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

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.

Two aerobic bacterial isolates, designated as strains CA2-7^T and CA1UV-4^T, were isolated from soil samples collected at a construction site in Cheonan. Both strains were identified as Gram-stain-negative, rod-shaped and a phylogenetic analysis based on 16S rRNA gene sequences indicated that these strains constitute a distinct lineage within the family Hymenobacter (order Cytophagales, class Cytophagia). The closest genetic relatives were found to be members of the genus Hymenobacter, specifically Hymenobacter ginkgonis HMF4947^T (with 16S rRNA gene sequence similarity of 97.28%) and Hymenobacter segetis S7-3-11^T (98.10%). Both strains grew optimally at pH 7.0, 25 °C, without NaCl. Fatty acid analysis revealed distinctive profiles, with C_15:0 anteiso and C_15:0 iso predominating in strain CA2-7^T, while C_15:0 iso and summed feature 3 (C_16:1 ω7c/C_16:1 ω6c) were the primary fatty acids in strain CA1UV-4^T. Both strains exhibited MK-7 as the major respiratory quinone. Biochemical, chemotaxonomic, and phylogenetic data support CA2-7^T and CA1UV-4^T as new Hymenobacter species. Accordingly, we suggest the names Hymenobacter cheonanensis and Hymenobacter convexus for strains CA2-7^T (= KCTC 92968^T = NBRC 116577^T) and CA1UV-4^T (= KCTC 92970^T = NBRC 116576^T), respectively.

Pseudomonas gelidaquae IB20^T is a rod-shaped, motile bacterium distinguished by the presence of multiple polar flagella. The average nucleotide identity (ANIb) and average amino acid identity (AAI) values between P. gelidaquae IB20^T and its closest phylogenetic relatives were all below the 95–96% thresholds currently accepted for delineating a novel species. Pseudomonas antarctica CMS 35 ^T displayed the highest ANIb and AAI values, at 92.67% and 95.98%, respectively. A distinctive feature of the P. gelidaquae IB20^T genome is the presence of a Type III Secretion System (T3SS), which is absent in the genomes of all closely related strains, making it the first Pseudomonas species isolated from Antarctica to carry this virulence system. Notably, we identified a novel candidate effector protein encoded within the T3SS gene cluster of P. gelidaquae IB20^T, exhibiting similarity to VopS T3SS effector proteins, which are predominantly found in Vibrio species. A comprehensive search of publicly available databases confirmed that this candidate effector protein is not present in any other Pseudomonas genome. Additionally, chemotaxonomic analysis showed that the dominant cellular fatty acids include summed feature 3 (C16:1ω7c/C15:0 iso 2-OH), C16:0, and C18:1ω7c. Based on extensive phenotypic and genotypic evidence, we propose that strain IB20^T represents a novel species within the genus Pseudomonas, for which the name P. gelidaquae sp. nov. is proposed, with IB20 designated as the type strain.

Corrinoid-dependent enzymes either catalyze methyltransfer reactions, or they generate substrate radicals using adenosylcobalamin for subsequent rearrangement reactions. The corrinoid-dependent methyltransferases are present in all domains of life and assumed to be exclusive for methyl-groups. In Methanosarcina, however, trace ethane production from ethanol has been shown in vivo, which led to the hypothesis that corrinoid-dependent methanol-specific methyltransferases are promiscuous towards also accepting ethyl-groups. Here, we show that the conversion of ethanol to trace amounts of ethane in Methanosarcina acetivorans involves homologous reactions of the known methanol-to-methane metabolism. The methanol methyltransferase (MtaB) activates ethanol and loads the ethyl-group onto the corrinoid-containing methyl-accepting protein (MtaC). Besides MtaCB, substrate promiscuity in corrinoid:coenzyme M methyltransferase (MtaA) and methyl-coenzyme M reductase (Mcr) are required to grant the microbe the capacity for ethane production. We show that the MtaCB subunits of M. acetivorans can activate ethanol, however, the ethane yields compared to methane are ca. 3 orders of magnitude lower. The ethyl-transfer capability was confirmed for each of the three MtaCB isozyme by quantifying the amount of ethane produced by mtaCB double deletion strains during growth in ethanol-supplemented media and in resting-cell suspensions. Ethane formation requires the cells to be grown on methanol to trigger the expression of the mtaCB genes, and detectable ethane formation starts only after all methanol has been consumed. Demonstrating that corrinoid-dependent methanol-specific methyltransferases process ethyl groups extends the pool of reactions to be considered in metabolic networks and suggests possible routes for biogenic ethane in nature.

Bacillus cereus is a significant foodborne pathogen whose infection can trigger gastrointestinal symptoms or systemic diseases in hosts, with severe cases potentially leading to sepsis or even death. In recent years, the misuse of antibiotics has led to varying degrees of drug resistance in foodborne pathogens, making the development of novel antimicrobial agents an urgent necessity. Natural active substances have become a focal point of current research due to their broad-spectrum and highly efficient antibacterial capabilities against foodborne pathogens. Prodigiosin (PG), initially garnering widespread attention in the pharmaceutical field for its multifunctional bioactivities, also demonstrates significant potential in the food industry. However, there is currently no reported research on the antibacterial effects of PG against B. cereus, its anti-infection mechanisms, and its impact on the host's intestinal microbiota. Based on this, our study focuses on PG as the research subject and B. cereus as the test strain, systematically investigating its therapeutic effect in B. cereus-infected mice. Additionally, we employed 16S rRNA-based microbiota analysis and metabolomics approaches to explore the effects of PG on the composition of the gut microbiota and metabolomic profiles. Collectively, PG exerts its therapeutic effects in B. cereus-infected mice by alleviating tissue damage, reducing inflammation, and modulating the abundance and diversity of the intestinal microbiota. These results highlight a novel strategy for alleviating B. cereus infections.