Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology最新文献

Microbial inoculants show potential for remediating nitrate-rich, salinized soils. However, native strains often exhibit suboptimal performance under high-salinity and high-nitrate conditions, limiting their practical application. To develop a nitrate-reducing strain suitable for saline soil remediation, we adaptively acclimated a nitrate-reducing Bacillus velezensis strain BV-1 under high-nitrate conditions to enhance its salt tolerance and nitrogen metabolic capacity. The acclimatized strain exhibited significantly upregulated nar genes (4.71- to 7.56-fold) and nirD expression (1.36-fold), indicating enhanced nitrate assimilation and dissimilatory nitrate reduction to ammonium activity. In pot experiments, inoculation with this strain resulted in 46.85% nitrate removal, improved nutrient utilization (with increases of 21.86% in ammonium-N and 29.64% in available phosphorus utilization), and a 20.82% increase in lettuce fresh weight. These findings demonstrate that microbial acclimatization is an effective strategy for developing robust bioinoculants, with broad implications for sustainable agriculture and microbial strain engineering in salinized environments.

The COVID-19 pandemic affected the global healthcare delivery system, raising concerns about its influence on antimicrobial resistance (AMR). This systematic review and meta-analysis assessed the impact of the COVID-19 pandemic on the prevalence of MDR bacteria in different healthcare environments. A systematic search was carried out in PubMed-MEDLINE, Embase, Web of Science, BIOSIS, Scopus, and Google Scholar for articles published from December 2019 to January 2024. After screening 77 full-text studies, 28 studies were included in the analysis. The inclusion criteria included original human studies presenting MDR bacteria incidence before and during/after COVID-19 with reference to Carbapenem-resistant Acinetobacter baumannii, Carbapenem-resistant Enterobacteriaceae, Vancomycin Resistant Enterococci, Carbapenem-Resistant Pseudomonas aeruginosa, Methicillin-resistant Staphylococcus aureus, and Extended-Spectrum Beta-Lactamase-producing Enterobacteriaceae. The overall odds ratio (OR = 0.91, 95% CI: 0.70–1.17) indicates no significant change in the prevalence of multidrug-resistant (MDR) bacterial infection between the pre-COVID-19 and the COVID-19 period. There was no significant change in the prevalence of MRSA, ESBL, and VRE pre- and post-COVID. However, there was a significant reduction in the prevalence of CR-Ab, CRE, and CRPA pre- and during/after-COVID-19. MDR prevalence was significantly increased in Asia (18%) while it decreased slightly in North America (10.3%), showing variations in antibiotic use. The findings show that COVID-19 has different effects on the prevalence of MDR bacteria across geographical regions and healthcare facilities.

The anti-inflammatory, antioxidant properties of many probiotic microbes and their ability to modulate the composition of intestinal flora suggest that they have the potential to prevent and/or treat nonalcoholic fatty liver disease (NAFLD). The present study provides evidence that Lactiplantibacillus plantarum HP-B1280 can significantly reduce fat accumulation and inflammatory cell infiltration within the hepatocytes of fatty liver mice and thus may have potential application value in the prophylaxis and treatment of NAFLD disease. HP-B1280 also exhibits an extremely high level of resistance to acids and bile salts. The fermentation broth of HP-B1280 cultures is effectively suppresses the growth of a variety of common human pathogens. A comprehensive analysis of the complete genome sequence of L. plantarum HP-B1280 was conducted. Results indicated that the genome of L. plantarum HP-B1280 was devoid of resistance genes, drug resistance genes, as well as virulence factors. The annotation of the genome provides a foundation for further studies on the mechanism underlying the prevention and treatment of NAFLD by L. plantarum HP-B1280. In summary, the findings of the present study provides valuable insights into the potential use of probiotics, such as L. plantarum HP-B1280 in the amelioration and prophylaxis of NAFLD.

Cordyceps militaris is a rare and highly valued medicinal fungus that has attracted considerable attention due to its production of diverse bioactive compounds, including nucleosides such as cordycepin, polysaccharides, lovastatin, carotenoids, etc., all of which exhibit significant nutritional and therapeutic potential. However, the large-scale utilization of C. militaris is constrained by several critical challenges. A major limitation is the progressive degeneration of strains over successive subcultures, which adversely affects fruiting body formation and metabolite biosynthesis. Moreover, genetic instability during long-term culture, contamination risks in large-scale production, and the lack of standardized cultivation and extraction protocols often result in variable product quality. The absence of efficient genetic transformation systems and the low success rate of genome editing approaches further complicate efforts in molecular strain improvement. This review provides a comprehensive overview of the principal bioactive compounds produced by C. militaris and critically evaluates the current challenges and limitations associated with both conventional and advanced strain improvement strategies. These include conventional approaches such as mutagenesis and protoplast fusion, as well as genome-editing technologies like CRISPR/Cas9, which are employed to enhance the biosynthesis of target metabolites. Moreover, the integration of metabolic engineering frameworks offers significant potential for rational strain design, optimization of bioprocesses, and the discovery of novel therapeutic agents.

Graphical abstract

A novel uricase (urate oxidase; EC 1.7.3.3), produced in the absence of uric acid induction, was isolated and characterized from the bacterial strain IICT-RSP4 and identified through 16S rRNA sequencing and whole-genome analysis. Among the tested conditions, dextrose and urea were found to be the most effective carbon and nitrogen sources, respectively, for enhanced uricase production. Enzyme purification was performed via ammonium sulfate precipitation followed by size-exclusion chromatography coupled with Fast Protein Liquid Chromatography (FPLC). Molecular characterization of enzyme was performed by SDS–PAGE and ESI–LC–MS. The results showed that the uricase producing strain IICT-RSP4 was identified as Delftia tsuruhatensis IICT-RSP4. The highest enzymatic activity was achieved under optimal conditions of pH 7.0 and a temperature of 30 °C and calculated as 20.72 U/ml. The purification resulted an increase in enzyme activity from 1.7 to 40 U/ml and revealed a molecular weight of approximately 36 kDa. Biochemical profiling of enzyme indicated an optimal activity at pH 9.0 and 30 °C in the presence of cobalt ions. These findings suggest that D. tsuruhatensis IICT-RSP4 is a promising microbial source of uricase with potential biotechnological applications.

Group of Bacillus have high resilience capacity in harsh conditions, including in a heavy metal contamination environment. We isolated Bacillus altitudinis RDK4 from soil around an ex-mining area which showed lead-tolerant phenotype. In this study, the genomics of RDK4 was analyzed to identify genes or pathways potentially involved in lead-tolerant activity and was employed for evolutionary relationships analysis of this isolate towards other Bacillus species. Whole genome sequence of RDK4 was obtained by using Oxford Nanopore Technology platform. The genome size of RDK4 was 3,704,351 bp (3700 coding sequences), in circular form, with average GC% of 41.44%. Functional categories of RDK4 annotated genes resulted in four dominant categories included genetic information processing (13.6%), signalling and cellular process (11.0%), environmental information processing (9.6%) and carbohydrate metabolism (9.6%). Some pathways (complete modules) that are potentially involved in the lead-tolerant phenotype were identified, including the biosynthesis of biosurfactants (fengycin, lychensin), antioxidants (terpenes, polyketides), and siderophores (schizokinen). In addition, genetic properties of metal-efflux system (cadA, FieF) and exopolysaccharide-mediated metal sequestration (eps operon) and antioxidative response genes (katA, ahpC, TrxA, SodA/C) were also present in the RDK4 genome. Thus, the lead-tolerant phenotype is potentially the result of a combination of these modes of action. Comparative genome analysis revealed that as many as 1523 protein clusters were shared between RDK4 and other Bacillus species. Interestingly, RDK4 was found to be in a close evolutionary relationship with B. subtilis and B. megaterium, sharing 215 and 85 specific protein clusters, respectively. These findings highlight the genetic properties and lead-tolerance mechanisms of RDK4, which support its application as a bioremediation agent.

Polypropylene (PP) products are extensively utilized in both clinical and laboratory environments due to their advantageous physicochemical properties and cost-effectiveness. In this study, we investigated phenotypic alterations and oxidative stress responses of Pseudomonas aeruginosa (PA) under short-term PP exposure (24 h) through three experimental treatments: 0 mg/L PP (control), 10 mg/L PP (low concentration), and 1000 mg/L PP (high concentration). The results demonstrated that, compared to the control group, treatment with the low concentration and high concentration groups of PA led to enhanced resistance to four antibiotics: ciprofloxacin, imipenem, amikacin, and gentamicin. Biofilm formation increased by 45.68% and 140.93%, respectively, while pyocyanin production rose by 42.77% and 62.07%, respectively. At the same time, both swimming and twitching motilities were significantly enhanced. Furthermore, after treatment with the low- and high-concentration groups, the levels of H₂O₂ increased by 103.44% and 149.97%, respectively, malondialdehyde by 89.10% and 210.87%, and glutathione by 50.40% and 83.47%, respectively. Molecular dynamics simulations revealed that PP spontaneously formed a stable complex with the LasR receptor protein in PA through hydrogen bond interactions. The study concluded that under PP stress, PA exhibited enhanced resistance to certain antibiotics, altered phenotypic traits, and increased oxidative stress responses. These findings provide novel insights for public health strategies in preventing PA infections.

The microbial mineralization of struvite from high-salinity wastewater offers a promising approach for the simultaneous removal and recovery of phosphorus and nitrogen. Fish processing wastewater (FPW) is characterized by high organic pollutant loads, containing heavy metal copper ions, and variable salinity levels ranging from 2 to 21% NaCl. Such fluctuations in salinity can affect the efficiency of struvite biomineralization. The presence of heavy metal copper ions will also further restrict the function of the struvite-producing strains under high-salt conditions. This study focuses on screening microbial strains capable of producing struvite under high-salt stress and to investigate the impact of salt (NaCl) concentration on the treatment efficiency of synthetic FPW. Microorganisms were screened across a broad salinity range, and key parameters, including yield, pH, phosphate concentration, magnesium ion levels, and other indicators, were evaluated during the mineralization process. Furthermore, the ARTP mutagenesis technique was applied to identify mutant strains with enhanced copper ion tolerance and improved crystal production at 10% NaCl. A total of 54 microbial species were found to produce struvite while achieving elevated phosphorus (P) and magnesium (Mg) removal under 5% NaCl conditions. Among them, Halomonas olivaria MG-4 demonstrated broad salinity tolerance. Strain MG-4 exhibits a high recovery rate of P reaching 67% (p <  0.001) at 5% NaCl, and maintains 48–50% (p < 0.001) at 8–10% NaCl. Strain MG-4 exhibits a high recovery rate of P reaching 67% (p < 0.001) at 5% NaCl, and maintains 48–50% (p < 0.001) at 8–10% NaCl. The mutant strain MG-4(100 s-3) sustained high P and Mg removal and recovery efficiencies even at 8–10% NaCl in artificial wastewater systems. Compared with the wild-type MG-4, the mutant strain MG-4(100 s-3) exhibits enhanced tolerance to copper ions and significantly promotes struvite production at copper ion concentrations of 0.4–1.6 mM. These findings highlight valuable microbial resources for struvite biomineralization in FPW, offering potential for both efficient wastewater treatment and resource recovery.