non-motile, spherical and rugose-surfaced. The isolate contained meso-diaminopimelic acid as the diagnostic diamino acid and galactose and arabinose as the major whole-cell sugars. The polar lipids were diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and three unknown phospholipids. Major fatty acids were anteiso-C17 : 0, iso-C16 : 0 and iso-C15 : 0. MK-9(H4) was the predominant menaquinone and the DNA G+C content was 62.8 mol%. 16S rRNA gene sequence analysis indicated that strain AFM 10258T shared low sequence similarity with the closely related representatives of the families Pseudonocardiaceae (below 94.47 %) and Actinopolysporaceae (below 93.76 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain AFM 10258T formed a robust clade with members of the family Actinopolysporaceae. On the basis of analysis of phenotypic, chemical and molecular characteristics, strain AFM 10258T is considered to represent a novel species of a new genus, for which the name Haloactinomyces albus gen. nov., sp. nov., is proposed. The type strain is AFM 10258T (=DSM 45977T=CGMCC 4.7115T).

Production of lipopeptide biosurfactants by Bacillus atrophaeus 5-2a and their potential use in microbial enhanced oil recovery.

BACKGROUND: Lipopeptides are known as promising microbial surfactants and have been successfully used in enhancing oil recovery in extreme environmental conditions. A biosurfactant-producing strain, Bacillus atrophaeus 5-2a, was recently isolated from an oil-contaminated soil in the Ansai oilfield, Northwest China. In this study, we evaluated the crude oil removal efficiency of lipopeptide biosurfactants produced by B. atrophaeus 5-2a and their feasibility for use in microbial enhanced oil recovery. RESULTS: The production of biosurfactants by B. atrophaeus 5-2a was tested in culture media containing eight carbon sources and nitrogen sources. The production of a crude biosurfactant was 0.77 g L-1 and its surface tension was 26.52 ± 0.057 mN m-1 in a basal medium containing brown sugar (carbon source) and urea (nitrogen source). The biosurfactants produced by the strain 5-2a demonstrated excellent oil spreading activity and created a stable emulsion with paraffin oil. The stability of the biosurfactants was assessed under a wide range of environmental conditions, including temperature (up to 120 °C), pH (2-13), and salinity (0-50 %, w/v). The biosurfactants were found to retain surface-active properties under the extreme conditions. Additionally, the biosurfactants were successful in a test to simulate microbial enhanced oil recovery, removing 90.0 and 93.9 % of crude oil adsorbed on sand and filter paper, respectively. Fourier transform infrared spectroscopy showed that the biosurfactants were a mixture of lipopeptides, which are powerful biosurfactants commonly produced by Bacillus species. CONCLUSIONS: The study highlights the usefulness of optimization of carbon and nitrogen sources and their effects on the biosurfactants production and further emphasizes on the potential of lipopeptide biosurfactants produced by B. atrophaeus 5-2a for crude oil removal. The favorable properties of the lipopeptide biosurfactants make them good candidates for application in the bioremediation of oil-contaminated sites and microbial enhanced oil recovery process.

Saccharopolyspora griseoalba sp. nov., a novel actinomycete isolated from the Dead Sea.

A novel halotolerant actinomycete, designated strain AFM 10238T, was isolated from a sediment sample collected from the Dead Sea of Israel. The isolate grew at 15-45 °C, pH 6-12 and with 0-15 % (w/v) NaCl. Strain AFM 10238T contains meso-diaminopimelic acid as cell wall diamino acid, and galactose and arabinose as the whole cell sugars. The major polar lipids are phosphatidylcholine, phosphatidylglycerol, and diphosphatidylglycerol. Major fatty acids are iso-C16:0, iso-C17:0, iso-C15:0, anteiso-C17:0 and C17:1 ω8c. MK-9(H4) is the predominant menaquinone and the DNA G + C content is 72.7 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain AFM10238T belongs to the genus Saccharopolyspora. The 16S rRNA gene sequence similarity between strain AFM 10238T and its close neighbours, Saccharopolyspora halophila YIM 90500T , Saccharopolyspora spinosa DSM 44228T, Saccharopolyspora dendranthemae KLBMP 1305T and Saccharopolyspora cebuensis DSM 45019T were 98.2, 97.2, 97.1 and 97.0 %, respectively. Sequence similarities to other type strains of this genus were below 97 %. DNA-DNA relatedness data, together with phenotypic and chemotaxonomic differences, clearly distinguished the isolate from its close neighbours. On the basis of the data from this polyphasic analysis, a novel species Saccharopolyspora griseoalba sp. nov. is proposed. The type strain is AFM 10238T (= DSM 46,663 = CGMCC 4.7124).

Amycolatopsis flava sp. nov., a halophilic actinomycete isolated from Dead Sea.

A novel halophilic, filamentous actinomycete, designated strain AFM 10111(T), was isolated from a sediment sample collected from the Dead Sea of Israel and its taxonomic position was established by using a polyphasic taxonomic approach. The isolate grew at 20-35 °C, pH 5-12 and with 1-30 % NaCl. The substrate mycelium is white or yellow, well developed, branched and fragments into squarish, rod-like elements. The isolate contained meso-diaminopimelic acid as cell-wall diamino acid, and arabinose and galactose as whole-cell sugars. The major menaquinone was MK-9(H4). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine phosphatidylmethylethanolamine and one unidentified phospholipid. Major fatty acids were iso-C16:0, iso-C16:1 H, C17:1 ω6c. The DNA G + C content was 67.7 mol %. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain AFM 10111(T) belongs to the genus Amycolatopsis, and formed a distinct clade with Amycolatopsis marina CGMCC 4.3568(T) and Amycolatopsis palatopharyngis CGMCC 4.1729(T), with the sequence similarity 98.4 and 98.6 %. The level of DNA-DNA relatedness between the strain AFM 10111(T) and A. marina CGMCC 4.3568(T) and A. palatopharyngis CGMCC 4.1729(T) were 46.9 ± 3.08 and 49.4 ± 1.25 %. The combined genotypic and phenotypic data indicate that strain AFM 10111(T) represents a novel species of the genus Amycolatopsis, for which the name Amycolatopsis flava sp. nov. is proposed. The type strain is AFM 10111(T) (= DSM 46658(T) = CGMCC 4.7123(T)).

Paenibacillus quercus sp. nov., isolated from rhizosphere of Quercus aliena var. acuteserrata.

A Gram-positive, spore-forming, rod-shaped and motile bacterium, designated strain 1-25(T), was isolated from the rhizosphere of Quercus aliena var. acuteserrata in Taibai Mountain, Shaanxi Province, China. 16S rRNA gene sequence analysis showed that strain 1-25(T) belongs to the genus Paenibacillus. Strain 1-25(T) was found to be closely related to Paenibacillus harenae and Paenibacillus castaneae with 96.0 and 95.9 % 16S rRNA gene sequence similarities, respectively. The strain was observed to grow optimally at 28 °C and pH 7.5. The major isoprenoid quinone was found to be menaquinone-7. The dominant cellular fatty acids were identified as anteiso-C15:0 and iso-C15:0. The diagnostic diamino acid in the cell-wall peptidoglycan was found to be meso-diaminopimelic acid. The DNA G+C content was determined to be 41.6 mol%. On the basis of phenotypic characteristics and molecular properties, strain 1-25(T) is considered to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus quercus sp. nov. is proposed. The type strain is 1-25(T) (=CCTCC AB2013265(T) = KCTC 33194(T)).

Halopolyspora alba gen. nov., sp. nov., isolated from sediment.

A novel halophilic, filamentous actinomycete, designated strain AFM 10251(T), was isolated from a sediment sample collected from the Dead Sea, Israel. The isolate grew with 10-35% multi-salts, and did not grow without NaCl or MgCl2. The isolate formed a white aerial mycelium, and long chains of arthrospores with more than 10 spores per chain. The spores were spherical or oval with warty surfaces, and sterile mycelium was present between individual spores. The isolate contained meso-diaminopimelic acid and a small proportion of LL-diaminopimelic acid as cell-wall diamino acids, and galactose and arabinose as whole-cell sugars. The major menaquinone was MK-9(H4). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and three unknown phospholipids. Major fatty acids were iso-C(16 : 0), iso-C(17 : 0), iso-C(15 : 0) and anteiso-C(17 : 0). The DNA G+C content of strain AFM 10251(T) was 66.7 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain AFM 10251(T) and the genus Actinopolyspora formed a distinct lineage. Analysis of the secondary structures of variable areas of the 16S rRNA gene showed that strain AFM 10251(T) was different from all recognized species of the genus Actinopolyspora and members of the family Pseudonocardiaceae. Analysis of the signature nucleotides of the 16S rRNA gene showed that strain AFM 10251(T) and Actinopolyspora halophila formed a single group, but with base pair differences at positions 127 : 234 and 183 : 194. On the basis of analysis of chemical and molecular characteristics, strain AFM 10251(T) is considered to represent a novel species of a new genus in the family Actinopolysporaceae, for which the name Halopolyspora alba gen. nov., sp. nov. is proposed. The type strain of Halopolyspora alba is AFM 10251(T) ( = DSM 45976(T) = CGMCC 4.7114(T)).

Methylobacterium soli sp. nov. a methanol-utilizing bacterium isolated from the forest soil.

A Gram-negative, pink-pigmented, non-spore-forming rod shaped, methanol-utilizing bacterium, strain YIM 48816(T), was isolated from forest soil collected from Sichuan province, China. Strain YIM 48816(T) can grow at 4-37 °C, pH 5.0-7.0 and 0% NaCl (w/v). Based on 16S rRNA gene sequence similarity studies, it belonged to the genus Methylobacterium, and formed a phyletic line. The 16S rRNA gene sequence similarities were 96.2% to Methylobacterium mesophilicum DSM 1708(T) and 96.0% to Methylobacterium brachiatum DSM 19569(T), and the phylogenetic similarities to all other Methylobacterium species with validly published names were less than 96.0%. The major menaquinones detected were Q-10 (97.14%) and Q-9 (2.86%). The major fatty acids were C18:1 ω7c (80.84%). The DNA G + C content was 66.2 mol%. It is apparent from the genotypic and phenotypic data that strain YIM 48816(T) belongs to a novel species of the genus Methylobacterium, for which the name Methylobacterium soli sp. nov. is proposed. The type strain is YIM 48816(T) (CCTCC AA 208027(T) = KCTC 22810(T)).

Planosporangium mesophilum sp. nov., isolated from rhizosphere soil of Bletilla striata.

A Gram-stain-positive, non-motile actinomycete, designated strain YIM 48875(T), was isolated from rhizosphere soil of Bletilla striata and its taxonomic position was established by using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequence data showed that strain YIM 48875(T) belonged to the genus Planosporangium, supported by a bootstrap value of 100 %. Cells of strain YIM 48875(T) showed two kinds of sporangia, which also supported its classification in the genus Planosporangium. Strain YIM 48875(T) grew optimally at 28 °C, at pH 6.0-8.0 and in the presence of 2 % (w/v) NaCl. The level of 16S rRNA gene sequence similarity between strain YIM 48875(T) and Planosporangium flavigriseum YIM 46034(T) was 98.6 %. Strain YIM 48875(T) exhibited a quinone system with menaquinones MK-9(H(4)), MK-9(H(6)) and MK-9(H(8)) as the predominant compounds, a polar lipid profile comprising diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol mannoside and the major fatty acids iso-C(15 : 0) and iso-C(16 : 0); these data were markedly different from those for P. flavigriseum YIM 46034(T). The level of DNA-DNA relatedness between strain YIM 48875(T) and P. flavigriseum YIM 46034(T) was 45.5 %. It is apparent from the genotypic and phenotypic data that strain YIM 48875(T) represents a novel species of the genus Planosporangium, for which the name Planosporangium mesophilum sp. nov. is proposed. The type strain is YIM 48875(T) ( = CCTCC AA 209049(T)  = KCTC 19779(T)).

[Distribution and characteristics of soil antagonistic actinomycetes on northern slope of Taibai Mountain, Qinling].

Twelve representative soil samples were collected from different altitudes on the northern slope of Taibai Mountain to study the distribution and characteristics of soil antagonistic actinomyces by using agar block method. There existed a great deal of soil antagonistic actinomyces in the study area. Among the 141 actinomycete strains isolated, 116 strains (82.3%) showed antagonism toward 12 target bacteria or fungi. The antagonistic strains at altitudes 800-1845, 3488, 3655, and 3670 m occupied 73.7% -86.8%, 81.3%, 78.9% and 82.3% of the total, respectively. 42.1% of the strains at altitudes 1200-2300 m and > 3400 m showed strong and broad spectrum antagonistic activity, suggesting that there was a great potential for the isolation of actinomycete strains with strong anti-biotic capability at these altitudes. 24.1% of the antagonistic actinomycetes showed antagonism against Staphyloccocus aureu, and 2.4%, 6.9% and 11.2% of them showed activity toward Verticillium dahliae in cotton, Phytophthora sp. in strawberry and Neonectria radiciccla in ginseng, respectively. This study showed that the soil actinomycete antagonistic potentiality (SAAP) could be used as a quantitative indicator to evaluate the potential of antagonistic actinomycete resources in soil.