Eco-friendly management of Meloidogyne incognita in cadmium-contaminated soil by using nematophagous fungus Purpureocillium lavendulum YMF1.683: Efficacy and mechanism.

Root-knot nematodes (RKNs) are distributed globally, including in agricultural fields contaminated by heavy metals (HM), and can cause serious crop damages. Having a method that could control RKNs in HM-contaminated soil while limit HM accumulation in crops could provide significant benefits to both farmers and consumers. In this study, we showed that the nematophagous fungus Purpureocillium lavendulum YMF1.683 exhibited a high nematocidal activity against the RKN Meloidogyne incognita and a high tolerance to CdCl2. Comparing to the P. lavendulum YMF1.838 which showed low tolerance to Cd2+, strain YMF1.683 effectively suppressed M. incognita infection and significantly reduced the Cd2+ uptake in tomato root and fruit in soils contaminated by 100 mg/kg Cd2+. Transcriptome analyses and validation of gene expression by RT-PCR revealed that the mechanisms contributed to high Cd-resistance in YMF1.683 mainly included activating autophagy pathway, increasing exosome secretion of Cd2+, and activating antioxidation systems. The exosomal secretory inhibitor GW4869 reduced the tolerance of YMF1.683 to Cd2+, which firstly demonstrated that fungal exosome was involved in HM tolerance. The up-regulation of glutathione synthesis pathway, increasing enzyme activities of both catalase and superoxide dismutase also played important roles in Cd2+ tolerance of YMF1.683. In Cd2+-contaminated soil, YMF1.683 limited Cd2+-uptake in tomato by up-regulating the genes of ABCC family in favor of HM sequestration in plant, and down-regulating the genes of ZIP, HMA, NRAMP, YSL families associated with HM absorption, transport, and uptake in plant. Our results demonstrated that YMF1.683 could be a promising bio-agent in eco-friendly management of M. incognita in Cd2+ contaminated soils.

2-Furoic acid associated with the infection of nematodes by Dactylellina haptotyla and its biocontrol potential on plant root-knot nematodes.

Dactylellina haptotyla is a typical nematode-trapping fungus that has garnered the attention of many scholars for its highly effective lethal potential for nematodes. Secondary metabolites play an important role in D. haptotyla-nematode interactions, but which metabolites perform which function remains unclear. We report the metabolic functions based on high-quality, chromosome-level genome assembly of wild D. haptotyla YMF1.03409. The results indicate that a large variety of secondary metabolites and their biosynthetic genes were significantly upregulated during the nematode-trapping stage. In parallel, we identified that 2-furoic acid was specifically produced during nematode trapping by D. haptotyla YMF1.03409 and isolated it from fermentation production. 2-Furoic acid demonstrated strong nematicidal activity with an LD50 value of 55.05 µg/mL against Meloidogyne incognita at 48 h. Furthermore, the pot experiment showed that the number of galls of tomato root was significantly reduced in the experimental group treated with 2-furoic acid. The considerable increase in the 2-furoic acid content during the infection process and its virulent nematicidal activity revealed an essential synergistic effect during the process of nematode-trapping fungal infection. IMPORTANCE Dactylellina haptotyla have significant application potential in nematode biocontrol. In this study, we determined the chromosome-level genome sequence of D. haptotyla YMF1.03409 by long-read sequencing technology. Comparative genomic analysis identified a series of pathogenesis-related genes and revealed significant gene family contraction events during the evolution of D. haptotyla YMF1.03409. Combining transcriptomic and metabolomic data as well as in vitro activity test results, a compound with important application potential in nematode biocontrol, 2-furoic acid, was identified. Our result expanded the genetic resource of D. haptotyla and identified a previously unreported nematicidal small molecule, which provides new options for the development of plant biocontrol agents.

Vermicomposting of Pleurotus eryngii spent mushroom substrates and the possible mechanisms of vermicompost suppressing nematode disease caused by Meloidogyne incognita.

The mushroom industry produces a large amount of spent mushroom substrate (SMS), which requires a large geographical footprint and causes pollution. Vermicomposting is a low-cost technology for its value in recycling of organic wastes and production of beneficial organic fertilizers. In this study, the changes of physicochemical properties was characterized during vermicomposting of Pleurotus eryngii SMS with cow dung (CD) as amendment. The efficiency and possible mechanisms of vermicompost suppressing disease induced by Meloidogyne incognita was also investigated. Six combinations with different ratios of SMS and cow dung (CD) was included in the vermicomposting using Eisenia fetida. Effect of vermicompost against disease induced by M. incognita on tobacco was conducted under greenhouse condition. And the possible mechanisms of vermicompost suppressing M. incognita was investigated by evaluated the species diversity of nematode-trapping fungi (NTF) in soil, and the defense response enzymes in tobacco. The combination of 65% SMS +35% CD was more suitable for vermicomposting, in which the highest vermicompost production (57%) and earthworm biomass increment (268%) were achieved. Additionally, the reduction in pH, total organic carbon, carbon: nitrogen ratio, and the pronounced elevation in four overall nutrient status were also observed. Soil amended with vermicompost (100:1 w/w) showed 61% control efficiency against nematode disease caused by M. incognita on tobacco, which significantly higher than that of the normal compost (24%). Comparing to the normal compost, the potential mechanism of vermicompost suppressing M. incognita could be rely on promoting species diversity of NTF in soil and enhancing the activities of the defense response enzymes in tobacco plant. Our findings indicate that vermicomposting is a promising technology for recycling of P. eryngii SMS, and the resulting vermicompost as organic fertilizer can be sued for management of the diseases caused by root-knot nematodes. This study establish a sustainable avenue for P. eryngii SMS disposal and a practical manner for controlling pathogens.

Characterization of the complete mitochondrial genome of the nematode-trapping fungus Drechslerella dactyloides.

The complete mitochondrial genome of Drechslerella dactyloides was characterized in this study. This mitogenome is a closed circular molecule of 246860 bp in length with a GC content of 26.16%, including 87 predicted protein-coding genes, 29 transfer RNA genes, and two rRNA gens. Phylogenetic analyses based on concatenated amino acid sequences at 14 conserved mitochondrial protein-coding genes showed that D. dactyloides was closely related to Dactylellina haptotyla.

Sphingobacterium faecale sp. nov., a 1-aminocyclopropane-1-carboxylate deaminase producing bacterium isolated from camel faeces.

An investigation of the diversity of 1-aminocyclopropane-1-carboxylate deaminase producing bacteria associated with camel faeces revealed the presence of a novel bacterial strain designated C459-1T. It was Gram-stain-negative, short-rod-shaped and non-motile. Strain C459-1T was observed to grow optimally at 35 °C, at pH 7.0 and in the presence of 0 % NaCl on Luria-Bertani agar medium. The cells were found to be positive for catalase and oxidase activities. The major fatty acids (>10 %) were identified as iso-C15 : 0, summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c) and iso-C17 : 0 3-OH. The predominant menaquinone was MK-7. The major polar lipids consisted of phosphatidylethanolamine, one sphingophospholipid, two unknown aminophospholipids, three unknown glycolipids and five unknown lipids. The genomic DNA G+C content was 40.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain C459-1T was affiliated with the genus Sphingobacterium and had the highest sequence similarity to Sphingobacterium tabacisoli h337T (97.0 %) and Sphingobacterium paucimobilis HER1398T (95.6 %). The average nucleotide identity and digital DNA-DNA hybridization values between strain C459-1T and S. tabacisoli h337T were 83.8 and 33.8 %, respectively. Phenotypic characteristics including enzyme activities and carbon source utilization differentiated strain C459-1T from other Sphingobacterium species. Based on its phenotypic, chemotaxonomic and phylogenetic properties, strain C459-1T represents a novel species of the genus Sphingobacterium, for which the name Sphingobacterium faecale sp. nov. is proposed, with strain is C459-1T (CGMCC 1.18716T=KCTC 82381T) as the type strain.

Survival and infectivity of second-stage root-knot nematode Meloidogyne incognita juveniles depend on lysosome-mediated lipolysis.

Adaptation to nutrient deprivation depends on the activation of metabolic programs to use reserves of energy. When outside a host plant, second-stage juveniles (J2) of the root-knot nematode (Meloidogyne spp.), an important group of pests responsible for severe losses in the production of crops (e.g., rice, wheat, and tomato), are unable to acquire food. Although lipid hydrolysis has been observed in J2 nematodes, its role in fitness and the underlying mechanisms remain unknown. Using RNA-seq analysis, here, we demonstrated that in the absence of host plants, the pathway for the biosynthesis of polyunsaturated fatty acids was upregulated, thereby increasing the production of arachidonic acid in middle-stage J2 Meloidogyne incognita worms. We also found that arachidonic acid upregulated the expression of the transcription factor hlh-30b, which in turn induced lysosomal biogenesis. Lysosomes promoted lipid hydrolysis via a lysosomal lipase, LIPL-1. Furthermore, our data demonstrated that blockage of lysosomal lipolysis reduced both lifespan and locomotion of J2 worms. Strikingly, disturbance of lysosomal lipolysis resulted in a decline in infectivity of these juveniles on tomato roots. Our findings not only reveal the molecular mechanism of lipolysis in J2 worms but also suggest potential novel strategies for the management of root-knot nematode pests.

Effects of organic acids on the chemotaxis profiles and biocontrol traits of antagonistic bacterial endophytes against root-rot disease in Panax notoginseng.

Understanding the role of chemotaxis in ecological interactions between plants and microbes in the rhizosphere is necessary to optimize biocontrol strategies targeting plant soil-borne diseases. Therefore, we examined and profiled the antagonistic endophytic bacteria (AEB) population with chemotaxis potential in the medicinal plant Panax notoginseng using a cheA gene-based approach coupled with 16S rRNA sequencing. Phylogenetic analysis of the chemotactic AEB (CAEB) community in P. notoginseng enabled the identification of 56 CAEB strains affiliated with 30 species of Actinobacteria, Firmicutes, and Proteobacteria; Firmicutes, especially Bacillus, were predominant. We then systematically quantified the chemotactic response profiles of CAEB toward five organic acid (OA) attractants: citric acid, fumaric acid (FA), malic acid, oxalic acid, and succinic acid. Further hierarchical cluster analysis revealed that the chemotaxis of CAEB to the same attractant exhibited different patterns among not only genera but also species and even strains of the same species. Following chemotaxis and hierarchical analysis, we selected the strongest chemoattractant, fumaric acid (FA), as the target for evaluating the effects of OAs on the representative CAEB strain Bacillus amyloliquefaciens subsp. plantarum YP1. Application of FA significantly stimulated the chemotaxis ability and growth of YP1, and increased the transcript levels of cheA and biocontrol-related genes in YP1. This is the first study to characterise the diversity of chemotaxis profiles toward OAs in natural bacterial assemblages of P. notoginseng and to highlight how FA promotes the biocontrol-related traits of P. notoginseng-associated CAEB.

Fungistatic Mechanism of Ammonia against Nematode-Trapping Fungus Arthrobotrys oligospora, and Strategy for This Fungus To Survive Ammonia.

Soil fungistasis is a phenomenon in which the germination and growth of fungal propagules is widely inhibited in soils. Although fungistatic compounds are known to play important roles in the formation of soil fungistasis, how such compounds act on soil fungi is little studied. In this study, it was found that ammonia (NH3) induced global protein misfolding marked by increased ubiquitination levels of proteins (ubiquitylome data and Western blot verification). The misfolded proteins should trigger the endoplasmic reticulum (ER) stress, which was indicated by electron microscope image and proteome data. Results from the mutants of BiP and proteasome subunit alpha 7 suggested that ER stress played a mechanistic role in inhibiting conidial germination. Results from proteome data indicated that, to survive ammonia fungistasis, conidia first activated the unfolded protein response (UPR) to decrease ER stress and restore ER protein homeostasis, and the function of UPR in surviving ammonia was confirmed by using mutant strains. Second, ammonia toxicity could be reduced by upregulating carbon metabolism-related proteins, which benefited ammonia fixation. The results that metabolites (especially glutamate) could relieve the ammonia fungistasis confirmed this indirectly. Finally, results from gene knockout mutants also suggested that the fungistatic mechanism of ammonia is common for soil fungistasis. This study increased our knowledge regarding the mechanism of soil fungistasis and provided potential new strategies for manipulating soil fungistasis. IMPORTANCE Soil fungistasis is a phenomenon in which the germination and growth of fungal propagules is widely inhibited in soil. Although fungistatic compounds are known to play important roles in the formation of soil fungistasis, how such compounds act on soil fungi remains little studied. This study revealed an endoplasmic reticulum stress-related fungistatic mechanism with which ammonia acts on Arthrobotrys oligospora and a survival strategy of conidia under ammonia inhibition. Our study provides the first mechanistic explanation of how ammonia impacts fungal spore germination, and the mechanism may be common for soil fungistasis. This study increases our knowledge regarding the mechanism of soil fungistasis in fungal spores and provides potential new strategies for manipulating soil fungistasis.

Methylglyoxal Has Different Impacts on the Fungistatic Roles of Ammonia and Benzaldehyde, and Lactoylglutathione Lyase Is Necessary for the Resistance of Arthrobotrys oligospora to Soil Fungistasis.

Biocontrol of root-knot nematode has attracted increasing attention over the past two decades. The inconsistent field performance of biocontrol agents, which is caused by soil fungistasis, often restricts their commercial application. There is still a lack of research on the genes involved in biocontrol fungi response to soil fungistasis, which is important for optimizing practical applications of biocontrol fungi. In this study, the lactoylglutathione lyase-encoding AOL_s00004g335 in the nematophagous fungi Arthrobotrys oligospora was knocked out, and three mutant strains were obtained. The hyphal growth of mutants on the three media was almost the same as that of the wild-type strain, but mutants had slightly higher resistance to NaCl, SDS, and H2O2. Methylglyoxal (MG) significantly increased the resistance of A. oligospora to ammonia, but decreased the resistance to benzaldehyde. Furthermore, the resistance of the mutants to soil fungistasis was largely weakened and MG could not increase the resistance of A. oligospora to soil fungistasis. Our results revealed that MG has different effects on the fungistatic roles of ammonia and benzaldehyde and that lactoylglutathione lyase is very important for A. oligospora to resist soil fungistasis.

Sphingobacterium lumbrici sp. nov., a novel bacterium isolated from wormcast of Eisenia foetida.

A novel Gram-stain-negative, rod-shaped, non-motile, yellowish bacterium, designated strain 1.3611T, was isolated from the wormcast of Eisenia foetida. The strain grew optimally at 30-37 ℃, at pH 7.0 and with 0-1.0 % (w/v) NaCl. Based on the results of 16S rRNA gene sequence and phylogenetic analyses, strain 1.3611T showed the highest degree of 16S rRNA gene sequence similarity to Sphingobacterium olei HAL-9T (97.0 %), followed by Sphingobacterium alkalisoli Y3L14T (95.8 %). The respiratory quinone of strain 1.3611T was menaquinone-7 (MK-7) and its major cellular fatty acids were iso-C15 : 0 (41.3 %), summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c, 22.1 %) and iso-C17 : 0 3-OH (16.2 %). The major polar lipids were sphingophospholipid, phosphatidylethanolamine, four unidentified glycolipids, two unidentified phospholipids and five unidentified polar lipids. The genomic DNA G+C content was 39.0 mol%. The digital DNA-DNA hybridization and average nucleotide identity values between the genomes of strain 1.3611T and S. olei HAL-9T were 37.9 and 88.9 %, respectively. According to the phenotypic and chemotaxonomic phylogenetic results, strain 1.3611T should represent a novel species of the genus Sphingobacterium, for which the name Sphingobacterium lumbrici sp. nov. is proposed, with strain 1.3611T (=KCTC 62980T=CCTCC AB 2018349T) as the type strain.

Nocardioides stalactiti sp. nov., isolated from a cave stalactite surface.

An aerobic, rod-shaped, Gram-stain-positive, actinobacterial strain, designated 1.0914T, was isolated from a stalactite sample collected from a cave located in Guizhou Province, southwest PR China. Based on 16S rRNA gene sequence analysis, strain 1.0914T shared highest similarities values with Nocardioides pelophilus CGMCC 4.7388T (97.7 %), Nocardioides immobilis CCTCC AB 2017083T (97.5 %) and Nocardioides silvaticus CCTCC AB 2018079T (97.3 %) and values lower than 97.0 % to other members of the genus Nocardioides. Phylogenetic trees based on 16S rRNA gene sequences indicated that strain 1.0914T formed an isolated branch with N. pelophilus CGMCC 4.7388T, N. immobilis CCTCC AB 2017083T and N. silvaticus CCTCC AB 2018079T. The polar lipids contained phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol and one unidentified phospholipid in the cellular membrane. The major fatty acids were identified as iso-C16 : 0, C18 : 1 ω9c, C17 : 1 ω8c and C16 : 0. The predominant respiratory quinone was MK-8(H4) and ll-diaminopimelic acid was the diagnostic diamino acid in the cell-wall peptidoglycan. The genomic DNA G+C content was 71.1 mol%. The orthologous average nucleotide identiy values between N. pelophilus CGMCC 4.7388T, N. immobilis CCTCC AB 2017083T, N. silvaticus CCTCC 2018079T and strain 1.0914T were 82.3, 81.7 and 81.9 % respectively. DNA-DNA hybridization values between N. pelophilus CGMCC 4.7388T, N. immobilis CCTCC AB 2017083T, N. silvaticus CCTCC 2018079T and strain 1.0914T were 25.2, 24.6 and 24.5 % respectively. The phylogenetic, phenotypic and chemotaxonomic data supported the classification of strain 1.0914T as representing a new species of Nocardioides, for which the name Nocardioides stalactiti sp. nov. is proposed. The type strain is 1.0914T (=CCTCC AB 2018266T=KCTC 49243T).

Sphingobacterium cavernae sp. nov., a novel bacterium isolated from soil sampled at Tiandong Cave.

A Gram-stain-negative, non-motile and rod-shaped bacterium, designated strain 5.0403-2T, was isolated from a cave soil sample collected from Tiandong Cave, Guizhou Province, south-west PR China. Cells showed positive oxidase and catalase reactions. The predominant isoprenoid quinone was MK-7. The major fatty acids were identified as iso-C15 : 0, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), iso-C17 : 0 3OH and summed feature 9 (iso-C17 : 1 ω9c or C16 : 0 10-methyl). The cellular polar lipids contained phosphatidylethanolamine, one unidentified phospholipid, three unidentified phosphoglycolipids and four unidentified lipids. The genomic DNA G+C content was 36.0 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain 5.0403-2T should be assigned to the genus Sphingobacterium. Results of 16S rRNA gene sequence similarity analysis showed that strain 5.0403-2T was most similar to Sphingobacterium bovisgrunnientis KCTC 52685T (98.7 %), Sphingobacterium composti KCTC 12578T (98.0 %) and Sphingobacterium alimentarium DSM 22362T (97.3 %) and less than 95.0 % similar to other species of the genus Sphingobacterium. The average nucleotide identity values between strain 5.0403-2T and S. bovisgrunnientis KCTC 52685T, S. composti KCTC 12578T and S. alimentarium DSM 22362T were 94.2, 82.3 and 77.2 % respectively. The digitalDNA-DNA hybridization values between strain 5.0403-2T and S. bovisgrunnientis KCTC 52685T, S. composti KCTC 12578T and S. alimentarium DSM 22362T were 68.4, 25.6 and 20.7 %. These results indicated that the isolate represented a novel genomic species. The polyphasic taxonomic characteristics indicated that strain 5.0304-2T represents a novel species of the genus Sphingobacterium, for which the name Sphingobacterium cavernae sp. nov. (type strain 5.0403-2T=KCTC 62981T=CCTCC AB 2019257T) is proposed.

Luteimonas lumbrici sp. nov., a novel bacterium isolated from wormcast.

A Gram-stain-negative, yellow-green bacterium, designated 1.1416T, was isolated from wormcast of Eisenia foetida. The strain was non-motile, rod-shaped, and grew optimally on NA medium at 30 °C, pH 7.0 and with 0 % (w/v) NaCl. On the basis of the 16S rRNA gene sequence and phylogenetic analysis, 1.1416T showed the highest degree of 16S rRNA gene sequence similarity to Luteimonas arsenica 26-35T (96.2 %), followed by Luteimonas lutimaris G3T (96.1 %). The respiratory quinone of 1.1416T was ubiquinone-8 (Q-8), and its major cellular fatty acids were iso-C15 : 0 (39.8 %), summed feature 9 (iso-C17 : 1 ω9c or C16 : 0 10-methyl) (18.6 %). The major polar lipids of 1.1416T were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and six unidentified phospholipids. The genomic DNA G+C content of 1.1416T was 71.0 mol%. According to the results of the phenotypic and chemotaxonomic phylogenetic analyses, strain 1.1416T represents a novel species of the genus Luteimonas, for which the name Luteimonas lumbrici sp. nov. is proposed, with strain 1.1416T (=KCTC 62979T=CCTCC AB 2018348T) as the type strain.

Asticcacaulis tiandongensis sp. nov., a new member of the genus Asticcacaulis, isolated from a cave soil sample.

A Gram-stain negative, aerobic, motile and rod-shaped bacterium, designated strain 3.1105T, was isolated from a karst district soil sample collected from Tiandong cave, Guizhou province, south-west PR China. The isolate grew at 10-40 °C and pH 5.0-8.0 and tolerated up to 1 % NaCl (w/v) on R2A medium, with optimal growth at 25-30 °C, pH 7.0 and 0 % NaCl (w/v). Cells showed oxidase-positive and catalase-positive reactions. The respiratory quinone was Q-10. The predominant cellular fatty acids contained C18 : 1ω7c 11-methyl, summed feature 8 (C18 : 1ω7c or C18 : 1ω6c), C16 : 0 and C17 : 0. The major polar lipids were phosphatidylglycerol and monoglycosyldiglycerides. The genomic DNA G+C content was 56.0 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that 3.1105T should be affiliated to the genus Asticcacaulis and showed highest 16S rRNA gene sequence similarity values with Asticcacaulis excentricus CB 48T (96.0 %), Asticcacaulis endophyticus ZFGT-14T (95.3 %) and lower than 95.3 % similarity to other species of the genus Asticcacaulis. The polyphasic taxonomic characteristics indicated that strain 3.1105T represents a novel species of the genus Asticcacaulis, for which the name Asticcacaulis tiandongensis sp. nov., (type strain 3.1105T=KCTC 62978T=CCTCC AB 2018268T) is proposed.

Aquabacter cavernae sp. nov., a bacterium isolated from cave soil.

A Gram-stain-negative, rod-shaped, non-motile, aerobic, catalase-negative and oxidase-positive bacterium, designated strain Sn-9-2T, was isolated from a cave soil sample collected from Tiandong cave, Guizhou Province, south-west PR China. Growth occurred at 15-40 °C (optimum, 30 °C), at pH 5.0-9.0 (optimum, pH 7.0-8.0) and with 0-1 % NaCl (w/v). The predominant respiration quinone was ubiquinone-10 (Q-10). The major cellular fatty acids were summed feature 8 (C18 : 1ω7c or C18 : 1ω6c; 83.9 %) and C16 : 0 (5.8 %). The major polar lipids were phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylcholine, phosphatidylglycerol, three unidentified phospholipids, two unidentified glycolipids, two unidentified polar lipids and one unidentified aminolipid. The DNA G+C content of strain Sn-9-2T was 67.5 mol%. Based on the results of 16S rRNA gene sequence analysis, the nearest phylogenetic neighbours of strain Sn-9-2T (MF958452) were identified as Aquabacter spiritensis (FR733686) DSM 9035T (97.5 %), Xanthobacter autorophicus (jgi.1053054) DSM 432T (97.2 %) and Xanthobacter tagetidis ATCC 700314T RCTF01000015 (96.9 %). The average nucleotide identity values were 78.0, 77.4 and 77.6 % and the digital DNA-DNA hybridization values were 21.8, 22.0 and 18.8 % between strain Sn-9-2T and A. spiritensis DSM 9035T, X. autotrophicus DSM 432T and X. tagetidis DSM 11105T, respectively. The DNA-DNA hybridization data indicated that strain Sn-9-2T represented a novel genomic species. On the basis of the results of phylogenetic analysis, chemotaxonomic data, physiological characteristics and DNA-DNA hybridization data, strain Sn-9-2T should represent a novel species of the genus Aquabacter, for which the name Aquabactercavernae sp. nov. is proposed. The type strain is Sn-9-2T (=KCTC 62308T=CCTCC AB 2018270T).

Antibacterial diketopiperazines from an endophytic fungus Bionectria sp. Y1085.

Two new diketopiperazines (1, 2), one new polyprenol (3), together with 19 known compounds (4-22) were obtained from the EtOAc extract of Bionectria sp. Y1085, an endophytic fungus isolated from the plant Huperzia serrata. Their structures were elucidated by extensive NMR and MS analysis. Bionectin D (1) is a rare diketopiperazine with a single methylthio substitution at the α-carbon of cyclized amino acid residue. The antibacterial activity of compounds was assayed against Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium ATCC 6539, and some metabolites (1, 2, 10, 11, and 14) exhibited evident antibacterial activity.

Flavisolibacter nicotianae sp. nov., isolated from rhizosphere soil of Nicotiana tabacum L.

A Gram-stain-negative, aerobic, non-motile and rod-shaped bacterium, designated strain X7XT, was isolated from a rhizosphere soil sample of Nicotiana tabacum L. collected from a tobacco factory located in Kunming, south-western China. The cells showed oxidase-positive and catalase-positive reactions. Growth occurred at 20-40 °C and pH 6.0-8.0, with optimal growth at 30 °C and pH 7.0. The predominant respiratory quinone was MK-7. The major fatty acids were identified as iso-C15 : 0, iso-C17 : 0 3OH and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c). The cellular polar lipids contained phosphatidylethanolamine, an unidentified aminophospholipid, two unidentified glycolipids, four unidentified aminolipids and four unidentified lipids. The genomic DNA G+C content was 49.7 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain X7XT should be affiliated to the genus Flavisolibacter. Results from further analysis showed that strain X7XT had highest 16S rRNA gene sequence similarity to Flavisolibacter metallilatus TX0661T (96.4 %) and 'Flavisolibacter swuensis' SR2-4-2T (96.4 %), followed by other species of the genus Flavisolibacter. The polyphasic taxonomic characteristics indicated that strain X7XT represents a novel species of the genus Flavisolibacter, for which the name Flavisolibacternicotianae sp. nov. (type strain X7XT=KCTC 62326T=CGMCC 16451T) is proposed.

Comparative Transcriptomics Reveals Features and Possible Mechanisms of Glucose-Mediated Soil Fungistasis Relief in Arthrobotrys oligospora.

Soil-borne pest diseases result in large annual agricultural losses globally. Fungal bio-control agents are an alternative means of controlling pest diseases; however, soil fungistasis limits the effect of fungal agents. Nutrients can relieve soil fungistasis, but the mechanisms behind this process remain poorly understood. In this study, we determined and quantified the transcriptomes of Arthrobotrys oligospora, a nematode-trapping fungus, derived from samples of fresh conidia, germinated conidia, soil fungistatic conidia, and glucose-relieved conidia. The transcriptomes of fungistatic and glucose-relieved conidia were significantly different from those of the other two conidia samples. KEGG pathway analyses showed that those genes upregulated in fungistatic and glucose-relieved conidia were mainly involved in translation and substance metabolism, and the downregulated genes were mainly involved in MAPK pathway, autophagy, mitophagy, and endocytosis. As being different from the transcriptome of fungistatic conidia, upregulated genes in the transcriptome of glucose-relieved conidia are also related to replication and repair, spliceosome, oxidative phosphorylation, autophagy, and degradation pathway (lysosome, proteasome, and RNA degradation). And the upregulated genes resulted from comparison of glucose-relieved conidia and fungistatic conidia were enriched in metabolic pathways, cycle, DNA replication, and repair. The differentially splicing events in the transcriptome of glucose-relieved conidia are far more than that of other two transcriptomes, and genes regulated by differentially splicing were analyzed through KEGG pathway analysis. Furthermore, autophagy genes were proved to play important role in resisting soil fungistasis and glucose-mediated soil fungistasis relief. These data indicate that, in addition to being a carbon and energy source for conidia germination, glucose may also help to relieve soil fungistasis by activating many cellular processes, including autophagy, DNA replication and repair, RNA alternative splicing, and degradation pathways.

Proteomic changes in Arthrobotrys oligospora conidia in response to benzaldehyde-induced fungistatic stress.

Soil fungistasis limits the effect of fungal agents designed to control plant-parasitic nematodes. Benzaldehyde is a fungistatic factor produced by soil microorganisms that can suppress conidial germination, but the molecular mechanism of this suppression is unknown. In this study, three conidial proteomes of Arthrobotrys oligospora ATCC24927, a nematode-trapping fungus, were obtained, quantified, and compared. Under benzaldehyde fungistatic stress, conidial protein expression profile changed significantly. Screening with a twofold selection criterion revealed 164 up-regulated and 110 down-regulated proteins. 17 proteins related to protein translation were down-regulated and gene transcription analysis suggested that the repression of proteins translation might be one mechanism by which benzaldehyde inhibites conidial germination. Benzaldehyde also resulted in the down-regulation of respiratory chain proteins and mitochondrial processes, as well as the repression of conidial DNA synthesis. In addition, the conidia up-regulated several proteins that enable it to resist benzaldehyde-induced fungistatis, and this was confirmed by a functional assessment of two knockout mutants. This study reveals putative mechanisms by which benzaldehyde causes fungistasis as well as the proteomic response of conidia to benzaldehyde. SIGNIFICANCE: Soil fungistasis limits the effect of fungal agents designed to control plant-parasitic nematodes. Benzaldehyde is one of fungistatic factors produced by soil microorganisms that can suppress conidial germination. In this study, we found that conidial protein expression profile changed significantly under benzaldehyde fungistatic stress. This research revealed new mechanistic data that describe how benzaldehyde is responsible for fungiststis by inhibiting conidial germination. Moreover, we also found that conidia can resist benzaldehyde by up-regulating proteins such as benzaldehyde dehydrogenase and heat shock proteins. This study also showed that proteomics methods play important roles in addressing soil fungistatic mechanisms.

Sphingomonas tabacisoli sp. nov., a member of the genus Sphingomonas, isolated from rhizosphere soil of Nicotiana tabacum L.

A Gram-staining-negative, aerobic, motile and rod-shaped bacterium, designated strain X1-8T, was isolated from rhizosphere soil of Nicotiana tabacum L. collected from the tobacco produce base located in Kunming, south-west PR China. Cells showed oxidase-negative and catalase-positive reactions and were motile by means of peritrichous flagella. Growth occurred at 25-40 °C and pH 6.0-8.0 with optimal growth at 30-35 °C, pH 7.0. The major respiratory lipoquinone was Q-10. C16 : 0 and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) were identified as major cellular fatty acids. The profile of polar lipids contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine, sphingoglycolipid, phosphatidylcholine and one unidentified glycolipid. The major polyamine was sym-homospermidine. The genomic DNA G+C content was 66.5 mol%. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that X1-8T should be affiliated to the genus Sphingomonasand formed a clade with most closely related species Sphingomonas changbaiensisNBRC 104936T. The results of 16S rRNA gene sequences similarity analysis indicated that X1-8T had the highest similarity with S. changbaiensisNBRC 104936T (98.4 %) and lower than 96.0 % with other species of the genus Sphingomonas. DNA-DNA hybridization data indicated that X1-8T represented a novel genomic species of the genus Sphingomonas. The characteristics determined in the polyphasic taxonomic study indicated that X1-8T represents a novel species of the genus Sphingomonas, for which the name Sphingomonas tabacisoli sp. nov. (type strain X1-8T=KCTC 62032T=CGMCC 1.16275T) is proposed.