Isolation and Identification of Culturable Bacteria from South China Seawater and Preliminary Screening of Marine Biocontrol Bacteria.

Marine microorganisms have evolved special metabolic pathways to produce numerous bioactive substances with novel structures and unique functions. This study analyzed the diversity of culturable bacteria in marine water samples from the South China Sea and screened the isolated bacteria with pathogenic fungi. A total of 200 culturable strains of 72 different bacteria were obtained from 56 water samples from the South China Sea. They belonged to three phyla and four classes, namely Gammaproteobacteria, Alphaproteobacteria, Bacilli and Actinomycetia. Bacilli was the dominant class, comprising up to 59.72%, followed by Gammaproteobacteria (20.83%). Bacillus, Pseudomonas, Paenibacillus and Rhizobium were the most dominant genera. Among these strains, HY-88 and HY-91 encoding BamC, FenB and PKSI genes were selected and identified as Bacillus subtilis. The respective inhibition rates of the HY-88 caused by plate confrontation against Magnaporthe grisea, Fusarium oxysporum, Botrytis cinerea, anthrax and Botrytis cinerea were 90.91%, 54.29%, 52.17% and 51.72%, in comparison with HY-91 86.36%, 48.57%, 47.83% and 34.48%. In addition, the supernatant of HY-88 showed a lesion inhibition rate of 74.5%, which was significantly higher than HY-91 (60.55%). In addition, HY-88 and HY-91 showed strong antifungal activity to Colletotrichum viniferum on detached Shine Muscat grapes. Tolerance tests showed that the HY-88 and HY-91 grew at 10-40 °C, 7-10% NaCl and pH 3-11. HY-88 and HY-91 could inhibit various fungal plant diseases, which lays a foundation for the development of new biopesticides.

Glucose Oxidase of a Crucifer-Specialized Insect: A Potential Role in Suppressing Plant Defense via Modulating Antagonistic Plant Hormones.

Glucose oxidase (GOX) is a representative compound found in most insect saliva that can suppress plant-defensive responses. However, little is known about the origin and role of GOX in the crucifer-specialized pest Plutella xylostella. In this study, we showed obvious regurgitation from the larval gut of P. xylostella and identified abundant peptides highly similar to known GOX. Three PxGOX genes were verified with PxGOX2 preferentially expressed in the gut. The heterologously expressed PxGOX2 confirmed its function to be a GOX, and it was detected in plant wounds together with the gut regurgitant. Further experiments revealed that PxGOX2 functioned as an effector and may suppress defensive responses in plant through the production of H2O2, which modulates levels of antagonistic salicylic acid and jasmonic acid. However, excessive H2O2 in the host plant may be neutralized by peroxidase, thus forming defensive feedback. Our findings provided new insights into understanding the GOX-mediated insect-plant interactions.

Talaromyces sp. Ethyl Acetate Crude Extract as Potential Mosquitocide to Control Culex pipiens quinquefasciatus.

Vector control is considered an effective approach to controlling diseases spread by mosquito bites. Entomopathogenic fungi are widely used in agriculture to control insect pests, and fungal metabolites can potentially be developed as effective mosquitocides. In this study, a high-throughput screening method was used to search for potential mosquitocides in the Global Fungal Extract Library (GFEL). We tested the larvicidal activity of 264 fungal ethyl acetate crude extracts against Culex pipiens quinquefasciatus. Nine fungal extracts caused moderate to high mortality rates (>50%), with two fungal extracts (58A7 and 101H12) causing a 100% mortality rate. The lethal concentrations for 50% of the population (LC50) were 44.27 mg/L and 31.90 mg/L, respectively. Fraction 14 had a high mortality rate, with an LC50 value of 12.13 mg/L, and was isolated from 58A7 (Fractions 1-11) and 101H12 (Fractions 12-15). Further analyses showed that Fraction 14 was made up of vermistatin and dihydrovermistatin. In a Cx. p. quinquefasciatus larvicidal bioassay, vermistatin (LC50 = 28.13 mg/L) was more toxic than dihydrovermistatin (LC50 = 83.87 mg/L). Our findings suggested that the active fungal extract 101H12 from Talaromyces sp. and its compound vermistatin could be developed as mosquitocides.

Removal of low-concentration tetracycline from water by a two-step process of adsorption enrichment and photocatalytic regeneration.

Developing a high-performance method that can effectively control pollution caused by low concentrations of antibiotics is urgently needed. Herein, a novel three-dimensional PPy/Zn3In2S6 nanoflower composites were prepared for the comprehensive treatment of low-concentration tetracycline (Tc) hydrochloride in wastewater based on the adsorption/photocatalysis of Zn3In2S6 and the conductivity of PPy. In this preparation method, adsorption enrichment and photocatalytic regeneration were conducted in two steps, eliminating the dilution and dispersion effects of aqueous solvents on photocatalytic species and antibiotics. Results showed that Zn3In2S6 could effectively adsorb 87.85% of Tc at pH of 4.5 and photocatalytically degrade Tc at pH of 10.5. Although the adsorption capacity of Zn3In2S6 was slightly reduced after being combined with PPy, its photocatalytic efficiency was substantially enhanced. Specifically, 0.5%PPy/Zn3In2S6 could degrade 99.92% of the surface-enriched Tc in 1 h and induce the regeneration of the adsorption sites. Furthermore, the adsorption capacity remained above 85% even after recycling PPy/Zn3In2S6 ten times. The photocatalytic degradation mechanism analysis revealed that the enrichment of Tc on 0.5%PPy/Zn3In2S6 negatively impacts the photocatalytic efficiency, while •O2- and •OH radicals were the main oxidative species that played an important role in the photoregeneration process.

Landscape Composition and Soil Physical-Chemical Properties Drive the Assemblages of Bacteria and Fungi in Conventional Vegetable Fields.

The soil microbiome is crucial for improving the services and functioning of agroecosystems. Numerous studies have demonstrated the potential of soil physical-chemical properties in driving the belowground microbial assemblages in different agroecosystems. However, not much is known about the assemblage of bacteria and fungi in response to soil physical-chemical properties and the surrounding landscape composition in different vegetable fields of a highly intensive agricultural system. Here, we investigated the effects of soil physical-chemical properties and landscape composition on the community trends of bacteria and fungi in two different soil compartments (bulk and rhizospheric soils) of two different brassica crop types (Chinese cabbage and flower cabbage). The results revealed that bulk soil had a higher alpha diversity of both bacteria and fungi than rhizospheric soil. Each of the soil physical-chemical properties and landscape compositions contributed differently to driving the community structure of distinct bacterial and fungal taxa in both soil compartments and crop types. The higher proportions of forest, grassland, and cultivated land, along with the higher amount of soil calcium in flower cabbage fields, promote the assemblage of Gammaproteobacteria, Actinobacteria, Oxyophotobacteria, Agaricomycetes, and Eurotiomycetes. On the other hand, in Chinese cabbage fields, the increased amounts of iron, zinc, and manganese in the soil together with higher proportions of non-brassica crops in the surrounding landscape strongly support the assemblage of Deltaproteobacteria, Gemmatimonadetes, Bacilli, Clostridia, Alphaproteobacteria, an unknown bacterial species Subgroup-6, Mortierellomycetes, Rhizophlyctidomycetes, and Chytridiomycetes. The findings of this study provide the most comprehensive, comparative, and novel insights related to the bacterial and fungal responses in a highly intensive vegetable growing system for the improvement of the soil fertility and structure. These are important clues for the identification of key bacteria and fungi contributing to the plant-environment interactions and are of a practical significance for landscape-based ecological pest management.

Cyclic enrichment of chromium based on valence state transformation in metal-free photocatalytic reductive imprinted composite hydrogel.

Cr (VI) exists in anion form and can be reduced to positive charged Cr (III) under certain conditions. Can positive charged Cr (III) be continually used for absorbing Cr (VI) to achieve cyclic accumulation of chromium? In this paper, an ion imprinting material for adsorption of Cr (VI) was prepared by dispersing polypyrrole (PPy) in a gelatin/chitosan (Gel/CS) hydrogel network, named Gel/CS/PPy. Based on the conversion of Cr (VI) to Cr (III), a cyclic enrichment process including adsorption-photoreduction-fixation-readsorption of Cr (VI) was established in Gel/CS/PPy hydrogel. The composition and structure of the Gel/CS/PPy were analyzed by scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric (TGA), texture analyzer (Universal TA), zeta potential and ultraviolet-visible-near infrared spectra (UV-vis-NIR). The conversion of Cr (VI) and Cr (III) and its promoting effect on readsorption were verified by XPS. The results showed that Gel/CS/PPy has good adsorption capacity for Cr (VI) and excellent photocatalytic ability to reduce Cr (VI) to Cr (III). Cr (III)-loaded Gel/CS/PPy can be further used to adsorb Cr (VI) and showed good adsorption efficiency even after four cycles. The optimal operating condition for Cr (VI) adsorption is pH = 3; 2 g/L dose of Gel/CS/PPy; and the adsorption capacity of Cr (VI) was about 106.8 mg/g after six adsorption cycles. Since Gel/CS/PPy is composed of organic components, high purity chromium can be recovered by simple calcination method later. Therefore, the synthesized Gel/CS/PPy has great potential in the practical application of low concentration Cr (VI) treatment in water.

Fitness comparison of Plutella xylostella on original and marginal hosts using age-stage, two-sex life tables.

The diamondback moth, Plutella xylostella, is an important agricultural pest that severely damages cruciferous vegetables. Although previously considered a threat only to Brassica species, P. xylostella has been observed to feed on noncruciferous vegetables. Here, we established a population of P. xylostella on the pea Pisum sativum (PxP population). We compared this PxP population's performance on the pea host plant to a population (PxR) reared on the original host plant radish (Raphanus sativus) for several generations using an age-stage, two-sex life table and analyzed the correlations between different fitness parameters. In the 1st generation of the PxP population, survival rate of immature stage was 17%, while the survival rate of PxR was 68%; the duration of the 4th larval instar (5.30 d) and mortality (25%) of this generation were significantly longer (2.8 d) and higher (1%) than that of PxR, respectively (both p < .001). Upon long-term acclimation, the PxP fitness improved significantly, especially that the survival rate of immature stages increased to approximately 60% in the 15th, 30th, and 45th generations. However, PxP feeding on pea exhibited poorer fitness with longer larval developmental time, shorter total life span, lighter pupa, and lower fecundity in different generations compared with PxP feeding on radish. PxP feeding on pea also showed a significantly lower intrinsic rate of increase (r), net reproduction rate (R 0), finite increase rate (λ), and longer mean generation time (T) than PxP feeding on radish in all generations tested. Significant positive correlations were observed between pupal weight and female fecundity in pea-fed populations, and between female longevity and female fecundity in pea-fed and radish-fed populations. Our findings suggest that P. xylostella adaptation to pea does not improve overall fitness compared with the original host radish, making pea a marginal host for P. xylostella.

Differential Profiles of Gut Microbiota and Metabolites Associated with Host Shift of Plutella xylostella.

Evolutionary and ecological forces are important factors that shape gut microbial profiles in hosts, which can help insects adapt to different environments through modulating their metabolites. However, little is known about how gut microbes and metabolites are altered when lepidopteran pest species switch hosts. In the present study, using 16S-rDNA sequencing and mass spectrometry-based metabolomics, we analyzed the gut microbiota and metabolites of three populations of Plutella xylostella: one feeding on radish (PxR) and two feeding on peas (PxP; with PxP-1 and PxP-17 being the first and 17th generations after host shift from radish to peas, respectively). We found that the diversity of gut microbes in PxP-17 was significantly lower than those in PxR and PxP-1, which indicates a distinct change in gut microbiota after host shift. Kyoto Encyclopedia of Genes and Genomes analysis revealed that the functions of energy metabolism, signal transduction, and xenobiotics biodegradation and metabolism were increased in PxP-17, suggesting their potential roles in host adaptation. Metabolic profiling showed a significant difference in the abundance of gut metabolites between PxR and PxP-17, and significant correlations of gut bacteria with gut metabolites. These findings shed light on the interaction among plants, herbivores, and symbionts, and advance our understanding of host adaptation associated with gut bacteria and metabolic activities in P. xylostella.

Fungal Endophyte Communities of Crucifer Crops Are Seasonally Dynamic and Structured by Plant Identity, Plant Tissue and Environmental Factors.

Endophytic fungi are important in diverse plant functions but knowledge of the factors that shape assemblages of these symbionts is lacking. Here, using a culture-dependent approach, we report 4,178 endophytic fungal isolates representing 16 orders isolated from stems, roots and leaves of three cruciferous plant species, Chinese cabbage (Brassica rapa L.), radish (Raphanus sativus L.) and white cabbage (B. olerocea L.), collected from 21 focal fields with different landscape contexts and pesticide uses during four seasons (summer, autumn, winter and spring). The colonization rate of fungi was found to be most strongly affected by season, plant identity and plant tissue. The colonization was highest during autumn, followed by summer, spring and lowest during winter. The colonization was highest in B. olerocea (53.2%), followed by B. rapa (42.6%), and lowest in R. sativus (35.0%). The colonization was highest in stems (51.9%) in all plant types, followed by leaves (42.4%) and roots (37.5%). Hypocreales was the dominant order (33.3% of all the isolates), followed by Glomerellales (26.5%), Eurotiales (12.1%), Pleosporales (9.8%) and Capnodiales (6.0%). Fungal endophyte abundance (number of isolates) followed the same pattern as colonization rate, while species richness varied with season and host plant tissue. Ordination analyses showed that the abundance and richness of Hypocreales, Eurotiales and Sordariales were associated with plant roots, while Capnodiales, Pleosporales and Trichosphaeriales were associated with spring. Other environmental factors, elevation, and the proportions of grassland, forest, orchard and waterbodies in the surrounding landscape also exerted effects within some categories of other main effects or for certain fungal taxa. Our results indicate that while fungal endophyte communities of crucifer crops vary strongly with the season, they are also strongly structured by plant identity and plant tissue, to a lesser extent by pesticide use and only weakly by landscape composition. The understanding of the ecological roles of fungal endophytes could contribute to habitat management and consequently improve crop pest management.

Mass spectrometry imaging: An emerging technology for the analysis of metabolites in insects.

Mass spectrometry imaging (MSI) can visualize the composition, abundance, and spatial distribution of molecules in tissues or cells, which has been widely used in the research of life science. Insects, especially the agricultural pests, have received a great deal of interests from the scientists in biodiversity and food security. This review introduces the major characteristics of MSI, summarizes its application to the investigation of insect endogenous metabolites, exogenous metabolites, and the spatiotemporal changes of metabolites between insects and plants, and discusses its shortfalls and perspectives. The significance of these concerns is beneficial for future insect research such as physiology and metabolism.

Host Plant-Derived miRNAs Potentially Modulate the Development of a Cosmopolitan Insect Pest, Plutella xylostella.

Plant microRNAs (miRNAs) have recently been reported to be involved in the cross-kingdom regulation of specific cellular and physiological processes in animals. However, little of this phenomenon is known for the communication between host plant and insect herbivore. In this study, the plant-derived miRNAs in the hemolymph of a cruciferous specialist Plutella xylostella were identified by small RNAs sequencing. A total of 39 miRNAs with typical characteristics of plant miRNAs were detected, of which 24 had read counts ≥ 2 in each library. Three plant-derived miRNAs with the highest read counts were validated, and all of them were predicted to target the hemocyanin domains-containing genes of P. xylostella. The luciferase assays in the Drosophila S2 cell demonstrated that miR159a and novel-7703-5p could target BJHSP1 and PPO2 respectively, possibly in an incomplete complementary pairing mode. We further found that treatment with agomir-7703-5p significantly influenced the pupal development and egg-hatching rate when reared on the artificial diet. The developments of both pupae and adults were severely affected upon their transfer to Arabidopsis thaliana, but this might be independent of the cross-kingdom regulation of the three plant-derived miRNAs on their target genes in P. xylostella, based on expression analysis. Taken together, our work reveals that the plant-derived miRNAs could break the barrier of the insect mid-gut to enter the circulatory system, and potentially regulate the development of P. xylostella. Our findings provide new insights into the co-evolution of insect herbivore and host plant, and novel direction for pest control using plant-derived miRNAs.

Genetic control of Plutella xylostella in omics era.

Diamondback moth, Plutella xylostella (L.), is a specialist pest on cruciferous crops of economic importance. The large-scale use of chemical insecticides for the control of this insect pest has caused a number of challenges to agro-ecosystems. With the advent of the omics era, genetic pest management strategies are becoming increasingly feasible and show a powerful potential for pest control. Here, we review strategies for using transgenic plants and sterile insect techniques for genetic pest management and introduce the major advances in the control of P. xylostella using a female-specific RIDL (release of insects carrying a dominant lethal gene) strategy. Further, the advantages of gene drive developed in combination with sex determination and CRISPR/Cas9 systems are addressed, and the corresponding prospects and implementation issues are discussed. It is predictable that under the policy and regulation of professional committees, the genetic pest control strategy, especially for gene drive, will open a new avenue to sustainable pest management not only for P. xylostella but also for other insect pests.

The roles of IL-6, IL-8 and IL-10 gene polymorphisms in gastric cancer: A meta-analysis.

BACKGROUND: Recently, the roles of interleukin-6 (IL-6), IL-8 and IL-10 gene polymorphisms in gastric cancer have been extensively studied, with conflicting results. Therefore, we conducted the present study to better assess the potential correlations between these interleukin gene polymorphisms and gastric cancer. METHODS: Eligible articles were searched in PubMed, Medline, Embase, Web of Science and CNKI. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to detect any potential associations between interleukin gene polymorphisms and the risk of gastric cancer. RESULTS: A total of 73 case-control studies were finally included. Significant associations with the risk of gastric cancer were only detected for the IL-8 rs4073 polymorphism in overall analyses. Further subgroup analyses according to ethnicity of participants revealed that the IL-6 rs1800796, IL-8 rs4073, IL-10 rs1800871, IL-10 rs1800872 and IL-10 rs1800896 polymorphisms were all significantly associated with the risk of gastric cancer in Asians. No positive results were found for any investigated interleukin gene polymorphisms in Caucasians. CONCLUSIONS: Our findings suggest that IL-6 rs1800796, IL-8 rs4073, IL-10 rs1800871, IL-10 rs1800872 and IL-10 rs1800896 polymorphisms may serve as genetic biomarkers of gastric cancer in Asians.