Colonization Ability Research Articles

Interplay between Arabidopsis thaliana Genotype, Plant Growth and Rhizosphere Colonization by Phytobeneficial Phenazine-Producing Pseudomonas chlororaphis.

Rhizosphere colonization by phytobeneficial Pseudomonas spp. is pivotal in triggering their positive effects on plant health. Many Pseudomonas spp. Determinants, involved in rhizosphere colonization, have already been deciphered. However, few studies have explored the role played by specific plant genes in rhizosphere colonization by these bacteria. Using isogenic Arabidopsis thaliana mutants, we studied the effect of 20 distinct plant genes on rhizosphere colonization by two phenazine-producing P. chlororaphis strains of biocontrol interest, differing in their colonization abilities: DTR133, a strong rhizosphere colonizer and ToZa7, which displays lower rhizocompetence. The investigated plant mutations were related to root exudation, immunity, and root system architecture. Mutations in smb and shv3, both involved in root architecture, were shown to positively affect rhizosphere colonization by ToZa7, but not DTR133. While these strains were not promoting plant growth in wild-type plants, increased plant biomass was measured in inoculated plants lacking fez, wrky70, cbp60g, pft1 and rlp30, genes mostly involved in plant immunity. These results point to an interplay between plant genotype, plant growth and rhizosphere colonization by phytobeneficial Pseudomonas spp. Some of the studied genes could become targets for plant breeding programs to improve plant-beneficial Pseudomonas rhizocompetence and biocontrol efficiency in the field.

The use of Caenorhabditis elegans model to screen lactobacilli for the control of patulin

Patulin, a type of mycotoxin, presents a serious threat to human and animal health. Lactic acid bacteria (LAB) have been shown to effectively detoxify patulin and have strong application prospects in this regard. However, the efficient selection of LAB with patulin detoxification, especially in vivo, requires costly animal experiments. The nematode Caenorhabditis elegans is an ideal model for the prescreening of probiotics and for toxicity evaluation studies. In the present study, 15 LAB isolates were evaluated for their protection of C. elegans against patulin exposure, and only three strains—Lacticaseibacillus casei ZM4, Lactobacillus johnsonii PC4, and Lactiplantibacillus plantarum subsp. plantarum M2—conferred protection at rates of 5.71%, 2.86%, and 48.57% on the eighth day, respectively. The capacities of these three strains for patulin binding, reduction of C. elegans reproduction toxicity, C. elegans colonization, and C. elegans immune regulation were further evaluated. These three strains showed similar patulin binding abilities at about 30%, while Lactiplantibacillus plantarum subsp. plantarum M2 showed better C. elegans reproduction toxicity detoxification. In addition, only Lactiplantibacillus plantarum subsp. plantarum M2 revealed the ability of colonization in C. elegans and immune regulation. Lactiplantibacillus plantarum subsp. plantarum M2 significantly upregulated the DAF/IGF pathway gene daf-16 and the antitoxin genes sod-3, spp-1 and lys-7, while mutants that were defective in daf-16 or sod-3 showed no response to protection from Lactiplantibacillus plantarum subsp. plantarum M2. These results suggest that C. elegans can be used to efficiently screen for patulin detoxification strains and the selected strain Lactiplantibacillus plantarum subsp. plantarum M2 shows both patulin binding and C. elegans immune regulation via the DAF/IGF pathway to control the production of superoxide dismutase to combat patulin exposure.

Vibrio splendidus virulence to Apostichopus japonicus is mediated by hppD through glutamate metabolism and flagellum assembly

ABSTRACT Vibrio splendidus is the main opportunistic pathogen that causes skin ulcer syndrome in Apostichopus japonicus. hppDIn the present study, mutant V. splendidus with an in-frame deletion of hppDV.s. (MTVs) was constructed. The median lethal doses of wild-type V. splendidus (WTVs) and MTVs were 5.129 × 106 and 2.606 × 1010 CFU mL−1, respectively. RNA-Seq was performed using WTVs and MTVs cells at different growth stages to explore the mechanisms of the pathogenesis mediated by hppDV.s. Gene Ontology analysis showed that the expression levels of 105 genes involved in amino acid metabolism and protein binding were remarkably different between MTVs and WTVs. Kyoto Encyclopedia of Genes and Genomes analysis showed that the pathways of glutamate metabolism and flagellum assembly involved in biofilm formation and swarming motility were suppressed in MTVs. Correspondingly, the swarming motility, biofilm formation and colonisation of MTVs were remarkably decreased compared with those of WTVs. The results showed that 4-hppD catalyses tyrosine into fumarate, which could enhance glutamate metabolism and ATP production; promote flagellum assembly through the TCA cycle and lead to higher swarming, biofilm formation and colonisation abilities, to contribute to the pathogenesis of V. splendidus.

Decoding the potential of a new Pseudomonas putida strain for inducing drought tolerance of tomato (Solanum lycopersicum) plants through seed biopriming

A total of 11 potential plant growth promoting rhizobacteria previously isolated from naturally stressed environments were evaluated for various traits of interest for a beneficial symbiosis with plants, including colonization ability, biofilm formation, motility, exopolysaccharide production and salt tolerance. The vast majority of the strains were found to possess multiple plant growth promoting traits. Nevertheless, the intensity varied among isolates, with those originated from tomato plants being more efficient colonizers. The strain SAESo11, genetically characterized as a Pseudomonas putida member was selected for further investigation of its potential to alleviate drought stress in tomato seedlings. Inoculation with SAESo11 mitigated the negative effects of drought stress as indicated by growth and photosynthetic indices. Furthermore, bacterial inoculation enhanced H2O2 content and malondialdehyde levels in colonized plants. Drought treatment did not further alter the oxidative status of these plants. Similarly, total phenolic content and antioxidant enzyme activity were induced in plant tissues in response to drought stress only at the absence of inoculum. These results indicated that inoculation with the selected strain imposed plants at a priming state, that enabled them to respond more robustly at the exposure to drought stress and efficiently attenuated the drought-induced injury. This state of plant alertness mediated by SAESo11 occurred at no cost to growth, highlighting its role as a potential plant priming agent.

Effects of duck circovirus on immune function and secondary infection of Avian Pathogenic Escherichia coli

Duck circovirus (DuCV) infection occurs frequently in ducks in China and is generally believed to lead to immunosuppression and secondary infection, though there has been a lack of detailed research and direct evidence. In this study, one-day-old Cherry Valley ducklings were artificially infected with DuCV alone and co-infected with DuCV and Avian Pathogenic Escherichia coli (APEC). The immune indexes at 32 d old were systematically monitored, including immune organ weight, lymphocyte transformation rate, IL-10, IL-12, soluble CD4 (sCD4), soluble CD8 (sCD8), IFN-γ, viral loads in each organ, APEC colonization, and so on. The results showed the development of immune organs in ducklings was affected, resulting in a decrease in the lymphocyte transformation rate (LTR), IL-12, sCD4, sCD8, IFN-γ and an increase in IL-10 content at 8 to 32 d postinfection (dpi). In the detection of virus loads in some organs, it was found that 8 dpi, DuCV existed stably in various organs, suggesting the importance of preventing and controlling the virus in the early stage of culture. The results of exploring the DuCV infection that shows some influence on secondary infection by APEC. The results showed that DuCV infection could significantly enhance the pathogenicity of APEC and the colonization ability of APEC in vivo. DuCV can induce more serious APEC infection in 24 dpi than in 14 dpi. Based on the above results, it can be concluded that DuCV infection will affect the immune system, cause immunosuppression, and lead to more serious secondary infection.

Pervasive RNA Regulation of Metabolism Enhances the Root Colonization Ability of Nitrogen-Fixing Symbiotic α-Rhizobia.

ABSTRACTThe rhizosphere and rhizoplane are nutrient-rich but selective environments for the root microbiome. Here, we deciphered a posttranscriptional network regulated by the homologous trans-small RNAs (sRNAs) AbcR1 and AbcR2, which rewire the metabolism of the nitrogen-fixing α-rhizobium Sinorhizobium meliloti during preinfection stages of symbiosis with its legume host alfalfa. The LysR-type regulator LsrB, which transduces the cell redox state, is indispensable for AbcR1 expression in actively dividing bacteria, whereas the stress-induced transcription of AbcR2 depends on the alternative σ factor RpoH1. MS2 affinity purification coupled with RNA sequencing unveiled exceptionally large and overlapping AbcR1/2 mRNA interactomes, jointly representing ⁓6% of the S. meliloti protein-coding genes. Most mRNAs encode transport/metabolic proteins whose translation is silenced by base pairing to two distinct anti-Shine Dalgarno motifs that function independently in both sRNAs. A metabolic model-aided analysis of the targetomes predicted changes in AbcR1/2 expression driven by shifts in carbon/nitrogen sources, which were confirmed experimentally. Low AbcR1/2 levels in some defined media anticipated overexpression growth phenotypes linked to the silencing of specific mRNAs. As a proof of principle, we confirmed AbcR1/2-mediated downregulation of the l-amino acid AapQ permease. AbcR1/2 interactomes are well represented in rhizosphere-related S. meliloti transcriptomic signatures. Remarkably, a lack of AbcR1 specifically compromised the ability of S. meliloti to colonize the root rhizoplane. The AbcR1 regulon likely ranks the utilization of available substrates to optimize metabolism, thus conferring on S. meliloti an advantage for efficient rhizosphere/rhizoplane colonization. AbcR1 regulation is predicted to be conserved in related α-rhizobia, which opens unprecedented possibilities for engineering highly competitive biofertilizers.

Plant life‐history traits rather than soil legacies determine colonisation of soil patches in a multi‐species grassland

Abstract Interactions between plants and soil biota are increasingly shown to play critical roles in plant species coexistence processes. Plant species coexistence is thought to be promoted via biotic legacies that plant species leave behind in the soil after a plant disappears. These soil legacies are hypothesised to supress colonisation success when the preceding plant is of the same species, that is, when a plant species encounters its own, species‐specific soil antagonists. However, colonisation of vacant spots in plant communities is in the first place determined by the ability of plants to reach such vacant locations. We currently lack an understanding of the explicit role of soil legacy effects and their relative contribution to colonisation processes in plant communities consisting of plant species inherently differing in colonisation ability. In experimental, outdoor plant communities consisting of eight grassland species, we tested the effect of five differently conditioned soil patches on plant species colonisation success over three consecutive growing seasons. We found that colonisation success was largely determined by the species' reproductive strategy, lateral spread and growth rate, and not by the plant species that conditioned the soil patch. Fast spreading, clonal plant species reached the soil patches first and initially attained the highest biomass inside the patch. One year later, slower spreading plant species colonised the patch via seedlings. Species with intrinsically high growth rates attained the highest biomass, decreasing biomass of the initial colonisers. While subtle differences between conditioned soil patches did occur, these were not strong enough to overcome the inherent differences in colonisation ability between the various plant species. Synthesis. Our results reject the hypothesis that colonisation of vacant soil patches in plant communities is strongly affected by the legacy that is left behind by the preceding plant species. Instead, plant species life‐history strategy plays a prominent role, driving sequential plant species replacements. Based on our results and recent accounts in literature we present a conceptual model for local cyclic dynamics in grassland communities, where soil legacy plays a role in affecting the performance of established plant species rather than colonisation of vacant patches.

Temperature-Dependent Reproductive Success of Stickleback Lateral Plate Morphs: Implications for Population Polymorphism and Range Shifts Under Ocean Warming

Changing environments associated with rapid climate change can shape direct measures of fitness such as reproductive success by altering mating behavior, fecundity and offspring development. Using a polymorphic oceanic population of threespine stickleback (Gasterosteus aculeatus), we investigated whether a 4°C increase in sea surface temperature influenced clutch siring success, reproductive output, and offspring growth among lateral plate morphs. Since low plated morphs are thought to have a selective advantage in warmer environments, we predicted that low plated males should have higher clutch siring success in +4°C environments, and that thermal plasticity of traits (e.g., egg size, offspring growth) should reflect different trait optima in different environments among plate morphs. Parentage analysis of egg clutches revealed temperature-specific clutch siring success, in that low plated males sired more clutches in +4°C environments and completely plated males sired more clutches at ambient (seasonal) temperature. Both completely and low plated females laid larger eggs when acclimated to +4°C, but only completely plated females had smaller clutches at +4°C. Offspring of low and partially plated females grew much less at +4°C compared to those of completely plated females. Taken together, our results demonstrate that ocean warming could impact reproductive success at various levels, with differential effects depending on phenotype, in this case, lateral plate morph. Some traits (clutch siring success, egg size) showed better performance for low plated fish at +4°C, whereas others (e.g., growth) did not. Higher clutch siring success of low plated males at elevated temperature might indicate a future shift in plate morph composition for polymorphic stickleback populations, with potential implications for colonization ability during range shifts under climate change.

P704 Bifidobacterium longum species protect murine colitis through different activation repertoires of immune cells

Abstract Background Inflammatory bowel disease (IBD) is a chronic disease that causes an inappropriate immune response due to genetic and environmental factors. The scientific interest in mechanisms of probiotics are world-widely growing. Bifidobacterium plays an essential role in the maturation of the immune system, and the prevention of colitis and tumor. However, only limited reports on bifidobacterium isolated to prevent colitis and their exact mechanisms of action remain poorly understood. This study identifies the different anticolitic effects between B. breve strain and Bifidobacterium longum (B. longum) strain, the most abundant probiotic strains in lactating babies. We explore the different activation repertoire of the immune cell according to Bifidobacterium species and the mechanisms in these processes. Methods We administrated B. breve and B. longum ATCC by oral gavage 1×109 CFU to RAG1 KO mice. Colitis was induced with 2.5% DSS for 7 days. To assess the direct role of B. longum on ILCs, ILCs from B. breve- and B. longum-treated wild-type mice were transferred to RAG1 KO mice. We observed daily weight loss, stool consistency, and rectal bleeding of mice and transformed to the disease activity index (DAI) scores. Macrophages and T-cell subsets in splenocytes, lamina propria cells were analyzed by flow cytometry. Gene expression and cytokine profiles were determined using qRT-PCR. We performed whole-genome sequencing of reactive oxygen species (ROS)-resistant B. longum species using DNA full-sequencing analysis. Results The two functional strains of B. breve and B. longum ameliorate gut immunopathology during colitis in RAG1 knockout mice. However, B. longum but not B. breve, drastically restored body weight loss, DAI, and colon length compared to B. breve-treated group. We found that the anticolitic effect of B. longum is specialized by modulation of ILCs. Newly identified B. longum strain from the feces of healthy adults has ROS resistance even though it is anaerobic bacteria. The new B. longum strain exhibits ANI values of 94.92% with respect to B. longum ATCC 15697. The new B. longum strain has a strong colonization ability and improves DSS-induced colitis in the wild-type mice than other strains. Our data revealed genus-specific effects of bifidobacteria on colonization in the colon, and ILCs, thus discriminating a differential degree of modulation of immune cells. Conclusion We explore the different activation repertoire of the immune cell according to Bifidobacterium species and the mechanisms in these processes. These findings suggest that B. longum can be used as a potent immunomodulatory of ILCs, which has significant implications for IBD treatment.

Genome-wide identification of bacterial colonization and fitness determinants on the floating macrophyte, duckweed

Bacterial communities associated with aquatic macrophytes largely influence host primary production and nutrient cycling in freshwater environments; however, little is known about how specific bacteria migrate to and proliferate at this unique habitat. Here, we separately identified bacterial genes involved in the initial colonization and overall fitness on plant surface, using the genome-wide transposon sequencing (Tn-seq) of Aquitalea magnusonii H3, a plant growth-promoting bacterium of the floating macrophyte, duckweed. Functional annotation of identified genes indicated that initial colonization efficiency might be simply explained by motility and cell surface structure, while overall fitness was associated with diverse metabolic and regulatory functions. Genes involved in lipopolysaccharides and type-IV pili biosynthesis showed different contributions to colonization and fitness, reflecting their metabolic cost and profound roles in host association. These results provide a comprehensive genetic perspective on aquatic-plant-bacterial interactions, and highlight the potential trade-off between bacterial colonization and proliferation abilities on plant surface.

Effects of Dietary Enterococcus faecalis YFI-G720 on the Growth, Immunity, Serum Biochemical, Intestinal Morphology, Intestinal Microbiota, and Disease Resistance of Crucian Carp (Carassius auratus)

Diseases of crucian carp (Carassius auratus) are closely related to intestinal parameters. Enterococcus faecalis has strong colonization ability in the intestinal tract, and produces natural antibiotics, bacteriocin, and other bacteriostatic substances, which can effectively inhibit some pathogenic bacteria and improve the intestinal microenvironment. This study aimed to assess the effects of E. faecalis YFI-G720 which was isolated from the intestinal of crucian carp on the growth, immunity, intestinal health, and disease resistance of crucian carp. Fish (48.16 ± 0.55 g) were fed four diets, commercial diet or diet containing E. faecalis at 105 CFU/g (EF1), 106 CFU/g (EF2), or 107 CFU/g (EF3) for 28 days. The results showed that supplementation of E. faecalis significantly improved the weight gain ratio (WGR) and the specific growth rate (SGR) compared with control group (p < 0.05). Intestinal mucosal epithelial cells in EF2 were intact and normal, but there was obvious vacuolation in CG. Compared with CG, serum C3 and IgM in EF2 were significantly increased at the end of the experiment (p < 0.05), and serum alkaline phosphatase was significantly higher in all experimental groups (p < 0.05). Among studied immune-related genes, expression was detected by qPCR, C3, IgM, and IL-1βwere upregulated in all experimental groups to varying degrees from 14 days, with highest expression in EF2 at 28 days. Intestinal microbiota structure analyzed through high-throughput sequencing, and the results showed that the relative abundance of Aeromonas and Acinetobacter decreased while Cetobacterium increased in all experimental groups, with the greatest changes in EF2. Challenge tests showed that fish fed E. faecalis were more resistant to Aeromonas veronii (p < 0.05). In conclusion, dietary E. faecalis YFI-G720 at 106 CFU/g can improve the health status, immune parameters, intestinal microbiota composition, and disease resistance of crucian carp.

Intra-Species Interactions in Streptococcus pneumoniae Biofilms.

Streptococcus pneumoniae is a human pathogen responsible for high morbidity and mortality worldwide. Disease is incidental and is preceded by asymptomatic nasopharyngeal colonization in the form of biofilms. Simultaneous colonization by multiple pneumococcal strains is frequent but remains poorly characterized. Previous studies, using mostly laboratory strains, showed that pneumococcal strains can reciprocally affect each other’s colonization ability. Here, we aimed at developing a strategy to investigate pneumococcal intra-species interactions occurring in biofilms. A 72h abiotic biofilm model mimicking long-term colonization was applied to study eight pneumococcal strains encompassing 6 capsular types and 7 multilocus sequence types. Strains were labeled with GFP or RFP, generating two fluorescent variants for each. Intra-species interactions were evaluated in dual-strain biofilms (1:1 ratio) using flow cytometry. Confocal microscopy was used to image representative biofilms. Twenty-eight dual-strain combinations were tested. Interactions of commensalism, competition, amensalism and neutralism were identified. The outcome of an interaction was independent of the capsular and sequence type of the strains involved. Confocal imaging of biofilms confirmed the positive, negative and neutral effects that pneumococci can exert on each other. In conclusion, we developed an experimental approach that successfully discriminates pneumococcal strains growing in mixed biofilms, which enables the identification of intra-species interactions. Several types of interactions occur among pneumococci. These observations are a starting point to study the mechanisms underlying those interactions.

Nitrogen fertilization differentially affects the symbiotic capacity of two co-occurring ectomycorrhizal species.

Forest trees rely on ectomycorrhizal (ECM) fungi to obtain growth-limiting nutrients. While addition of nitrogen (N) has the potential to disrupt these critical relationships, there is conflicting evidence as to the mechanism by which ECM:host mutualism may be affected. We evaluated how N fertilization altered host interactions and gene transcription between Eucalyptus grandis and Pisolithus microcarpus or Pisolithus albus, two closely related ECM species that typically co-occur within the same ecosystem. Our investigation demonstrated species-specific responses to elevated N: P. microcarpus maintained its ability to transport microbially sourced N to its host but had a reduced ability to penetrate into root tissues, while P. albus maintained its colonization ability but reduced delivery of N to its host. Transcriptomic analysis suggests that regulation of different suites of N-transporters may be responsible for these species-specific differences. In addition to N-dependent responses, we were also able to define a conserved 'core' transcriptomic response of Eucalyptus grandis to mycorrhization that was independent of abiotic conditions. Our results demonstrate that even between closely related ECM species, responses to N fertilization can vary considerably, suggesting that a better understanding of the breadth and mechanisms of their responses is needed to support forest ecosystems into the future.

Nucleomodulin BspJ as an effector promotes the colonization of Brucella abortus in the host.

Background Brucella infection induces brucellosis, a zoonotic disease. The intracellular circulation process and virulence of Brucella mainly depend on its type IV secretion system (T4SS) expressing secretory effectors. Secreted protein BspJ is a nucleomodulin of Brucella that invades the host cell nucleus. BspJ mediates host energy synthesis and apoptosis through interaction with proteins. However, the mechanism of BspJ as it affects the intracellular survival of Brucella remains to be clarified.ObjectivesTo verify the functions of nucleomodulin BspJ in Brucella's intracellular infection cycles.MethodsConstructed Brucella abortus BspJ gene deletion strain (B. abortus ΔBspJ) and complement strain (B. abortus pBspJ) and studied their roles in the proliferation of Brucella both in vivo and in vitro.ResultsBspJ gene deletion reduced the survival and intracellular proliferation of Brucella at the replicating Brucella-containing vacuoles (rBCV) stage. Compared with the parent strain, the colonization ability of the bacteria in mice was significantly reduced, causing less inflammatory infiltration and pathological damage. We also found that the knockout of BspJ altered the secretion of cytokines (interleukin [IL]-6, IL-1β, IL-10, tumor necrosis factor-α, interferon-γ) in host cells and in mice to affect the intracellular survival of Brucella.ConclusionsBspJ is extremely important for the circulatory proliferation of Brucella in the host, and it may be involved in a previously unknown mechanism of Brucella's intracellular survival.

Endophytic colonization of entomopathogenic Lecanicillium lecanii (Zimm) Zare & Gams PTN 10, and its effect on tobacco resistance against Myzus persicae Sulzer (Hemiptera: Aphididae)

Lecanicillium lecanii is a potential effective entomopathogen against various insect pests. Some isolates of Lecanicillium is also reported as endophytic. However, the information on endophytic colonization of L. lecanii PTN 10 and its role in conferring tobacco resistance against Myzus persicae is not available. The objective of the research was to determine the endophytic colonization ability of L. lecanii on tobacco plants and its effect on the biology and population growth of Myzus persicae. This research consisted of four treatments i.e. untreated plants (K), seed treated with conidia suspension of L. lecanii for 12 hours (P1), foliar spray using conidia suspension L. lecanii one week after transplanting (P2), and the combination of seed treatments and foliar spray. All treated tobacco plants were infested by first nymph of M. persicae one week after L. lecanii treatment. The observations include aspects of biology i.e. life cycle, fecundity, and the longevity of M. persicae. L. lecanii is proven able to colonize tobacco leaves endophytically. The fungus treatment on tobacco plants causes a prolonged life cycle, decreases fecundity, and significantly shortens longevity. Additionally, it suppresses population growth of M persicae.

Collar Rot Disease of Betelvine (Piper betle L.) under Coastal Saline Zone of West Bengal

Collar rot is an important disease of betelvine (Piper betle L.) caused by the soil borne fungus Sclerotium rolfsii Sacc. The pathogen was isolated from the infected vines cultivated in the coastal saline agro-climatic zone of West Bengal and characterized for its growth and survival under different pH, temperature and soil moisture. The pathogen was found to prefer acidic pH (optimum at pH 5.0 to 5.5) for its mycelial growth, formation of sclerotia and their germination. The saprophytic colonization ability of the fungus was drastically reduced at pH 7.7 and above. Germination of sclerotia was least at a soil moisture level of 20% of field capacity (FC). The increase in soil moisture increased the rate of sclerotial germination, resulting in quick loss of its viability. The saprophytic colonization ability of S. rolfsii was maximum at 60% of FC, which reduced rapidly above 70% of FC. The optimum temperature for maximum mycelial growth, sclerotial formation and its germination was 30±1°C. Mycelial growth, sclerotial formation, germination and saprophytic colonization ability of the fungus ceased completely at 40±1°C. These specific soil temperature and moisture requirements of the fungus S. rolfsii make the pathogen highly selective for its seasonal incidence and proliferation.

A COMPREHENSIVE NOTE ON TRICHODERMA AS A POTENTIAL BIOCONTROL AGENT AGAINST SOIL BORNE FUNGAL PATHOGENS: A REVIEW

The extensive use of synthetic pesticides has a harmful impact on the environment, plants and animal health. It is a big challenge for all farming systems to develop novel approaches, which are eco-friendly and improve food quality. As compared to synthetic pesticides, the use of beneficial microbes is the best option to maintain the environmental condition because they are cost-effective and ecofriendly. In the recent era, biological antagonistic microorganisms (Trichoderma spp.) are the best approach to control the soil-borne fungal pathogens associated with plant roots of agriculturally important crops. Due to fast growth and rhizospheric colonization ability, this fungus competes with other pathogenic soil-borne fungi by producing different metabolites (volatile and non-volatile). Trichoderma protected the plants from pathogenic fungi through mycoparasitic and antibiosis capability. Furthermore, it has the ability to improve plant health by inducing SAR (Systemic acquired resistance), ISR (Induce systemic resistance), producing antifungal enzymes (α-1, 3-glucanases, Trichodermaketone, and trichodermin) and antioxidant enzymes that strengthen the immune system by increasing activities of guaiacol peroxidase (GPX), ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD) after pathogen attack. Development of bio-fungicide formulation by using the spore of Trichoderma species (T. harzianum, T. viride, and T. virens) are most effective against soil-borne pathogenic fungi at different concentrations and temperatures. This review article has significantly focused on gathering and summarizing the most recent literature to highlight the visible production and application of Trichoderma as a biomonitoring and biocontrol agent in plant diseases management program.

Immune responses and inorganic ion transport regulations of Epinephelus coioides in response to L321_RS13075 gene of Pseudomonas plecoglossicida

Pseudomonas plecoglossicida is a well-known pathogen of viscera granulomas disease in fish, which has led to severe economic losses. In our previous study, L321_RS13075 was predicted to be a key virulence gene of P. plecoglossicida during the host-pathogen interaction with Epinephelus coioides. To investigate the role of L321_RS13075 in the regulation of virulence in P. plecoglossicida, a L321_RS13075 knock-down strain was constructed. And a significant reduction in the ability of colonization, intracellular survival, motility, biofilm formation, and adhesion was detected in the L321_RS13075 knock-down strain. Compared with the wild-type strain, the silence of L321_RS13075 in P. plecoglossicida resulted in a significant change in the transcriptome of infected Epinephelus coioides (E. coioides). Results of COG and GO analysis on E. coioides showed that genes related to immune responses and inorganic ion transport were significantly affected by L321_RS13075 of P. plecoglossicida. Meanwhile, the interactions of the genes related to immune responses and inorganic ion transport were predicted, and the important hub genes were identified. Taken together, the results indicated that L321_RS13075 was a virulent gene of P. plecoglossicida, which significantly affected the immune responses and inorganic ion transport in E. coioides.

Complete Genome Sequencing and Comparative Phenotypic Analysis Reveal the Discrepancy Between Clostridioides difficile ST81 and ST37 Isolates.

Toxin A-negative, toxin B-positive Clostridioides difficile strains, which primarily include the ST81 and ST37 genotypes, are predominant in C. difficile infections leading to antibiotic-associated diarrhea in China. Recently, ST81 has been reported as the most prevalent genotype rather than ST37, although the genetic and functional characteristics of the two genotypes remain ambiguous. In this study, we conducted comprehensive comparative analysis of these two genotypes through complete genome sequencing and phenotypic profiling. The whole genome sequencing revealed that the ST81 and ST37 isolates were closely related genetically with similar gene compositions, and high rate of the core genome shared. The integrative and conjugative elements identified in ST81 were similar to those in ST37, albeit with more diverse and insertion regions. By characterizing the phenotypes related to colonization or survival in the host, we found that the ST81 isolates exhibited robust colonization ability and survival both in vitro and in vivo, enhanced spore production, and slightly increased motility, which may be attributable to the discrepancy in non-synonymous single-nucleotide polymorphisms in the relevant functional genes. Furthermore, the ST81 isolates displayed a significantly higher rate of resistance to fluoroquinolones compared with the ST37 isolates (94.12% vs. 62.5%) and mostly carried the amino acid substitution Asp426Val in GyrB. In summary, the results of our study indicate that ST81 isolates exhibit enhanced ability to transmit between hosts and survive in harsh environments, providing key genetic insights for further epidemiological investigations and surveillance of C. difficile infection.

Into the range: a latitudinal gradient or a center-margins differentiation of ecological strategies in Arabidopsis thaliana?

Determining within-species large-scale variation in phenotypic traits is central to elucidate the drivers of species' ranges. Intraspecific comparisons offer the opportunity to understand how trade-offs and biogeographical history constrain adaptation to contrasted environmental conditions. Here we test whether functional traits, ecological strategies from the CSR scheme and phenotypic plasticity in response to abiotic stress vary along a latitudinal or a center- margins gradient within the native range of Arabidopsis thaliana. We experimentally examined the phenotypic outcomes of plant adaptation at the center and margins of its geographic range using 30 accessions from southern, central and northern Europe. We characterized the variation of traits related to stress tolerance, resource use, colonization ability, CSR strategy scores, survival and fecundity in response to high temperature (34 °C) or frost (- 6 °C), combined with a water deficit treatment. We found evidence for both a latitudinal and a center-margins differentiation for the traits under scrutiny. Age at maturity, leaf dry matter content, specific leaf area and leaf nitrogen content varied along a latitudinal gradient. Northern accessions presented a greater survival to stress than central and southern accessions. Leaf area, C-scores, R-scores and fruit number followed a center-margins differentiation. Central accessions displayed a higher phenotypic plasticity than northern and southern accessions for most studied traits. Traits related to an acquisitive/conservative resource-use trade-off followed a latitudinal gradient. Traits associated with a competition/colonization trade-off differentiated along the historic colonization of the distribution range and then followed a center-margins differentiation. Our findings pinpoint the need to consider the joint effect of evolutionary history and environmental factors when examining phenotypic variation across the distribution range of a species.