[Objective] To investigate the biosynthetic potential of the endophyte Streptomyces sp. SZC001 in Sinomenium acutum and explore the unknown active natural products. [Methods] SZC001 was isolated by surface sterilizing method and its full-length genome sequence was obtained by third-generation and second-generation sequencing. Then, the biosynthetic potential of SZC001 was evaluated by antiSMASH analysis. Fermentation was carried out with four media, and the compounds were separated and identified by silica gel column chromatography, high-performance liquid chromatography, high-resolution mass spectrometry and nuclear magnetic resonance. The CCK-8 assay was employed to examine the cytotoxicity of the target compounds. [Results] The strain was identified as Streptomyces sp. SZC001, with a genome length of 9 109 166 bp and the G+C content of 71.08%. The antiSMASH analysis showed that the genome of the strain contained a total of 31 biosynthetic gene clusters (BGCs), among which 17 BGCs had less than 40% similarity with the known BGCs. The strain produced several anthracyclines in four media, and the two most abundant compounds 1 and 2 were isolated and identified. Compound 1 is the known compound ε-rhodomycinone and compound 2 is a new compound η-rhodomycinoe, which is derived from α₂-rhodomycinone by derivatization of the hydroxyl group at the C-10 position and transfer of the hydroxyl group at the 6-position to the 11-position of the backbone. Both compounds 1 and 2 showed relatively strong inhibitory effects on two tumor cell lines, with IC₅₀ of 1.55–4.59 μmol/L. [Conclusion] SZC001 is a strain that holds the potential for the exploration of active natural products. The anthracyclines produced by the strain exhibit anti-tumor activities and warrant further development and utilization. This study enriches ε-rhodomycinone derivatives, furnishing a foundation for the subsequent exploitation of the endophytic resources of S. acutum.

Although the large scale of industrial nitrogen fixation and chemical nitrogen fertilizer application have increased crop yields and alleviated food crisis, the excess discharge of nitrogen nutrients have affected the environment and human health. The treatment of nitrogen contamination is largely dependent on the nitrogen cycle driven by microorganisms. In the last three decades, researchers have discovered the inorganic nitrogen metabolism pathways such as anaerobic ammonia oxidation (Anammox), complete ammonia oxidation (Comammox), and direct ammonia oxidation (Dirammox). Shewanella, a genus of known bacteria with abundant respiration pathways, are ubiquitous in natural habitats and have potential applications in both microbial fuel cells and environmental bioremediation. In this review, we described the modulation mechanisms of denitrification and dissimilatory nitrate reduction to ammonium pathways in Shewanella from the nitrate reductase systems, regulation of the cyclic AMP (cAMP) receptor proteins (Crp), and modulation and switching of nitrate reduction pathways, aiming to give insights into the microbial-driven nitrogen cycling mechanism in the hydrosphere and the development of novel biotechniques and bioreactors for the removal and mitigation of nitrogen pollution.

Cable bacteria are a new group of filamentous electroactive microorganisms with the ability of long-distance electron transfer (LDET), playing an important role in the geochemical cycling of elements. Their unique structural and functional characteristics make them like "biological cables". Since the first discovery in marine sediments in 2012, cable bacteria have attracted widespread attention. They have shown unique ecological potential in maintaining the health of aquatic ecosystems, environmental restoration, and climate regulation. Focusing on the "biological cable" structures and functions of cable bacteria, this paper reviews their filamentous structural characteristics, electrogenic sulfur oxidation characteristics, diversity and distribution characteristics, and LDET mechanism in sediments, and summarizes their influences on the cycling of key elements such as S, C, N, and P and the migration and transformation of metal ions. In addition, this paper summarizes the interactions of cable bacteria with other organisms and their roles in the natural restoration of ecosystems and analyzes the existing problems and future development directions, with a view to providing a reference for further giving play to the role of "biological cables" in the natural restoration of ecosystems.

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 reveal the dynamics of bacterial communities in surface water and groundwater in the densely populated area of the Jianghan Plain across seasons and explore the underlying factors causing the temporal variations. [Methods] Water samples were collected from both surface water and groundwater in the densely populated area of the Jianghan Plain, and metagenomic sequencing was employed to investigate the seasonal variations of bacterial communities. The variations in environmental factors, bacterial community structure, and bacterial community assembly processes in the surface water and groundwater were compared considering rainy and dry seasons. [Results] For the surface water, the salinity (P < 0.01) and conductivity (P < 0.01) during the rainy season were lower than those during the dry season, while no significant seasonal variation was observed in turbidity. For the groundwater, the turbidity was higher in the rainy season than in the dry season (P < 0.05), while neither salinity nor conductivity showcased seasonal variations. The Shannon index of bacteria in the surface water in the rainy season was higher than that in the dry season (P < 0.01), whereas that in the groundwater presented no significant seasonal difference. The principal coordinates analysis and permutational multivariate analysis of variance (P=0.001) revealed significant seasonal variations in bacterial communities between surface water and groundwater. The Mantel test showed no significant correlations between the bacterial community in the groundwater and environmental factors during the dry season, while other communities were significantly correlated with at least one environmental factor. The neutral community model, modified stochasticity ratio (MST), and β nearest taxon index all indicated that stochastic processes exerted stronger effects on the bacterial community in the surface water during the rainy season than during the dry season, and the trend was similar but not significant for the bacterial community in the groundwater. The migration rate of surface water was higher during the rainy season than during the dry season, whereas that of groundwater showed an opposite trend. (5) The seasonal variations in the diversity of antibiotic resistance genes exhibited a negative correlation with MST (ρ=−0.164, P=4.942E−2) in the surface water, whereas the correlation was positive in the groundwater (ρ=0.393, P=1.452E−6). [Conclusion] The temporal dynamics of bacterial communities in surface water and groundwater in the densely populated area of the Jianghan Plain showed notable differences. These differences can potentially be attributed to distinct basic properties between surface water and groundwater, frequent environmental disturbances during the rainy season, and water exchange processes between surface water and groundwater.

Dissolved organic matter (DOM) in the ocean encompasses complex and diverse organic compounds, and heterotrophic bacteria, the main DOM decomposers, also exhibit high biodiversity. The interactions between heterotrophic bacteria and DOM play an important role in biogeochemical cycles, which, however, are not fully understood.[Objective] To explore the dynamics of microbial communities with the addition of marine-derived concentrated DOM. [Methods] DOM with a molecular weight exceeding 1 kDa and enriched from coastal seawater was introduced into microcosm culture systems. Illumina amplicon sequencing, dissolved organic carbon (DOC) concentration measurement, and bacterial isolation were performed on different days of incubation. [Results] The addition of DOM significantly influenced bacterial community composition, inducing more pronounced changes in the high-DOM group. Specifically, the relative abundance of Campylobacterota, Nitrosococcales, and Nitrincolaceae increased in the high-DOM group on days 3, 10, and 30, respectively. The alpha diversity and evenness of the microbial community decreased during days 0-3 and increased during days 10-30, with a transition point occurring between days 3 and 10. The network analysis revealed that the high-DOM group exhibited a more tightly interconnected and complex network than the control group. In addition, bacterial isolates from the culture systems added with different concentrations of DOM were distinct. The specific genera of different DOM treatments were identified, which may be key groups in DOM degradation. [Conclusion] The addition of DOM triggers the succession of microbial community structures within microcosm culture systems, and the community composition may be associated with specific DOM components, which influence the direction of community succession. Furthermore, the varying DOM concentrations select for culturable bacteria with diverse survival strategies. This study provides a basis for enriching our understanding about the mechanisms underlying microbial responses to marine-derived DOM.

Higher alcohols, major metabolic byproducts produced by Saccharomyces cerevisiae during winemaking, are intricately regulated by a multilevel system. While the enzymatic machinery and their encoding genes involved in the metabolic pathways of higher alcohols in S. cerevisiae have been largely elucidated, the transcriptional regulation underlying this process remains poorly understood. This paper, building upon a summary of the metabolic pathways and regulatory strategies of higher alcohols metabolism in yeast, focuses on the transcription factors Aro80p, GATA and Leu3p implicated in the regulation of higher alcohols metabolism in yeast and their mechanisms of action. The review aims to give theoretical insights into a comprehensive understanding of the transcriptional regulation of higher alcohols metabolism in yeast and facilitate the breeding of yeast strains with moderate production of higher alcohols.

Cyanobacteria have garnered great attention as important players in the marine hydrosphere and the source of bioactive compounds. Type Ⅳ pili (TFP) play a crucial role in cyanobacteria by participating in various physiological functions such as substrate surface movement, phototaxis, and natural transformation. With the continuous advancements in the visualization of pili, we have gained a deeper understanding of the TFP-mediated cell behaviors of cyanobacteria. We review the recent progress and applications of visualization of pili in the research on the twitching, phototaxis, and natural transformation of cyanobacteria. This review is expected to improve our understanding of the TFP-mediated cell behaviors and the ecological function and significance of cyanobacteria in the hydrosphere. Additionally, it provides new insights for developing TFP-based regulation on cell behaviors of cyanobacteria.

Marine mammals mainly include Cetacea living in the water, Sirenia primarily inhabiting water, and Pinnipedia which are amphibious. All these animals are rare and included in the list of national second-class or higher protected animals. Microorganisms play crucial roles in nutrient absorption, assisting the digestive process, and enhancing immune function of mammals, being an indispensable component of the host. The unique living conditions and diets of marine mammals result in significant differences in their microbiomes compared with terrestrial mammals. As a result, our knowledge about the microbiomes derived from terrestrial mammals is not applicable to marine mammals. Therefore, understanding the structures and functions of marine mammal microbiomes is essential for comprehending the interactions between marine mammals and their living environment and enhancing conservation efforts. This paper summarizes the recent advances in research on the microbiomes of marine mammals, discusses relevant technical methods, and highlights worthy scientific issues in future research.