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

Three endophytic Sphingobium strains, WW5^T, 11R-BB, and HT1-2^T, were isolated from Salix sitchensis stems, Populus trichocarpa roots, and Pluchea carolinensis shoots, respectively, growing on nutrient-limited rock substrates undergoing primary succession. Cells are Gram-negative, strictly aerobic, rod-shaped, catalase-positive, and motile by a single flagellum. Colonies formed within 2–3 days on nitrogen-limited combined carbon medium (NLCCM) and mannitol-glutamate/Luria (MGL) media. Growth occurred at 25–35 °C (optimum 30–32.5 °C), pH 5–8, and up to 2% NaCl for strains WW5^T and 11R-BB and 3% for strain HT1-2^T. Cellular fatty acid profiles were dominated by C_18:1 ω7c and C_16:1 ω7c. The predominant respiratory quinone was ubiquinone-10, and the principal polar lipids were phosphatidylethanolamine, sphingoglycolipids, and phosphatidylglycerol. Hybrid genome assemblies ranged from 5.49–5.72 Mb with 64.0–64.2 mol% GC, and 5404–5635 coding sequences. The 16S rRNA gene sequences of strains WW5^T, 11R-BB, and HT-12^T showed 99.5–99.9% identity to S. yanoikuyae JCM 7371^T, but formed a separate lineage in neighbor-joining, maximum-likelihood, and maximum-parsimony trees. Pairwise digital DNA–DNA hybridization (dDDH; 99.8%), average nucleotide identity based on BLAST (ANIb; 99.98%), and alignment fraction (AF; 99.5%) indicate that strains WW5^T and 11R-BB are conspecific and represent the same subspecies. Strain HT1-2^T showed lower relatedness (70% dDDH; 95.05–95.31% ANIb; 76–79% AF) but was more closely related to strains WW5^T and 11R-BB than to S. yanoikuyae JCM 7371^T, supporting its placement as a subspecies within the same species as strains WW5^T and 11R-BB. Based on phylogenomic, genomic, and phenotypic evidence, these strains constitute a novel species, Sphingobium salicis sp. nov., with the strain WW5^T (DSM 120182^T, NCCB 101075^T) designated as the type strain.

This study aimed to investigate the diversity of Acinetobacter spp. isolated from aquatic environments along the Brazilian coast, with a focus on environmental reservoirs of clinically relevant resistance genes. Twenty-three Acinetobacter isolates were recovered from marine animals, floating plastic, and surface water samples collected in two contrasting Brazilian regions: the heavily polluted Guanabara Bay (Rio de Janeiro) and the pristine Fernando de Noronha Archipelago (Pernambuco). Seven species were identified, with A. venetianus (n = 13) and A. johnsonii (n = 4) being the most frequent. Two A. johnsonii isolates carried the metallo-β-lactamase gene blaNDM-1, along with resistance to fluoroquinolones and carbapenems. Resistance to polymyxins and aminoglycosides was also observed in A. haemolyticus, A. baumannii, and A. modestus. ApaI-PFGE dendrogram and phylogenetic analyses based on single nucleotide position (SNPs) revealed high genetic diversity, and global comparisons placed the environmental isolates in lineages distinct from those commonly associated with healthcare-associated infections. This study highlights the diversity of Acinetobacter spp. in aquatic environments and their potential role as reservoirs of clinically important resistance genes, including blaNDM-1. By uncovering resistance mechanisms in environmental Acinetobacter strains, this work reinforces the relevance of environmental surveillance for One Health initiatives, particularly in regions with significant anthropogenic impact.

Lactic acid bacteria (LAB) are known to possess potent antifungal activity; however, the factors that affect this activity remain poorly investigated. In this study, we explored the influence of physicochemical and nutritional factors on the antifungal activity of five LAB strains namely Lactiplantibacillus pentosus 22B, Leuconostoc mesenteroides 8C2, Lactiplantibacillus plantarum 21B, Enterococcus faecium LC2V5 and Enterococcus faecium LC2P8. These factors included incubation period, medium initial pH, incubation temperature, long-term storage and carbon source. Results showed that these factors significantly influenced the antifungal activity of the studied LAB strains (p < 0.0001). The optimal conditions yielding the most potent inhibition (21 ± 0.4 mm to 19 ± 0.4 mm) were identified. Specifically, maximum activity was achieved after a 48-h incubation (late stationary phase), at 25–30 °C, an initial pH of 3–4, and with sucrose, galactose, or mannose as the carbon source, depending on the strain. Moreover, long-term storage at − 80 °C led to complete loss of activity in two strains (8C2 and LC2P8), while the other three remained stable. Furthermore, HPLC and GC–MS analyses were used to identify the antifungal compounds produced by these three stable strains. The results revealed the presence of various organic acids (lactic, acetic, formic, malic, and fumaric acids) and fatty acids, such as 9-octadecenoic acid, 11-dodecenoic acid, 10-hydroxy. Scanning electron microscopy confirmed that these compounds caused significant structural damage to fungal mycelia, supporting their demonstrated fungicidal effects. This study improves our understanding of the key factors and mechanisms underlying LAB antifungal activity, contributing to the optimization of their use as natural antifungal agents.

Recent studies have established the gut microbiome as a crucial player in breast cancer diagnosis, progression, and treatment. Distinct microbial patterns have shown promise as non-invasive diagnostic and prognostic biomarkers, supporting patient stratification and risk assessment based on microbiota composition. The gut microbiome also modulates estrogen metabolism, influencing the risk of hormone receptor-positive breast cancer, while dysbiosis can promote chronic inflammation and tumor expansion. Moreover, accumulating evidence demonstrates that gut bacteria can alter responses to chemotherapy and immunotherapy, suggesting that microbiota modulation may enhance treatment efficacy. With the advent of omics technologies and machine learning, intricate host–microbe interactions are being decoded, revealing new molecular targets and therapeutic opportunities. Importantly, early clinical and interventional studies using probiotics, prebiotics, and fecal microbiota transplantation (FMT) are being explored to restore microbial balance, mitigate therapy-related side effects, and improve antitumor immunity in breast cancer patients. Together, these advances underscore the translational potential of microbiome research, paving the way for microbiota-guided diagnostic, prognostic, and therapeutic strategies in personalized breast cancer management.

Brazil is a global leader in grain production, with corn reaching 122 million tons in the 2024/2025 harvest. Pest control, particularly of Spodoptera frugiperda, depends heavily on cypermethrin, a Class II hazardous synthetic insecticide with significant environmental risks. This study assessed the tolerance and degradation capacity of Pseudomonas-affiliated strain and Burkholderia-like strain in cypermethrin-contaminated environments, along with their indole-3-acetic acid (IAA) production and impact on early maize development. Both strains tolerated the insecticide and grew at varying concentrations, with Burkholderia-like strain showing superior degradation potential at 25 mg L⁻¹. Microcosm respirometry indicated initial CO₂ reduction post-inoculation due to microbial competition, followed by increased CO₂ at 200 mg L⁻¹, suggesting cypermethrin use as a carbon source by adapted microbes. IAA production by Burkholderia-like strain remained high despite contamination, whereas Pseudomonas-affiliated strain showed delayed synthesis. Growth assays revealed that Burkholderia-like strain (UAGC867) promoted shoot development and dry biomass accumulation in maize seedlings under cypermethrin stress, an effect not observed for Pseudomonas-affiliated strain. These findings highlight the potential of Burkholderia-like strain for bioremediation and plant growth promotion in insecticide-impacted agricultural systems, offering a sustainable approach to enhance productivity while reducing environmental harm.

Xylanases are used in a wide range of applications such as food, feed, and bioenergy production. Many industrial applications need to be carried out at high temperatures, so it is important to discover new thermophilic xylanases. In this study, a xylanase gene (576 bp), denominated apxyn11a, was obtained from Allostreptomyces psammosilenae YIM DR4008^T and was cloned and heterologously expressed in Escherichia coli BL21(DE3). The recombinant xylanase (ApXyn11A) was isolated and purified by Ni²⁺-affinity chromatography. The molecular weight of recombinant ApXyn11A was 22.7 kDa. Its optimum reaction temperature and pH were 65 °C and 5.6, respectively. It maintained above 95% relative activity after incubation at 55 °C for 120 min and more than 80% residual activity after incubation in pH 4.0–6.0 for 24 h. What more, ApXyn11A exhibited more than 60% relative activity in presence of 3.5 M NaCl. The kinetic parameters K_m (0.2 mg/mL), V_max (2000 μmol/min/mg) and K_cat (755.09 S⁻¹) were determined using corn cob xylan as the substrate. These indicate that ApXyn11A has the properties of small molecular weight, thermophilic, salt and acid tolerance, which predicts the potential use of ApXyn11A in food, feed, paper and bioenergy fields.

Vannamei shrimp is a promising aquaculture commodity, but presence of Vibrio parahaemolyticus bacteria in cultivation poses a challenge to increasing productivity. Quorum sensing allows bacteria to regulate pathogenicity based on population density. The aim of this study were to screen antiquorum sensing agents that can inhibit bacterial communication, thereby reducing pathogen virulence. The method used in the screening process goes through several stages, such as isolation of anemone symbiont bacteria, screening for inhibition of violacein and antibiofilm production, as well as molecular identification of potential isolates. The highest inhibition of visualization of violacein (diameter of non-purple zone) was shown by SG03 (28.00 mm). Based on the analysis of the inhibition percentage of violacein production and the percentage inhibition of biofilm formation from 105 isolates obtained from 3 species of sea anemones, there are six isolates with inhibition percentage values above 80%, namely HM12, HM19, EQ30, SG03, HM05, and EQ05. Based on 16s RNA identification, six potential isolates were identified as Schouchella sp., Shewanella sp., Halobacillus sp., Pseudomonas sp., Micrococcus sp., and Psychrobacter sp., respectively. Based on whole genome analysis (WGS), isolate HM19 detected the AHL acylase gene (PvdQ), EQ 05 detected the AHL lactonase gene (aiiA), and isolate SG 03 detected the aiiA and PvdQ genes. Six isolates of anemone symbionts have been identified that show the ability to produce anti-quorum sensing agents. This provides potential for effective and environmentally friendly control of pathogenic bacteria.

We investigated the oscillatory expansion of Bacillus subtilis biofilms on minimal salts glycerol glutamate (MSgg) agar by modulating the concentration of the nutrient glutamate and the rigidity of the surface via agar concentration. The concentration of glutamate and agar influenced the parameters of biofilm oscillation. Specifically, elevated glutamate levels boosted the initial growth rate (within the first 15 h) and prolonged the oscillation period. Conversely, increasing the agar concentration physically restrained colony expansion and dampened the amplitude of growth rate variations, leading to a more uniform, yet oscillatory, progression. Beyond altering the physicochemical environment, we probed the biofilm under competitive condition; the oscillatory period lengthened and resulted in asymmetric colony morphology. Furthermore, during self-healing following mechanical disruption, the oscillatory pattern was intact; the biofilm regenerated, with rapid recovery at the colony edges than at the center. To validate these experimental observations, we developed a spatial-temporal model of biofilm metabolism. This computational model successfully simulated the oscillatory growth on solid surfaces. It confirmed that the interplay between localized nutrient availability and the development of physical heterogeneity in biofilm thickness is a fundamental driver of the oscillatory patterns observed in B. subtilis biofilms, providing a unified theoretical basis for our empirical findings.

Graphical abstract

Chromobacterium subtsugae is the only species in this genus exploited for biological pest control. In this study, we demonstrated the insecticidal properties of Chromobacterium piscinae ESALQ6200 against Dalbulus maidis, even at low concentrations, using treatments with only bacterial cells and cell-free filtered supernatant containing secreted metabolites. Notably, we did not observe increased mortality with higher concentrations of C. piscinae ESALQ6200 cells (3.5 × 10⁴ to 6.7 × 10⁹ cells/mL) or cell-free filtered supernatant (1%, 25%, 100%). Mortality rates observed in the cell treatments were 76.9% (6.7 × 10⁹ cells/mL), 75.2% (6.81 × 10⁷ cells/mL), 78.7% (5.14 × 10⁶ cells/mL), 77% (5.03 × 10⁵ cells/mL), and 74.5% (3.55 × 10⁴ cells/mL), while in the cell-free filtered supernatant treatments mortality rates were 72.9% (100%), 65.8% (25%), and 67% (1%). We believe these results may relate to effects on pest behavior, feeding inhibition, or quorum sensing in regulating virulence factors. Genomic analysis revealed several potential virulence factors, including chitinases, biosynthetic gene clusters associated with hydrogen cyanide and violacein production, and two pore-forming toxins. The digital DNA–DNA hybridization analysis indicated a high sequence identity of 96.7% between ESALQ6200 and C. piscinae (ASM2108337), well above the 70% threshold commonly applied for prokaryotic species delineation. In contrast, ESALQ6200 showed significant divergence from other Chromobacterium reference genomes, with only 51.8% sequence identity to C. subtsugae (ASM3632055). Additionally, we identified type three and six secretion systems commonly associated with virulence in various bacterial species. Our findings support the application of C. piscinae ESALQ6200 in the biological control of corn leafhoppers. Furthermore, the identification of novel Chromobacterium toxins and metabolites may facilitate the development of innovative transgenic approaches to address pest resistance to B. thuringiensis.

A Gram-staining-negative, aerobic, red-pigmented, motile with a single polar flagellum and rod-shaped bacterium, designated HNIBRBA332^T, was isolated from an aquaculture seawater sample. Phylogenetic analysis based 16S rRNA gene sequences revealed that strain HNIBRBA332^T belonged to the genus Hahella of the family Hahellaceae and shared 95.3–99.9% sequence similarities with Hahella species. Whole genome sequencing of strain HNIBRBA332^T revealed the genome size of 7.2Mbp and the G+C content of 59.5%. The HNIBRBA332^T genome shared 89.0% of average nucleotide identity and 36.6% of digital DNA-DNA hybridization values to the genome of Hahella chejuensis KCTC 2396^T, the type species of the genus. Genes involved in prodigiosin biosynthesis were identified in the genome. The strain contained C_17:0 10-methly, summed feature 3 (C_16:1 ω7c and/or C_16:1 ω6c), C_18:1 ω9c and C_20:4 ω6,9,12,15c as the major fatty acids and menaquinone-7 as the major respiratory quinone. The major polar lipids were phosphatidylglycerol, phosphatidylethanolamine, and two unidentified aminolipids. On the basis of phylogenetic and phenotypic characteristics, strain HNIBRBA332^T is considered to represent a novel species of the genus Hahella, for which the name Hahella aquimaris (type strain HNIBRBA332^T) sp. nov., is proposed.