In the context of global warming, the rising frequency of extreme weather events, including high temperatures, rainstorms, and droughts, will directly or indirectly increase the risks of pathogenic microorganisms entering drinking water systems and source waters. This is attributable to an increase in terrestrial inputs or alterations to the conditions that facilitate microbial survival and growth. It is therefore imperative to give priority to the issue of drinking water biosafety. The development of novel pathogen detection methods and risk assessment models enables a more comprehensive understanding and assessment of the microbiological risks associated with drinking water in watersheds under climate change. This review outlines the sources of microbiological risks associated with drinking water in watersheds experiencing extreme climatic conditions and summarizes various microbial contaminations and their risks to human health. Furthermore, it emphasizes the significance of high-throughput quantitative microbial risk detection methods and assessment models in the control of microbiological risks to drinking water. Finally, it provides novel insights into the effective management and control of pathogenic microorganisms in drinking water under climate change.

Cyclic adenosine monophosphate (cAMP) is a second messenger widely present in eukaryotes. It is synthesized by adenylate cyclase (AC) and regulates downstream protein activity by binding to protein kinase A, thereby regulating fungal growth and development, virulence, cell wall integrity, environmental stress responses, and sexual/asexual reproduction. This article introduces the research progress of the cAMP signaling pathway in phytopathogenic fungi and the cooperation of this pathway with other signaling pathways in regulating cellular processes. At the same time, it elucidates the role of the cAMP signaling pathway in the infection of plant phytopathogenic fungi. This review is expected to provide reference for screening the agents for inhibiting phytopathogenic fungi that target the genes or proteins in the cAMP pathway. Additionally, the cAMP signaling pathway could be targeted to prevent and control the growth, development, and pathogenicity of phytopathogenic fungi in the future.

[Objective] To evaluate the safety and immunogenicity of outer membrane vesicles (OMVs) of Fusobacterium nucleatum prepared under the pH conditions simulating normal intestinal and tumor microenvironments, and to lay a foundation for the later development of OMV-based vaccines against F. nucleatum. [Methods] Ultra-high-speed centrifugation and density gradient centrifugation were employed to isolate the OMVs of F. nucleatum under different pH conditions. Three models of human colorectal cancer cells (HCT116), human colonic epithelial cells (HCoEpiC), and mouse macrophage Raw264.7 were infected by F. nucleatum. The cell proliferation was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and cell counting kit-8 (CCK-8) assay, and the cell apoptosis were evaluated by flow cytometry and in situ fluorescence of adherent cells. The safety in vivo was detected by blood routine and whole blood index of mice. The enzyme-linked immunosorbent assay (ELISA) was employed to examine the cell immunogenicity, and the adhesion inhibition assay was conducted to assess cell immunoprotection. [Results] Acidic outer membrane vesicles (aOMVs) and neutral outer membrane vesicles (nOMVs) had no significant different effects on the proliferation or apoptosis of HCoEpiC, HCT116, and Raw264.7 cells. Both nOMVs and aOMVs at a concentration of 25 μg/mL did not lead to significant hemolysis of red blood cells, and the routine blood and whole blood test results of the mice treated with aOMVs were within the normal ranges. The results demonstrated that both aOMVs and nOMVs exhibited good immunogenicity and reduced the adhesion of F. nucleatum to colon cancer cells DLD-1. The aOMVs outperformed nOMVs regarding immunogenicity. [Conclusion] Both aOMVs and nOMVs had good safety and immunogenicity, and aOMVs were superior to nOMVs.

[Objective] To investigate the antibiotic resistance profiles, resistance genes, and bla_NDM transmission characteristics of bacterial isolates from six turtle farms in two regions (three in Lanxi (LX) and three in Xiaoshan (XS)) of Zhejiang Province. [Methods] Bacterial strains were identified by 16S rRNA gene sequencing. The Kirby-Bauer method was employed to examine the antibiotic susceptibility of isolated bacteria. PCR was employed to detect resistance genes carried by the isolated bacteria. Conjugation transfer experiments were conducted to obtain bla_NDM-carrying plasmids, and the conjugation frequency was analyzed to assess the transfer capabilities of bacterial donors. Additionally, the modified Carba NP test, plasmid replicon typing, and minimum inhibitory concentration determination were carried out to evaluate the transmission of bla_NDM-carrying plasmids among bacteria. [Results] A total of 244 bacterial strains were isolated, with similar distribution between the two regions and Enterobacteriaceae being dominant. PCR amplification of integrons revealed various resistance genes, including those conferring resistance to aminoglycosides and trimethoprim. We identified numerous resistant bacteria capable of integrating additional exogenous resistance genes. All the isolated strains exhibited resistance to at least one antibiotic, with some displaying resistance to carbapenems. PCR detection of resistance genes indicated the dissemination of carbapenem resistance genes within some farms. This study confirmed the presence of bla_NDM on plasmids capable of inter-bacterial transmission. Moreover, the farms in LX exhibited significantly higher conjugation frequency of bla_NDM-carrying plasmids than the farms in XS. [Conclusion] Antibiotic resistance of bacteria in aquaculture environments is becoming increasingly serious. The carbapenem resistance gene bla_NDM has spread within turtle farms.

Heterotrophic nitrification and aerobic denitrification microorganisms (HNADMs) can complete both nitrification and denitrification under aerobic conditions, which paves a new way for biological nitrogen removal. Researchers have discovered that some HNADMs maintain high nitrogen removal efficiency in extreme environments, exhibiting high application potential in the nitrogen removal of atypical wastewater. However, the available studies on HNADMs in extreme conditions remain in the initial stage. This article introduces the diversity, physiological and biochemical characteristics, and the complexity of metabolic pathways of HNADMs. Particularly, it reviews the research progress in HNADMs regarding the tolerance mechanisms to extreme temperature, pH, high salt, oligotrophic, and heavy metal stress conditions, nitrogen removal efficiency of simultaneous nitrogen and phosphorus removal, degradation of complex organic matter, and antibiotic resistance. Furthermore, the application status of HNADMs in extreme environments is summarized. Finally, the bottlenecks in the application of HNADMs in extreme environments are prospected. The review is expected to provide basic data for the application of HNADMs in complex wastewater treatment.

A mutant (G₉-72) of Halomonas campaniensis exhibiting high ectoine production was obtained by ultraviolet (UV) mutagenesis. The mutation sites, molecular variations, and high ectoine production mechanism of this mutant remain unknown.[Objective] To investigate the mutation sites and genetic variations of G₉-72 compared with the wild type strain XH26 and identify the potential causes of ectoine accumulation outbreak. [Methods] PacBio Sequel Ⅱ was used for whole-genome sequencing, and the mutation sites in the genome of the mutant were identified based on the sequencing results. The amino acid metabolic pathways were analyzed to reveal the association between mutated genes and ectoine synthesis, and the results were verified by RT-PCR. [Results] The genome of strain XH26 was 4.11 Mb, encoding 3 927 genes. Compared with strain XH26, G₉-72 showed 35 mutation sites, including 18 single nucleotide polymorphism mutations, 14 insertion mutations, and 3 deletion mutations. The mutated genes argF, coaBC, and livH, which encoded ornithine transcarbamylase (100.00% similarity with ArgF proteins in NCBI database), phosphopantothenoylcysteine decarboxylase (99.28% similarity with CoaBC proteins in NCBI database), and branched-chain amino acid ABC transporter permease (96.27% similarity with LivH proteins in NCBI database), were implicated in the synthesis of fumaric acid, citric acid and the absorption and transport of branched-chain amino acids, respectively. The increased flow of upstream metabolites may be the key reason for the sharply increased accumulation of ectoine in the mutant. RT-PCR verified 20 genes related to the ectoine metabolic pathway, and the transcriptional expression levels were consistent with the expected analysis. [Conclusion] The overexpression of genes argF, coaBC, and livH enhanced the anabolic flow of ectoine, which contributed to a significant increase in ectoine accumulation in the mutant. This finding provides a reference point for subsequent studies on the reaction mechanisms of enzymes in the mutant and the fermentation production.

[Objective] To study the plant disease-inhibiting and growth-promoting effects and identify the antimicrobial components of Streptomyces levis L2. [Methods] Morphological features and the phylogenetic tree based on the 16S rRNA gene sequences were employed to identify the strain L2 isolated from the rhizosphere of drought-tolerant Echinochloa crusgalli. The antimicrobial components produced by the strain were identified by chromatography and high-resolution mass spectrometry. The whole genome of the strain was sequenced by Illumina in combination with Nanopore. antiSMASH was employed to search for the biosynthetic gene clusters. [Results] Streptomyces levis L2 and its fermentation broth inhibited the growth of Gram-positive bacteria and phytopathogenic fungi, and the strain produced a large transparent zone on the CAS (chrome azurol sulphonate) plate and could produce indole-3-acetic acid (IAA). The antimicrobial components of the strain showed the m/z of 537.102 0 [M+H]⁺ (calcd for C₂₇H₂₀O₁₂, 537.103 5, 2.2×10^–6) and 523.086 3 [M+H]⁺ (calcd for C₂₆H₁₈O₁₂, 523.087 8, 2.9×10^–6), which were consistent with the exact masses of α-rubromycins, β-rubromycins and γ-rubromycins, with the errors less than parts per 5 million. Their HPLC retention time were in agreement with that of standard rubromycins. The whole genome of L2 had a length of 8.8 Mb and carried 32 biosynthetic gene clusters for secondary metabolites including rubromycins. [Conclusion] S. levis L2 exhibited excellent plant disease-inhibiting and growth-promoting properties, thus could be further developed as biocontrol agents. It produces the antimicrobial components rubromycins and its biosynthetic gene clusters contained 6 more modification genes than the previously published gene clusters for rubromycins and several genes with unknown functions.

[Objective] To study the effects of endoplasmic reticulum stress on the regulation of the lifespan and autophagy of Saccharomyces cerevisiae by the protein O-mannosyltransferase 1 (PMT1). [Methods] The double deletion strain (pho8Δ60 pmt1Δ) was constructed based on the genetic homologous recombination. The daughter cells produced by the mother cell of the PMT1-deleted yeast strain (pmt1Δ) treated with tunicamycin (inducing endoplasmic reticulum stress) were counted under a light microscope, and the replicative lifespan of the strain was examined. A microplate reader was used to measure the alkaline phosphatase activity of the pho8Δ60 pmt1Δ strain in the SD-N medium (for inducing autophagy). Western blotting was employed to determine the expression level of the autophagy marker Atg8 in the presence of tunicamycin. The transcript levels of autophagy-related genes ATG1 and ATG8 in the pmt1Δ strain treated with tunicamycin were determined by RT-qPCR. [Results] The replicative lifespan of the pmt1Δ strain was shortened by 38.7%, while the alkaline phosphatase activity of pmt1Δ strain was increased compared with those of the wild type in the presence of tunicamycin. The expression levels of GFP-Atg8 fusion protein and free GFP in the pmt1Δ strain were up-regulated with the increase in the concentration of tunicamycin. The transcript levels of ATG1 and ATG8 were up-regulated in the pmt1Δ strain treated with tunicamycin. [Conclusion] Endoplasmic reticulum stress impairs the replicative lifespan and enhances the autophagy of PMT1-deleted yeast cells.

Probiotics refer to live microorganisms that are beneficial to the health of the host when ingested in sufficient quantities, and their beneficial effects have been widely recognized. However, the probiotic function of probiotics is strain-specific. As more and more emerging technologies are introduced into the research on probiotics, the screening of probiotics with specific functions according to individual needs has become a research hotspot. Conventional probiotic screening methods have limitations and cannot meet the current demand for precision medicine. Therefore, a bottom-up precision screening strategy for probiotics based on phenotyping, genotyping, and target is of great practical significance. This article discusses the theoretical basis, methods, and technologies of accurate screening of probiotics from phenotype, genotyping, and target, and the application and safety evaluation of probiotics, aiming to provide reference for the accurate screening of probiotics.

The nitrogen fixation in legume root nodules is of great significance for sustainable agricultural development and natural eco-environment protection. The growth period of root nodules can be divided into young, active, and senescence stages. Root nodule senescence is a complex physiological process involving the interactions of multiple genes and environmental factors. The functions and lifespan of root nodules can be altered by regulating nitrogenase activity and leghemoglobin gene expression levels. Biotic and abiotic stresses can accelerate the senescence of root nodules and reduce the biomass and productivity of leguminous plants. This article expounds the mechanism of morphological, physiological, biochemical, and molecular changes of root nodules during senescence and summarizes the biotic and abiotic factors that affect root nodule senescence. Furthermore, the measures for delaying the senescence of root nodules are discussed. These measures will prolong the symbiotic nitrogen fixation, improve the nitrogen utilization efficiency, and increase the overall nitrogen supply for seed filling of leguminous plants, thereby enhancing food security and reducing the adverse effects of chemical fertilizers on the environment.