International Microbiology最新文献

Pseudomonas aeruginosa is a multidrug-resistant (MDR) pathogen. It causes life-threatening diseases through quorum sensing (QS)-associated virulence. Thus, the attenuation of QS may be an effective strategy to combat the pathogen. In this study, Shewanella indica SU1 isolated from the marine environment showed QS inhibitory activity against biosensor strain Chromobacterium violaceum MTCC 2656. The lead compound was purified and tentatively identified as eicosyl heptafluorobutyrate (EPB). P. aeruginosa MCC 3457 was treated with EPB, and results revealed a reduced production of pyocyanin (79%), rhamnolipids (54%), exopolysaccharide (60%), and biofilm (66%). The motility was greatly affected in EPB-treated cultures. In an in silico approach, EPB exhibited good binding interactions and stability with the target protein LasR. The pharmacokinetics studies divulged that EPB, the lead compound, can be a good drug candidate. This is the first report on the QS inhibitory activity of S. indica SU1 and EPB as an anti-QS compound.

This study investigates the impact of a defined starter culture on the fermentation of cocoa beans and its influence on the production of volatile and non-volatile compounds related to sensory quality. A microbial consortium comprising Saccharomyces cerevisiae, Pichia kudriavzevii, Levilactobacillus brevis, and Acetobacter okinawensis was selected based on their enzymatic activity and acid regulation properties. Fermentation trials showed that the starter culture enhanced the synthesis of key volatile compounds, particularly esters and higher alcohols, such as 2-phenylethanol and 2-phenylethyl acetate, which contribute floral and fruity aromas. Compared to artisanal fermentation, treatments with starter cultures exhibited lower levels of lactic and acetic acids and an increase in succinic acid, indicating a balanced acid profile and potential metabolic synergy between inoculated and native microbiota. The study also identified specific volatile compounds as potential biochemical markers to monitor fermentation progress. These findings support the application of functional starter cultures to standardize and improve cocoa fermentation, offering opportunities to enhance quality and value in small-scale production systems.

An endophytic bacterium having the capability to produce biosurfactant was isolated from the root gall of Lady's finger (Abelmoschus esculentus). The stain reduces the surface tension of the culture media from 50.8mN to 30.8mN in 24 h and produces 3.3 g/L of biosurfactant at 48 h of incubation using glucose as a carbon source. It was revealed from the characterization of the biosurfactant that the strain produces a lipopeptide type of biosurfactant and the main component of the lipopeptide was surfactin. The bacterial strain was further characterized through molecular technique and identified as Providencia vermicola which was designated as strain SCL1. The biosurfactant produced by the strain was found to exhibit efficient antifungal activities against phytopathogenic fungi Colletotrichum gleoisporoides, Sclerotinium sclerotiorum, and Corynespora cassicolla. This is the first report that an endophytic bacterium Providencia vermicola can produce lipopeptide biosurfactant having antifungal properties against certain phytopathogenic fungi.

This research aimed to identify native biocontrol bacteria capable of suppressing Phytophthora infestans in potato crops. A total of forty bacterial strains were isolated from wheat (Triticum aestivum), sunflower (Helianthus annuus), potato (Solanum tuberosum), and cotton (Gossypium herbaceum) plants collected in Sibi, Pakistan. Out of these, ten isolates showed antagonistic effects against P. infestans, with inhibition percentages ranging from 27 to 62%. The isolate WL2.3 exhibited the strongest inhibition at 62%. Furthermore, sporangia germination tests, including those using cell-free supernatants, revealed that WL2.3 and its supernatant inhibited sporangia germination by 65% and 60%, respectively. Strain WL2.3 also showed various traits that promoted growth in plants, including solubility of phosphate, siderophores, ability to synthesize indole-3-acetic acid, cellulose lysis, and generation of hydrogen cyanide. The phylogenetic analysis based on 16S rRNA demonstrated a match of 98.80% with Bacillus subtilis with the GenBank accession number of PQ764123.1. The efficacy of WL2.3 was also experimented in pot experiments to determine its agronomic and pathological effects to potato plants infested with P. infestans. Of the 11 parameters that were considered, eight of them showed a significant improvement: percentage disease index, number of tubers, weight of tubers, length of the shoot, number of leaves, weight of roots, number of roots, and number of shoots. These results indicate that WL2.3 successfully reduced the effects of the oomycete pathogen, as shown by a decrease in the percentage disease index to 46% in the group treated with WL2.3. Thus, WL2.3 is a promising biocontrol agent for plant disease management and growth promotion.

Varroa destructor mite is a major threat to honeybee (Apis mellifera) populations, contributing to colony losses through parasitism and pathogen transmission. While extensive research has focused on Varroa biology and its role as a virus vector, its microbiome remains poorly understood, particularly regarding geographic variation. Here, we investigated the microbial diversity, composition, and functional potential of Varroa mite microbiota collected from two neighboring countries, Czechia and Slovakia. Using high-throughput sequencing and network analysis, we assessed alpha and beta diversity metrics, microbial co-occurrence patterns, and predicted metabolic functions. Our results revealed significant differences in microbial diversity between the two regions, with some bacterial taxa appearing more prevalent in specific populations. Network analysis suggested potential variation in the structural stability of microbial communities in Varroa mites, raising the possibility that geographic factors may influence microbial interactions. Functional profiling indicated region-associated differences in predicted metabolic pathways, possibly linked to certain bacterial taxa. While these findings provide new insights into the Varroa microbiome and its potential ecological role, the interpretation of geographic influence remains a subject of ongoing investigation to better understand its scope and underlying mechanisms. A deeper understanding of these microbial dynamics may contribute to the development of novel strategies for Varroa mite management and the conservation of honeybee health.

Unlike other Actinobacteria, Rhodococcus erythropolis PR4 contains three different copies of divIVA genes. The three divIVA genes show about 22-38% similarity with each other. Deletion mutants of the divIVA genes resulted in altered morphology: elongated cells in △divIVA-2 and short rod-shaped cells in △divIVA-1 and △divIVA-3. The expression of the divIVA-2 gene was found to be higher as compared to the divIVA-1 and divIVA-3 genes in wild-type cells. The subcellular localisation studies revealed that the three different DivIVA proteins are spatially present at different regions of cell space. Our results suggest that an interplay of the three DivIVA proteins plays a role in cell shape maintenance in R. erythropolis PR4. Bioinformatics analysis and interactome study show that amongst the three copies of divIVA genes, the second copy, i.e., divIVA-2 gene, might have a more governing function in the cell division process as compared to the other two copies.

Background: Given frequent dental restorations, understanding the interactions of probiotic Streptococcus dentisani with enamel and dental materials is key, in contrast to the well-studied Streptococcus mutans. This knowledge is vital for the potential applications in promoting oral health of S. dentisani.

Objective: This study aims to evaluate and compare S. mutans and S. dentisani initial adhesion, proliferation, and colonization on dental enamel and commonly used dental materials: nickel-chromium alloy, porcelain, lithium disilicate, autocured, and thermocured acrylics, using atomic force microscopy (AFM).

Methods: The study utilized S. mutans ATCC 35665 and S. dentisani CECT 7746 cultured in brain-heart infusion (BHI) broth. The dental substrates used consisted of enamel obtained from healthy unerupted third molars, nickel-chromium alloy (Ni-Cr), porcelain, lithium disilicate, and both autocured and thermocured acrylics. All simples were cut into 1 cm pieces and subsequently mounted for the AFM analysis. Bacterial suspensions were incubated on these surfaces for 24 h. Surface topography and bacterial adhesion, proliferation, and colonization were analyzed using AFM in contact mode. Roughness parameters (R_a, R_rms, R_Max) were quantified from AFM images using the Nanoscope analysis software.

Results: Atomic force microscopy analysis revealed that after a 24-h incubation, S. mutans demonstrated a superior capacity to adhere, proliferate, and colonize all tested substrates compared to S. dentisani. Streptococcus dentisani was found to be more susceptible to the bactericidal effects of the materials. Notably, porcelain and lithium disilicate surfaces exhibited strong antimicrobial activity. On porcelain, no intact S. dentisani cells were observed, only bacterial debris. Similarly, lithium disilicate showed evidence of bacterial decomposition for both strains, suggesting a potent bactericidal effect.

Conclusion: For the first time, our data revealed that S. dentisani exhibited a reduced capacity for dental surface adhesion, proliferation, and colonization across all tested substrates, compared to S. mutans.

The global emergence of multidrug-resistant Escherichia coli (MDR E. coli), driven by excessive antibiotic use and environmental persistence, poses a major threat to public health. Bacteriophages (phages) have garnered renewed interest as targeted biocontrol agents against such pathogens. In this study, we isolated and characterized two lytic phages, EC.W1-1 and EC.W15-3, specifically targeting diverse sequence types (STs) of MDR E. coli. Both phages belong to the family Straboviridae and genus Tequatrovirus. They demonstrated remarkable stability across pH 2-10 (4 h) and temperatures below 80 °C (1 h), and exhibited potent in vitro lytic activity at various multiplicities of infection (MOIs, 10-0.001). One-step growth curves revealed short latent periods (10-15 min) and moderate burst sizes (64-83 PFU/cell). Genome analysis showed sizes ranging from 37,736 to 123,792 bp, with G + C contents of 35.6%-37.2%, and no virulence or antibiotic resistance genes were detected, underscoring their safety profile. Functional annotation indicated coding sequences related to structural proteins, DNA replication, transcription, repair, and lytic functions. Importantly, the phages maintained partial activity in mouse and human serum and exhibited intracellular persistence in murine macrophages, supporting their biological stability. Notably, combined treatment of phages with sub-lethal antibiotic doses effectively inhibited extended-spectrum β-lactamase (ESBL)-producing and carbapenem-resistant E. coli (CREC). Moreover, both phages efficiently disrupted biofilms formed by different MDR E. coli STs. Collectively, these findings highlight the strong therapeutic potential of EC.W1-1 and EC.W15-3, offering a promising alternative or adjunct to antibiotics in combating MDR E. coli infections.

Melanin is a multifunctional biopolymer with a wide range of applications in biomedical, cosmetic, and environmental industries. While most melanin-producing bacteria are isolated from environmental sources, endophytic bacteria remain largely unexplored despite their metabolic adaptability and potential for high-yield production. This study investigates extracellular melanin biosynthesis by the endophytic bacterium Pseudomonas plecoglossicida SSSK-2, isolated from Neolamarckia cadamba. Melanin production was optimized in submerged culture using an Artificial Neural Network (ANN) linked with a Genetic Algorithm (GA), yielding 7.4 ± 0.39 g/L in seven days. The produced melanin was slightly soluble in water and exhibited a porous, irregular surface. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed the presence of functional groups, including NH, OH, COO⁻, CH₃, and CH₂. Its solubility profile, UV-Visible spectral properties, FTIR characteristics, resistance to kojic acid inhibition, and absence of the tyrosinase gene suggest the pigment is likely pyomelanin. It demonstrated a Sun Protection Factor (SPF) of 102.84 ± 6.13 at a concentration of 0.2 mg/mL. It also exhibited 71.8 ± 6.0% free radical scavenging activity at 80 µg/mL, which is slightly lower than the 77.12% activity of ascorbic acid at the same concentration. The highest chelating activity was 64.6 ± 1.67% at a concentration of 200 µg/mL. For anti-inflammatory activity, melanin showed 69.69 ± 1%, lower than the 82 ± 2% recorded for diclofenac sodium at 50 µg/mL. The cytotoxicity of melanin, determined through the brine shrimp nauplii assay, was 1121 µg/mL, exceeding the safe threshold of 1000 µg/mL. These findings suggest that melanin has promising applications in biomedicine, radioprotection, cosmetics, and bioremediation.