[Effects of Combined Stress of High Density Polyethylene Microplastics and Chlorimuron-ethyl on Soybean Growth and Rhizosphere Bacterial Community].

With the vigorous development of agriculture in China， plastic mulch film and pesticides are widely used in agricultural production. However， the accumulation of microplastics （formed by the degradation of plastic mulch film） and pesticides in soil has also caused many environmental problems. At present， the environmental biological effects of microplastics or pesticides have been reported， but there are few studies on the combined effects on crop growth and the rhizosphere soil bacterial community. Therefore， in this study， the high density polyethylene microplastics （HDPE， 500 mesh） were designed to be co-treated with sulfonylurea herbicide chlorimuron-ethyl to study their effects on soybean growth. In addition， the effects of the combined stress of HDPE and chlorimuron-ethyl on soybean rhizosphere soil bacterial community diversity， structure composition， microbial community network， and soil function were investigated using high-throughput sequencing technology， interaction network， and PICRUSt2 function analysis to clarify the combined toxicity of HDPE and chlorimuron-ethyl to soybean. The results showed that the half-life of chlorimuron-ethyl in soil was prolonged by the 1% HDPE treatment （from 11.5 d to 14.3 d）， and the combined stress of HDPE and chlorimuron-ethyl had more obvious inhibition effects on soybean growth than that of the single pollutant or control. The HiSeq 2 500 sequencing showed that the rhizosphere bacterial community of soybean was composed of 20 phyla and 312 genera under combined stress， the number of phyla and genera was significantly less than that of the control and single pollutant treatment， and the relative abundances of bacteria with potential biological control and plant growth-promoting characteristics （such as Nocardioides and Sphingomonas） were reduced. Alpha diversity analysis showed that the combined stress significantly reduced the richness and diversity of the soybean rhizosphere bacterial community， and Beta diversity analysis showed that the combined stress significantly changed the structure of the bacterial community. The dominant flora of the rhizosphere bacterial community were regulated， and the abundances of secondary functional layers such as amino acid metabolism， energy metabolism， and lipid metabolism were reduced under combined stress by the analysis of LEfSe and PICRUSt2. It was inferred from the network analysis that the combined stress of HDPE and chlorimuron-ethyl reduced the total number of connections and network density of soil bacteria， simplified the network structure， and changed the important flora species to maintain the stability of the network. The results above indicated that the combined stress of HDPE and chlorimuron-ethyl significantly affected the growth of soybean and changed the rhizosphere bacterial community structure， soil function， and network structure. Compared with that of the single pollutant treatment， the potential risk of combined stress was greater. The results of this study can provide guidance for evaluating the ecological risks of polyethylene microplastics and chlorimuron-ethyl and for the remediation of contaminated soil.

Three new Dioszegia species (Bulleribasidiaceae, Tremellales) discovered in the phylloplane in China.

The genus Dioszegia is comprised of anamorphic basidiomycetous yeasts and is classified in the family Bulleribasidiaceae of the order Tremellales. Currently, 24 species have been described and accepted as members of the genus, although its diversity and global distribution have not been thoroughly investigated. In this study, yeasts were isolated from plant leaves collected in the Guizhou and Henan Provinces of China and identified through a combination of morphological and molecular methods. Phylogenetic analyses of the combined ITS and LSU sequences coupled with morphological studies revealed three novel species, D.guizhouensissp. nov., D.foliicolasp. nov., and D.aurantiasp. nov., proposed here. Additionally, our phylogenetic analyses suggest that the recently discovered species D.terrae is a synonym of D.maotaiensis. This study presents detailed descriptions and illustrations of three new Dioszegia species and highlights distinctions between them and their close relatives. The findings of this study contribute to our knowledge of the biodiversity of Dioszegia, offering a foundation for future research.

5-HT1A receptors within the intermediate lateral septum modulate stress vulnerability in male mice.

Chronic stress is a major risk factor for psychiatric disorders. However, certain individuals may be at higher risk due to greater stress susceptibility. Elucidating the neurobiology of stress resilience and susceptibility may facilitate the development of novel strategies to prevent and treat stress-related disorders such as depression. Mounting evidence suggests that the serotonin (5-HT) system is a major regulator of stress sensitivity. In this study, we assessed the functions of 5-HT1A and 5-HT2A receptors within the lateral septum (LS) in regulating stress vulnerability. Among a group of male mice exposed to chronic social defeat stress (CSDS), 47.2% were classified as stress-susceptible, and these mice employed more passive coping strategies during the defeat and exhibited more severe anxiety- and depression-like behaviors during the following behavioral tests. These stress-susceptible mice also exhibited elevated neuronal activity in the LS as evidenced by greater c-Fos expression, greater activity of 5-HT neurons in both the dorsal and median raphe nucleus, and downregulated expression of the 5-HT1A receptor in the intermediate LS (LSi). Finally, we found the stress-induced social withdrawal symptoms could be rapidly relieved by LSi administration of 8-OH-DPAT, a 5-HT1A receptor agonist. These results indicate that 5-HT1A receptors within the LSi play an important role in stress vulnerability in mice. Therefore, modulation of stress vulnerable via 5-HT1A receptor activation in the LSi is a potential strategy to treat stress-related psychiatric disorders.

Diversity of Wickerhamomyces (Wickerhamomycetaceae, Saccharomycetales) in China with the description of four new species.

Wickerhamomyces is a well-known genus of the family Wickerhamomycetaceae in the class Ascomycetes. These fungi can survive in a variety of substrates and environments and perform many valuable roles in both industrial processes and the natural ecosystems. During our investigation of yeast diversity associated with plant materials, 53 Wickerhamomyces isolates were obtained from rotting wood and plant leaves collected in Fujian, Guizhou, Henan, and Yunnan Provinces of China. Isolates were identified as 14 Wickerhamomyces species, including 1 species known previously to occur in China (W. anomalus), 9 new record species in China (W. arborarius, W. ciferrii, W. edaphicus, W. lynferdii, W. pijperi, W. subpelliculosa, W. xylosica, W. strasburgensis, and W. sydowiorum), and 4 novel species (W. guiyangensis sp. nov., W. paramyanmarensis sp. nov., W. quanzhouensis sp. nov., and W. phyllophilus sp. nov.). This study presents a detailed account of these new species, illustrating their morphology and analyzing their phylogenetic relationships with other Wickerhamomyces species. Our study is the first comprehensive study on Wickerhamomyces species associated with plant materials from tropical and subtropical China. The results of this study update our understanding of the phylogenetic relationships, systematics, and ecology of Wickerhamomyces.

Increased Lactobacillus Abundance Contributes to Stress Resilience in Mice Exposed to Chronic Social Defeat Stress.

INTRODUCTION: Accumulating evidence indicates that abnormalities in the composition of gastrointestinal (GI) microbiota play a vital role in stress-related disorders. Both human beings and animals perceive stressful events differently, i.e., resilience or susceptibility. However, the role of GI microbiota in stress resilience/susceptibility and the underlying mechanisms remain largely unknown. METHODS AND RESULTS: Sixty male C57BL/6J mice were exposed to 10-day chronic social defeat stress (CSDS), and 28 were found to be resilient to CSDS. We next analyzed microbiota compositions in the cecum using 16S rDNA gene sequencing, which revealed a significant increase in the relative abundance of Lactobacillus at the genus level in the resilient mice. In subsequent experiments, we found that oral administration of a strain of Lactobacillus (Lactobacillus murinus) for 2 weeks attenuated the increased levels of stress-induced corticosterone and anxiety-like behavior in stress-susceptible mice. The mRNA expression of tryptophan hydroxylase 2 (a rate-limiting enzyme in serotonin [5-HT] synthesis) was also significantly increased in the dorsal raphe nucleus (DR) of stress-susceptible mice. CONCLUSIONS: Lactobacillus contributes to stress resilience, and the DR 5-HT system may play an important role during this process. The above results suggest that certain organisms in the GI tract may play an essential role in stress response and be useful in the prevention and treatment of some stress-related psychiatric disorders, such as depression.

Yeast Diversity in the Qaidam Basin Desert in China with the Description of Five New Yeast Species.

The Qaidam Basin is the highest and one of the largest and driest deserts on Earth. It is considered a mars analog area in China. In contrast to numerous studies concerning its geology, geophysical, and chemistry, relatively few studies have reported microbial diversity and distribution in this area. Here, we investigated culturable yeast diversity in the northeast Qaidam Basin. A total of 194 yeast strains were isolated, and 12 genera and 21 species were identified, among which 19 were basidiomycetous yeasts. Naganishia albida, N. adeliensis, and Filobasidium magnum were the three most dominant species and were distributed in thirteen samples from eight locations. Five new species (Filobasidium chaidanensis, Kondoa globosum, Symmetrospora salmoneus, Teunia nitrariae, and Vishniacozyma pseudodimennae) were found and described based on ITS and D1D2 gene loci together with phenotypic characteristics and physiochemical analysis. Representative strains from each species were chosen for the salt-tolerant test, in which species showed different responses to different levels of NaCl concentrations. Further, the strain from soil can adapt well to the higher salt stress compared to those from plants or lichens. Our study represents the first report of the yeast diversity in the Qaidam Basin, including five new species, and also provides further information on the halotolerance of yeasts from the saline environment in mars analog.

The enhanced mechanisms of Hansschlegelia zhihuaiae S113 degrading bensulfuron-methyl in maize rhizosphere by three organic acids in root exudates.

The residues of bensulfuron-methyl (BSM), a sulfonylurea herbicide, in soil have caused serious damage to the rotation of susceptible crops. Many studies have reported that the removal of BSM in soil was achieved by adding degrading bacteria. However, the mechanisms used by bacteria to degrade BSM in the crop rhizosphere remain unclear. In this study, a BSM-degrading bacterium, Hansschlegelia zhihuaiae S113, was applied to investigate the enhancement of effects mediated by organic acids during the bioremediation of BSM-contaminated maize rhizosphere soil. Organic acids, such as L-malic acid, tartaric acid, and fumaric acid, identified in maize root exudates, significantly stimulated the expression of cheA, which encoded the histidine kinase in strain S113 and contributed to the chemotactic response. This process accelerated the accumulation of strain S113 around the maize roots and promoted the colonization process on maize roots. The growth of strain S113 was significantly increased by L-malic acid but not tartaric acid or fumaric acid. After the S113 suspension was root-irrigated to BSM-contaminated soil, the density of strain S113 colonizing root surfaces and in rhizosphere soil reached 1.1 × 104 cells/g for roots and 4.9 × 104 cells/g in dry soil at 15 d, leading to 80.9% BSM degradation efficiency. The treatment with the addition of a mixture of S113 and L-malic acid completely degraded BSM in rhizosphere soil due to the strong attraction and growth promotion of strain S113 by L-malic acid, with a higher efficiency than that with the extra addition of fumaric acid (89.7%) or tartaric acid (87.0%). This paper revealed the enhancement effects of organic acids identified in root exudates for the in situ bioremediation of BSM-contaminated rhizosphere soil.

The Prevention of Bio-Organic Fertilizer Fermented from Cow Manure Compost by Bacillus sp. XG-1 on Watermelon Continuous Cropping Barrier.

The continuous cropping barrier is an important factor leading to the decline of watermelon quality and yield. In this study, we focused on a bio-organic fertilizer prepared with one bacterial strain, Bacillus sp. XG-1, to prevent the occurrence of the continuous cropping barrier. The strain XG-1 was isolated from watermelon rhizosphere soil, and promoted the growth of watermelon by producing phytase (0.19 U/mL), indole-3-acetic acid (IAA, 7.31 mg/L), and gibberellins (GA3, 2.47 mg/L). In addition, the strain also possessed a strong antagonistic effect against the pathogen Fusarium oxysporum f. sp. niveum (Fon) by inhibiting conidia germination with an inhibition ratio of 85.3% and mycelium growth. The bio-organic fertilizer fermented by XG-1, based on cow manure compost and rapeseed meal (85:15, w/w) under optimal conditions, was mixed in soil (watermelon had been planted for two consecutive years). After the cultivation of watermelon for 50 d, a higher density of XG-1 (9.79 × 105 colony-forming units (CFU)/g) and one order of magnitude lower of Fon (1.29 × 103 copies/g) were detected in the rhizosphere soil compared with soils without bio-organic fertilizer (7.59 × 104 copies/g for Fon), leading to an 86.4% control efficiency of watermelon caused by Fusarium wilt. The application of bio-organic fertilizer enriched soil nutrients, including the organic matter (13.2%), total nitrogen (13.9%), total phosphorus (20.5%), and total potassium (3.77%), adjusted the soil pH from 6.69 to 7.01, and significantly improved the watermelon growth in terms of the seedling height, root length, fresh weight of seedling and root with increase of 78.8%, 72.2%, 84.6%, and 96.4%, respectively. This study regarded the watermelon continuous cropping soil as the research point, and focused on inhibiting Fon, regulating soil properties and enhancing watermelon growth to eliminate the continuous cropping barrier through a combination of compost and functional strains, demonstrating the potential application value in watermelon production.

Metschnikowia henanensis sp. nov., a new anamorphic yeast species isolated from rotten wood in China.

Four yeast strains were isolated from rotting wood samples collected from two sites in the Baotianman Nature Reserve and the Laojieling Nature Reserve in China. DNA sequence comparison and other taxonomic characteristics identified the strains as a single novel species of the genus Metschnikowia. The name Metschnikowia henanensis sp. nov. is proposed to accommodate these highly divergent organisms with the type strain BY-97(T) (= CICC 1982(T) = CBS 12677(T)). The novel species produced chlamydospores, but it did not exhibit ascospore formation in sporulation media for 4 weeks. Molecular phylogeny from the D1/D2 domains of the large subunit (LSU) rRNA gene sequences placed this new species in a basal position to the Metschnikowia viticola/Candida kofuensis/Metschnikowia noctiluminum subclade, and an undescribed Candida species namely strains IMB-EMP4 and IMB-EMP5 was a close sister to M. henanensis.

Candida sanyaensis sp. nov., an ascomycetous yeast species isolated from soil.

Strains representing a novel ascomycetous yeast species, Candida sanyaensis, were isolated from soil samples collected on Hainan Island and Taiwan Island in China. Analysis of the D1/D2 domains of the large subunit (LUS) rRNA gene and internal transcribed spacer (ITS) regions of these strains showed that this species was related to Candida tropicalis and Candida sojae, their closest relatives. C. sanyaensis differed by three substitutions and one gap from C. tropicalis, and by four substitutions and one gap from C. sojae, in the D1/D2 domain sequences. However, the ITS sequences of C. sanyaensis were quite divergent from the latter two species, showing that it is a genetically separate species. The novel strains were also found to have very similar PCR-fingerprinting profiles which were quite distinct from those of C. tropicalis and C. sojae strains. The type strain of C. sanyaensis is HN-26(T) (= CICC 1979(T) = CBS 12637(T)).

Wickerhamomyces mori sp. nov., an anamorphic yeast species found in the guts of wood-boring insect larvae.

A novel anamorphic yeast species is described to accommodate three isolates recovered from the guts of three different wood-boring insect larvae collected in Henan, central China. On the basis of sequence analyses of the D1/D2 domains of the large-subunit rRNA gene and the internal transcribed spacer regions, the three strains are assigned to a novel species of the genus Wickerhamomyces, although the formation of ascospores was not observed. These strains also exhibited a number of distinct morphological and physiological characteristics that clearly differentiated them from Wickerhamomyces mucosus, Candida odintsovae and Wickerhamomyces rabaulensis, the most closely related species. In view of the phenotypic differences and unique rRNA gene sequences, we consider that these three isolates represent a novel species of the genus Wickerhamomyces, Wickerhamomyces mori sp. nov. The type strain is NYNU 1216(T) ( = CICC 1983(T)  = CBS 12678(T)).

Colonization of Caenorhabditis elegans by Bacillus nematocida B16, a bacterial opportunistic pathogen.

BACKGROUND: Soil-dwelling Bacillus nematocida B16 can kill Caenorhabditis elegans via a Trojan horse-like mechanism. However, colonization is a key problem that must be solved during the infection process. AIMS: To study the molecular mechanism involved in the colonization of B. nematocida B16 against the host C. elegans. METHODS: GFP-expressing strain B16g was constructed and its nematocidal activity was assayed. 'Feeding transfer' experiments were carried out separately using of B16 and B16g strains to explore the colonization mode of the bacteria. Fluorescence microscopy was used to observe the interactions between fluorescent signal and the quantity of bacteria in the intestine. A mariner-based transposon called TnYLB-1 was also applied in the random mutagenesis of B16 to screen the mutants with impaired colonization of nematode worms and identify potential localization-related genes. RESULTS AND CONCLUSION: A small inoculum of the bacteria resulted in its proliferation in the C. elegans intestine. The fluorescence signal was enhanced with increasing bacterial density in the intestine. Several candidate genes with possibly important roles in colonization were found. These results provide a solid foundation for further elucidation of the infection process at the molecular level and enrichment of our knowledge of bacterial pathogenesis.

Cryptococcus nanyangensis sp. nov., a new basidiomycetous yeast isolated from the gut of wood-boring larvae.

Two strains of a novel basidiomycetous yeast species were isolated from the gut of wood-boring larvae collected in the Baotianman Nature Reserve, the central China. Sequence analysis of the D1/D2 domains of the large subunit (LSU) rRNA gene and internal transcribed spacer (ITS) regions showed that these yeasts belong to the Bulleromyces clade and formed a cluster together with eleven undescribed Cryptococcus species. The novel species differed from its closest known species, Cryptococcus rajasthanensis, by 3.3 % divergence (15 substitutions and 6 gaps over 630 bases) in the D1/D2 domains, and by 13.4 % divergence (41 substitutions and 27 gaps over 508 bases) in the ITS regions. Physiologically, the fermentation of glucose, galactose, sucrose, trehalose, and raffinose in Durham tubes was observed for the strains of this new yeast. Based on the phenotypical and molecular characteristics presented, the two strains are proposed as a new species, Cryptococcus nanyangensis sp. nov., with the type strain KCY-1(T) (=CICC 1976(T) = CBS 12474(T)).

Candida ficus sp. nov., a novel yeast species from the gut of Apriona germari larvae.

A novel yeast species is described based on three strains from the gut of wood-boring larvae collected in a tree trunk of Ficus carica cultivated in parks near Nanyang, central China. Phylogenetic analysis based on sequences of the D1/D2 domains of the large subunit rRNA gene showed that these strains occurred in a separate clade that was genetically distinct from all known ascomycetous yeasts. In terms of pairwise sequence divergence, the novel strains differed by 15.3% divergence from the type strain of Pichia terricola, and by 15.8% divergence from the type strains of Pichia exigua and Candida rugopelliculosa in the D1/D2 domains. All three are ascomycetous yeasts in the Pichia clade. Unlike P. terricola, P. exigua and C. rugopelliculosa, the novel isolates did not ferment glucose. The name Candida ficus sp. nov. is proposed to accommodate these highly divergent organisms, with STN-8(T) (=CICC 1980(T)=CBS 12638(T)) as the type strain.

Bacillus nematocida sp. nov., a novel bacterial strain with nematotoxic activity isolated from soil in Yunnan, China.

An endospore-forming bacterium, designated strain B-16T, was isolated from a forest soil sample in Yunnan, China. The isolate presented remarkable nematotoxic activity against nematode Panagrellus redivivus. The organism was strictly aerobic, motile, spore forming and rod shaped, catalase- and oxidase-positive. The predominant isoprenoid quinone was menaquinone 7 (MK-7). The major cellular fatty acid profiles were anteiso-C15:0 (48.67%), iso-C15:0 (13.45%), C16:0 (9.06%) and anteiso-Cl7:0 (8.29%). The DNA G+C content was 46%. Phylogenetic analyses based on 16S rDNA sequence revealed that isolate belongs to the genus Bacillus. Strain B-16T exhibited high 16S rDNA similarity with its closest neighbors Bacillus vallismortis (99.79%), B. subtilis (99.43%), B. atrophaeus (99.43%), B. amyloliquefaciens (99.36%), B. licheniformis (98.0%) and less than 97.0% with all the other relative type strains in the genus Bacillus. The phenotypic and genotypic characteristics and DNA-DNA relatedness data indicate that strain B-16T should be distinguished from all the relative species of genus Bacillus. Therefore, on the basis of the polyphasic taxonomic data presented, a new species of the genus Bacillus, B. nematocida, with the type strain B-16T ( = CGMCC 1128T) is proposed. The GenBank accession number for the sequence reported in this paper is AY820954.