International Microbiology最新文献

A novel enrofloxacin-degrading fungus was isolated from a rhizosphere sediment of the submerged macrophyte Vallisneria spiralis L.. The isolate, designated KC0924g, was identified as a member of the genus Humicola based on morphological characteristics and tandem conserved sequence analysis. The optimal temperature and pH for enrofloxacin degradation by strain KC0924g were 28 °C and 9.0, respectively. Under such condition, 98.2% of enrofloxacin with an initial concentration of 1 mg L^-1 was degraded after 72 h of incubation, with nine possible degradation products identified. Four different metabolic pathways were proposed, which were initiated by cleavage of the piperazine moiety, hydroxylation of the aromatic ring, oxidative decarboxylation, or defluorination. In addition to enrofloxacin, strain KC0924g also degraded other fluoroquinolone antibiotics (ciprofloxacin, norfloxacin, and ofloxacin), malachite green (an illegal additive in aquaculture), and leucomalachite green. Pretreatment of cells of strain KC0924g with Cu²⁺ accelerated ENR degradation. Furthermore, it was speculated that a flavin-dependent monooxygenase was involved in ENR degradation, based on the increased transcriptional levels of these two genes after Cu²⁺ induction. This work enriches strain resources for enrofloxacin remediation and, more importantly, would facilitate studies on the molecular mechanism of ENR degradation with degradation-related transcriptome available.

Drug repurposing constitutes a strategy to combat antimicrobial resistance, by using agents with known safety, pharmacokinetics, and pharmacodynamics. Previous studies have implemented new fusidic acid (FA) front-loading-dose regimens, allowing higher serum levels than those achievable with ordinary doses. As susceptibility breakpoints are affected by serum level, we evaluated the repurposing of FA as an antimicrobial product against enterococci. FA minimum inhibitory concentrations (MICs) against standard enterococci strains; Enterococcus faecalis ATCC 29212 and Enterococcus faecium ATCC 27270 were 2 and 4 µg/mL, respectively. The MIC against 98 enterococcal clinical isolates was ≤ 8 µg/mL; all would be susceptible if categorized according to recalculated breakpoints (≥ 16 µg/mL), based on the serum level achieved using the front-loading regimen. FA administration in vivo, using the BALB/c mouse infection model, significantly reduced bacterial burden by two to three log₁₀ units in the liver and spleen of mice infected with vancomycin-susceptible and -resistant strains. Exposure of the standard enterococcal strains to increasing, but not fixed, FA concentrations resulted in resistant strains (MIC = 128 µg/mL), with thicker cell walls and slower growth rates. Only one mutation (M651I) was detected in the fusA gene of the resistant strain derived from serial passage of E. faecium ATCC 27270, which was retained in the revertant strain after passage in the FA-free medium. In conclusion, FA can be repurposed as an antimicrobial drug against enterococci with a low probability of mutational resistance development, and can be employed for treatment of infections attributable to vancomycin-resistant enterococci.

Previous research has confirmed the significant association between gut microbiota (GM) and male infertility (MI), but the causality between them remains unclear. This study aims to investigate the causal relationship between GM and MI using Mendelian randomization (MR) and provide supplementary information for the optimization of future randomized controlled trials (RCTs). Instrumental variables for 211 GM taxa were obtained from genome-wide association studies (GWAS), and inverse variance weighted (IVW) method was used as the main analysis method for two-sample MR analysis to assess the impact of GM on the risk of MI. Four methods were used to test for horizontal pleiotropy and heterogeneity of MR results to ensure the reliability of the MR findings. A total of 50 single-nucleotide polymorphisms (SNPs) closely related to GM were included, and ultimately identified 1 family and 4 general are causally associated with MI. Among them, Anaerotruncus (OR = 1.96, 95% CI 1.31-3.40, P = 0.016) is significantly associated with increased MI risk. Furthermore, we used four MR methods to evaluate the causality, and the results supported these findings. The leave-one-out analysis showed stable results with no instrumental variables exerting strong influence on the results. The causal direction indicated a positive effect, and the effects of heterogeneity and horizontal pleiotropy on the estimation of causal effect were minimized. We confirmed a causal relationship between GM taxa and MI, providing new insights into the mechanisms underlying GM-mediated MI.

The L-asparaginase (ASPN) enzyme has received recognition in various applications including acrylamide degradation in the food industry. The synthesis and application of thermostable ASPN enzymes is required for its use in the food sector, where thermostable enzymes can withstand high temperatures. To achieve this goal, the bacterium Bacillus subtilis was isolated from the hot springs of Tapovan for screening the production of thermostable ASPN enzyme. Thus, ASPN with a maximal specific enzymatic activity of 0.896 U/mg and a molecular weight of 66 kDa was produced from the isolated bacteria. The kinetic study of the enzyme yielded a Km value of 1.579 mM and a Vmax of 5.009 µM/min with thermostability up to 100 min at 75 °C. This may have had a positive indication for employing the enzyme to stop polyacrylamide from being produced. The current study has also been extended to investigate the interaction of native and mutated ASPN enzymes with acrylamide. This concluded that the M₁₀ (with 10 mutations) has the highest protein and thermal stability compared to the wild-type ASPN protein sequence. Therefore, in comparison to a normal ASPN and all other mutant ASPNs, M₁₀ is the most favorable mutation. This research has also demonstrated the usage of ASPN in food industrial applications.

Ten fungal species were isolated from soil in the Western Desert and Wadi El-Natron in Egypt. All fungal isolates were morphologically recognized down to the species level. Methanol extracts of fungal mycelia and ethyl acetate extracts of culture filtrate from the isolated fungi were evaluated for antimicrobial activity against six pathogenic bacteria and one pathogenic yeast (Candida albicans ATCC20231). Only ethyl acetate extracts of Fusarium circinatum, Aspergillus niger, and Aspergillus terreus culture filtrates showed significant antimicrobial activity against the majority of the investigated pathogens. The culture filtrate extract of Aspergillus niger exhibited notable cytotoxicity towards the breast cancer (MCF-7) cell line, with the lowest detected IC₅₀ recorded at 8 μg/μl. Whereas Fusarium circinatum and Aspergillus terreus had IC₅₀s of 15.91 μg/μl and 18 μg/μl, respectively. A gas chromatography-mass spectroscopy (GC-MS) investigation of A. niger's potent extract revealed 23 compounds with different biological activities. Glycidyleoleate was found to be the main extract component. Aspergillus niger extract was chosen to study its possible cytotoxic mechanism. The extract was found to induce apoptosis and cell cycle arrest at the < 2n stage. Despite a significant increase in caspases 8 and 9, the production levels of tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) have shown a significant decrease. The high interaction of glycidyleoleate against the studied cytokines' binding receptors was demonstrated via docking studies. In conclusion, the available data revealed that the culture filtrate extract of A. niger possesses promising antimicrobial, cytotoxic, and immunomodulatory properties.

The genus Halioglobus is one of the environmentally relevant members of the family Halieaceae, class Gammaproteobacteria. At present, the genus is composed of three validly published species. However, in the recent study of the family Halieaceae, the species Halioglobus pacificus was observed to branch outside of the main clade formed by the members of Halioglobus, suggesting its distinct taxonomic placement within the family. In the present study, the taxonomic placement of H. pacificus was reassessed using comparative genomics. Phylogenomic analysis revealed the paraphyletic relationship of H. pacificus with the type species of the genus Halioglobus, and further demonstrated its genus-level placement. This phylogenetic relationship was reinforced by the average nucleotide and amino acid identity values shared by H. pacificus with the members of the family Halieaceae. Moreover, the results of the pan-genome analysis, together with the phenotype data, further supported the exclusion of H. pacificus from the genus Halioglobus. Based on these findings, the species H. pacificus is thereby assigned to a new genus Parahalioglobus gen. nov. as Parahalioglobus pacificus comb. nov.

Background: The emergence of resistance in dermatophytes underscores the necessity for developing novel and alternative treatment options.

Methods: The present study aimed to evaluate the in vitro activity of nanoliposomal amphotericin B against a large panel of terbinafine-resistant Trichophyton indotineae isolates. In vitro susceptibility testing of nanoliposomal amphotericin B and comparators against 50 clinical isolates of terbinafine-resistant T. indotineae strains was performed by broth microdilution according to the Clinical and Laboratory Standards Institute (CLSI) M38-A3 document.

Results: The highest MIC₉₀ and widest MIC range were found for terbinafine (4 and ≥ 4 µg/ml) followed by itraconazole (0.5 and 0.016-16 µg/ml). In contrast, the nanoliposomal amphotericin B and conventional amphotericin B exhibited low MIC₉₀ (0.5 µg/ml) and MIC range (0.25-0.5 µg/ml).

Conclusions: The study findings revealed that nanoliposomal amphotericin B might be a promising candidate against terbinafine-resistant strains of T. indotineae. However, further studies are required to pave the way for developing novel antifungal compounds to combat fungal resistance.

A pigmented bioactive molecule from Streptomyces kunmingensis BS19 was isolated, characterized, and evaluated for anti-infective, antiproliferative, and wound-healing properties. The yellow-red pigment produced from the strain BS19 showed promising activity against methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium tuberculosis. Extracellular bioactive pigment from the strain BS19 was produced by agar surface fermentation and purified through bioassay guided preparative HPLC-based purification. Based on the results of UV, FT-IR, GC-MS, ¹H NMR, and ¹³C NMR spectral analyses, the purified pigment was identified as a chromopeptide class of molecule with phenoxazinone chromophore. Its molecular weight was determined as the chemical formula C₆₄H₉₀N₁₂O₁₆ and molecular weight 1283 g/mol. It exhibited promising antimicrobial activity against Staphylococcus aureus (ATCC 1720) and antiproliferative activity against 14 types of human cancer cell lines. It showed good in vivo wound-healing activity in the rat model. The present study explored Streptomyces kunmingensis as a newly added source for the isolation of chromopeptide antibiotics for antimicrobial, wound-healing, and anticancer applications.

A novel strain isolated from soil identified as Stenotrophomonas geniculata MK2 could control strawberries' postharvest disease gray mold. An in vitro investigation showed that MK2 had significant bioactivity against Botrytis cinerea, with an observed zone of inhibition of 85%. The strain MK2 was 88% effective in controlling gray mold on detached fruits. De novo whole genome sequencing analysis showed that strain MK2 has a single circular chromosome with a genome size of 736,465 bp, a G + C content of 66.34%, a coding ratio of 89.80%, and a protein-coding gene of 442. The NR database identified about 4284 genes among Stenotrophomonas spp. and S. geniculata, sharing the maximum number of 1277 genes with the MK2 strain. In COG annotation, most gene percentage was linked to general functions. In KEGG annotations, the majority of genes are associated with metabolism. According to the GO analysis, the maximum number of genes involved in the molecular process was linked to catalytic and transporter activity. CAZymes (carbohydrate-active enzymes) showed that enzymes related to glycosyl transferases (48), carbohydrate esterases (54), and glycoside hydrolases (51) are involved in the non-ribosomal synthesis of secondary metabolites. The PHI database showed that in strain MK2, the reduced virulence was 68 protein counts, and similarly unaffected pathogenicity protein counts were 52. AntiSMASH analysis for biosynthesis-related gene clusters involved in the production of secondary metabolites showed ten gene clusters coded for 2,3-dihydroxybenzoylserine, griseobactin, fuscachelin, benarthin, mirubactin, myxochelin, and bacillibactin. The MK2 strain could be a potent biocontrol agent for postharvest diseases.