World journal of microbiology & biotechnology最新文献

Aquaculture plays a vital role in ensuring global food security. However, the use of Artemia as crucial live food in the hatchery industry is often limited by cost, availability, and nutritional variability. This study investigated the potential of Purple Non-Sulphur Bacteria isolates, specifically Rhodopseudomonas sp. strain AZR1 and Rhodopseudomonas sp. strain AZW1, isolated from a mangrove ecosystem in Terengganu, Malaysia, as a sustainable feed supplement for Artemia. Following 16 S rRNA gene sequencing, these strains were characterized for growth kinetics, carotenoid production, nutritional composition, and fatty acid profiles to determine the best isolate for use as Artemia feed. Strain AZR1 outperformed strain AZW1, exhibiting higher growth rates (maximum 4.93 g/L dry cell weight vs. 3.9 g/L), better carotenoid production (10.16 mg/g vs. 7.68 mg/g), and enhanced nutritional values (53.17% protein, 7.77% lipid vs. 50.55% protein, 6.76% lipid), with elevated levels of astaxanthin (0.324 µg/mL vs. 0.254 µg/mL) and β-carotene (0.228 µg/mL vs. 0.16 µg/mL). Subsequently, strain AZR1 was evaluated as a diet for Artemia franciscana under both hatchery and small-scale Artemia test conditions, comparing its effects to Baker's yeast (control) and a Palm Kernel Cake by-product (PKC Nutri+). Results revealed that Artemia fed with strain AZR1 displayed significantly improved growth (length 9.6-10.11 mm), enhanced water quality (low ammonium concentrations: 2 mg/L vs. 8 mg/L for both yeast and PKC Nutri+), increased resistance to Vibrio campbellii (91.67% survival after challenge with 10⁸ cells/mL), upregulated expression of immune-related genes (Hsp70, Hsp90, proPO), and superior nutritional profiles (50.96% protein, 6.62% lipid, enhanced carotenoid composition) compared to the other feeds. However, while PKC Nutri + exhibited higher levels of polyunsaturated fatty acids (PUFAs), strain AZR1 presented a safer, healthier, and mycotoxin-free alternative. This study demonstrates the potential of strain AZR1 as a promising candidate for sustainable single-cell protein (SCP) production, and its beneficial effect on Artemia growth performance, nutritional quality, disease resistance, and immune function.

Despite the extensive use of chemical controls in weed management programs, the effect of herbicides on soil microbial communities is inconclusive. In this study, the effects of glufosinate-ammonium (T1) and metsulfuron-methyl (T2) application at the recommended rate (495 g a.i./ha and 15 g a.i./ha) on the soil bacterial communities within an oil palm plantation were investigated using 16 S rRNA gene high-throughput sequencing. Herbicides were applied in the rhizosphere area of oil palms, and soil microbial communities were assessed over multiple time-points, for 9 months. Herbicides did not drastically influence the alpha or beta diversity of the soil bacterial community, but a significant decrease in the Shannon and inverse Simpson diversity indices was observed at 6 months after application (MAA) and recovered at 9 MAA in T2. The relative abundance of selected beneficial soil bacteria strains was stable across both herbicide treatments and sampling times. FAPROTAX functional profile prediction showed minimal influence of herbicides on soil bacterial activity and functions. The complexity and stability of the bacterial network had increased in T1 but were reduced in the rhizosphere soil in T2. Herbicide application was shown to increase the abundance of the bacterial phylum Latescibacterota, which may have the potential to metabolise chemical compounds that could be explored for future bioremediation use. Our results suggested that application of glufosinate-ammonium and metsulfuron-methyl at the recommended rate may not adversely affect soil bacterial communities or their functions in oil palm plantations.

Kluyveromyces marxianus is a fast-growing, food-grade yeast with broad substrate utilization, however, its limited expression tools hinder its synthetic biology applications. Here, we developed single- and dual-gene expression systems based on screened elements, including a promoter pENO and a bidirectional promoter pHTX. These systems enabled stable expression across multiple K. marxianus strains, with expression levels affected by genetic element combinations, carbon source, and culture time. Using the single-gene system with a short intergenic sequence (IGG) for bicistronic expression, the production of leghemoglobin from Vigna angularis (VaHB) reached 30.4 mg/L using galactose as carbon source. In contrast, the dual-gene system achieved 48.4 mg/L of VaHB with the co-expression of HEM1, enhancing heme biosynthesis using glucose as a carbon source. Additionally, Simian Virus 40 (SV40) nuclear localization signals (NLS) directed fluorescent proteins to the nucleus, enabling subcellular targeting. This toolkit supports efficient and context-responsive gene expression in K. marxianus, facilitating its development as a versatile microbial chassis for industrial protein production and synthetic biology applications.

Quorum Sensing (QS) inhibition has become a promising strategy to fight bacterial infection since it inhibits pathogenesis without killing the bacteria. The present study has explored the anti-QS and anti-biofilm activity of Epigallocatechin-3-gallate (EGCG), a major phyto-constituent of green tea. EGCG showed a significant reduction in biofilm formation, violacein, exopolysaccharide, protease production, and swarming motility in Chromobacterium violaceum ATCC 12472 at different sub-inhibitory concentrations (25-150 µg/ml). Its efficacy was checked along with an antibiotic drug, tetracycline, with reported anti-QS potential. EGCG didn't hamper the growth of the bacterium up to 75 µg/ml concentration, but inhibited QS-related factors. Transcriptomic profiling of differentially expressed genes (DEGs) in EGCG and tetracycline-treated bacterial cells demonstrated that EGCG led to significant downregulation of QS-related genes, particularly those within the CviI/CviR circuit (cviI, cviR, and vioABCDE). In contrast, tetracycline exhibited a broader suppression of essential metabolic genes, reflecting its general bactericidal activity. Quantitative RT-PCR analysis validated that EGCG significantly reduced the expression of QS-related genes in C. violaceum. Our proposed pathway for EGCG-mediated QS inhibition pointed towards the EGCG's interaction with the CviR protein. Molecular docking and dynamic simulation studies predicted that EGCG binds stably to the CviR, potentially obstructing its interaction with the autoinducer and subsequent DNA binding. This study promotes EGCG as an effective QS inhibitor, which could help develop anti-bacterial medications targeting quorum sensing.

Hypereutrophic freshwater systems, characterized by elevated bacterial biomass and activity, efficiently process organic matter through bacterial production and respiration, summarized as bacterial growth efficiency (BGE). Yet, the factors controlling BGE, particularly viral influences, remain underexplored. This study examined the interactive effects of bottom-up (nutrient-driven) and top-down (viral) controls on BGE over a one-year period in the pelagic zone of Lake Fargette (France). BGE exhibited a clear seasonal pattern, ranging from 23% to 60% (mean = 40.0 ± 9.9%), and was significantly correlated with organic carbon, total nitrogen, and C: N ratio, indicating control by substrate availability. Significant relationship between bacterial production and respiration suggests a stable and tightly coupled balance between anabolic and catabolic processes under resource-rich conditions. Increased input of labile organic matter sustained an active, high nucleic acid bacterial community and enhanced elevated viral abundance and production. Viral mediated lysis rate was positively correlated (p < 0.001) with BGE, indicating that viral activity was resource-modulated rather than host-limited. Elevated substrate supply appeared to favor rapid bacterial growth that outpaced viral infection cycles, maintaining high BGE despite strong lytic pressures. These findings underscore the complex interplay between resource availability and viral lysis in regulating bacterial carbon dynamics within hypereutrophic freshwater ecosystems.

Central line-associated bloodstream infections (CLABSIs) pose a serious threat to critically ill patients, particularly in low- and middle-income countries facing rising antimicrobial resistance (AMR). Integrating WHO's Priority Pathogen Lists (PPL) and AWaRe antibiotic classification into CLABSI surveillance provides a clinically meaningful framework to guide antimicrobial stewardship and infection control. We conducted an observational study in ICUs from 2021 to 2024. Patients with central lines in situ for ≥ 2 calendar days were evaluated using CDC-NHSN definitions. Isolates underwent antimicrobial susceptibility testing (CLSI M100). Pathogens were classified using WHO PPL 2024 and analysed as per AWaRe categories. Clinical outcomes were correlated with pathogen class and resistance profile. Among 5,398 ICU patients, 102 developed laboratory-confirmed CLABSIs. Of these, 76.5% were caused by WHO-priority pathogens-63 bacterial and 15 fungal. Carbapenem-resistant Klebsiella pneumoniae and Acinetobacter baumannii predominated, especially in trauma ICUs (88.6%, p = 0.0493). Over 95% of bacterial isolates were resistant to all Access and Watch antibiotics, necessitating the use of Reserve agents like colistin. Among fungal isolates, Candida auris emerged as the most resistant species, while C. tropicalis retained full susceptibility. Mortality was 100% in patients infected with high-priority bacterial pathogens and 85.7% with high-priority fungal pathogens. This study is the first to map CLABSIs against the WHO PPL and AWaRe frameworks, highlighting a convergence of high-risk infections, therapeutic exhaustion, and poor outcomes. The findings underscore the urgent need for targeted stewardship, enhanced surveillance, and policy-level AMR interventions in critical care settings.

Butyric acid, a short-chain organic acid, is extensively used in the chemical, food, and pharmaceutical industries. Given the constraints in raw materials for traditional chemical synthesis and the rising consumer preference for natural products, microbial fermentation has emerged as a promising and sustainable alternative for butyric acid manufacture. This review provides a detailed elaboration of four biosynthetic pathways for microbial butyric acid production. It summarizes recent advances in butyric acid producers, encompassing both natural producers like Clostridium and emerging producers such as Escherichia coli. Their fermentation performance is systematically compared based on key metrics, including yield, tolerance, substrate utilization range, and process maturity. Butyric acid production was improved through targeted metabolic engineering and optimized fermentation processes, working in concert to enhance overall biosynthesis efficiency. Finally, it concludes with a summary and a perspective on future research priorities, which are anticipated to focus on systems metabolic engineering and integrated bioprocess development to enhance economic feasibility.

The phyllosphere, encompassing the aerial surfaces of plants, represents one of the largest microbial habitats on Earth and plays a pivotal yet underutilized role in sustainable agriculture and environmental health. Colonized by diverse bacterial, fungal, and yeast communities, the phyllosphere microbiome significantly influences plant growth, disease resistance, nutrient dynamics, and abiotic stress tolerance. These microorganisms engage in complex interactions with host plants, often functioning as biofertilizers, biopesticides, and stress protectants by producing phytohormones, antimicrobial metabolites, and stress-responsive compounds. Importantly, phyllospheric microbes also contribute to atmospheric and ecological balance by participating in carbon and nitrogen cycling, degrading volatile organic compounds (VOCs), and mitigating air pollution. However, despite their immense potential, the practical application of phyllospheric microbes remains limited by challenges such as environmental instability, poor field persistence, and incomplete functional characterization. The highly variable microclimate of the leaf surface poses survival barriers to both native and introduced microbial inoculants. Moreover, the specificity of plant-microbe associations and the complexity of microbial interactions necessitate precision-based approaches for successful deployment. Recent advances in omics technologies, microbial consortia engineering, and nano-enabled delivery systems provide new opportunities to overcome these limitations. A deeper understanding of phyllosphere microbial ecology, combined with innovations in synthetic biology and ecological modeling, can facilitate the development of robust microbial tools tailored to specific crops and climates. Harnessing the potential of phyllospheric microorganisms is not merely an academic pursuit, it is a strategic imperative for transitioning toward climate-resilient, low-input, and ecologically sound agricultural systems.

Biofilms are surface-attached bacterial consortia, which account for 80% of the world's microbial biomass, and are responsible for 75% of human infections. These surface bacterial communities have enhanced their ability to withstand unfavourable conditions and resist antimicrobial treatments due to the presence of outer membrane proteins (OMPs). Outer membrane proteins (OMPs) play a central role in biofilm formation by mediating adhesion, matrix assembly, and intercellular interactions, and they are increasingly being targeted for novel antibacterial therapies to disrupt biofilm-related infections. OMPs play a crucial role in biofilm formation, as these proteins contribute to the assembly and architecture of the biofilm matrix, interact with other matrix proteins, and influence surface hydrophobicity and cell aggregation. Notably, genetic modifications or deletions of OMPs can increase or decrease biofilm formation, indicating their regulatory influence on matrix composition and biofilm morphology. Incidentally, biofilm poses significant challenges in industry and abiotic medical equipment. OMPs offer excellent targets to mitigate biofilm-forming infections, since blocking their function can reduce bacterial adhesion and disrupt biofilm integrity. Furthermore, antimicrobial peptides as well as nanotechnology-based therapeutics are under development to target OMPs, allowing for innovative approaches that circumvent traditional resistance mechanisms seen in biofilms. This review underscores the significance of key OMPs in devising strategies to combat biofilm-associated infections and offers a concise overview of their structure, function, and immunoprotective role. By targeting outer membrane proteins, emerging therapies seek to address the persistence and antibiotic resistance of biofilm-forming bacteria, representing a promising direction in the treatment of chronic and multidrug-resistant infections.

Abiotic stresses such as salinity, drought, heat, and ultraviolet radiation are among the most serious constraints on global crop productivity. These stresses disrupt photosynthesis, nutrient uptake, and cellular redox balance, leading to major agricultural losses under changing climatic conditions. Members of the genus Streptomyces, long recognized for their exceptional capacity to produce secondary metabolites, have recently emerged as promising bioresources for enhancing plant tolerance to such stresses. Their metabolites include polyketides, phenazines, melanin-like pigments, siderophores, volatile organic compounds, and phytohormone analogs. Collectively, these compounds can improve plant performance by scavenging reactive oxygen species, supporting osmotic adjustment and ion regulation, and modulating hormonal signaling and root architecture. This review summarizes recent progress in understanding how Streptomyces-derived metabolites contribute to abiotic stress alleviation in plants, with emphasis on molecular mechanisms and rhizosphere ecology. Genomics and metabolomics studies further reveal extensive biosynthetic gene clusters with untapped potential for novel bioactive compounds. Evidence from major crops shows improved growth, antioxidant activity, and stress recovery following Streptomyces inoculation or metabolite application. However, key challenges remain, including linking specific metabolites to defined plant responses, standardizing assays, ensuring safety, and scaling production for field use. Integrating multi-omics, co-culture strategies, and formulation technologies will be essential to translate experimental findings into sustainable agricultural practice. Overall, Streptomyces secondary metabolites represent a promising frontier for environmentally sound solutions to abiotic stress in crops.