Applied Biochemistry and Microbiology最新文献

New derivatives of phosphonium salts (Z)-(2-(2-hydroxy-5-chlorphenyl)-2-phenylethenyl)octyldiphenylphosphonium chloride (PP8) and (2-hydroxybenzyl)dodecyldiphenylphosphonium chloride (6.5) were found to cause depolarization and permeabilization of the bacterial membrane. The ability of phosphonium salts to prevent the formation of Staphylococcus aureus biofilms and to disrupt them was demonstrated. Furthermore, the results demonstrated that the substances do not cause the development of resistance in the S. aureus strain. Finally, compound PP8 did not demonstrate mutagenic properties in the Ames test using strains of Salmonella typhimurium TA100 and S. typhimurium TA98.

In the present study, a comparative analysis of the probiotic properties of L. helveticus isolates obtained from kefir grains, a complex consortium of bacteria and yeasts used in the production of kefir (strains KF4, KF5, and KF6), and mammalian feces (KF7, NK1, and H9) was performed. At the genetic level, all the strains studied had the potential to form biologically active peptides, assimilate various sugars, and exhibit antimicrobial activity, which was also confirmed in vitro.

Currently, environmentally friendly processes for processing raw materials containing rare earth elements (REEs) are being actively developed. Microorganisms play an important role in the biogeochemistry of REEs, but the nature of the interaction of micromycetes with REEs remains poorly understood. This study examines the potential of extracting REEs from their insoluble forms using microscopic fungi. Using the example of the soil micromycete Aspergillus niger, the possibility of converting poorly soluble neodymium oxide Nd₂O₃ into water- and alcohol-soluble (ethyl and isopropyl) neodymium compounds is shown. The morphology and structure of A. niger cells and the distribution of insoluble and soluble forms of this rare earth element before and after bioleaching were studied using scanning electron microscopy (SEM). Bioleaching by micromycetes was modeled using the direct contact method. X-ray fluorescence analysis of extracts after bioleaching showed the presence of neodymium. These studies will help unlock the potential of microscopic fungi for their application in an environmentally friendly technology for the extraction of REEs based on bioleaching. This may serve as a basis for the development of an environmentally friendly alternative to the methods employed currently, which use strong inorganic acids or toxic substances.

Antibacterial resistance, particularly involving methicillin-resistant Staphylococcus aureus (MRSA), poses a significant challenge to global healthcare. This study investigates the synergistic effects of a polyphenolic mixture of curcumin (C) and quercetin (Q), (QC) combined with ciprofloxacin (CIP) to evaluate their antibacterial and antiproliferative potential in vitro. Minimum inhibitory concentrations (MICs) of CIP, C, and Q against MRSA were determined using the broth microdilution method. Synergistic interactions between QC and CIP were assessed through the checkerboard assay, while the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay evaluated cell viability in human colorectal carcinoma HCT-116 cancer cells treated with the combinations. The degree of synergism was calculated using the Chou-Talalay method and expressed as a combination index. The MICs were 9.8 ng/mL for CIP, 15.500 ng/mL for C, and 7.750 ng/mL for Q. A strong synergistic effect was observed with a fractional inhibitory concentration index (ΣFICI) of 0.3125, resulting in 16-fold reduction in the MIC of CIP when combined with QC (23.44 ng/mL QC and 0.61 ng/mL CIP). Additionally, the QC-CIP combination significantly enhanced antiproliferative effects, reducing the IC50 in HCT-116 cells by 12-fold compared to monotherapies. These findings suggest that the QC-CIP combination holds potential as an effective strategy to combat MRSA infections and inhibit cancer cell proliferation. Future in vivo studies are warranted to confirm its clinical applicability.

Rotavirus is the main cause of acute diarrhea in children under 5 years old. Due to acute disease, diagnosis needs to be made at the point of care, even in low-resource settings. Furthermore, rotavirus has many circulating genotypes. Therefore, we aimed to develop a rapid test for rotavirus detection using polyclonal antibodies. The optimal conditions for generating the test strip were investigated. The detection antibody was conjugated to gold nanoparticles (20 nm in diameter) at pH of 9.0 and concentration of 100 mg/mL. The capture antibody was sprayed at the T-line of the nitrocellulose membrane at a amount of 12 μg/cm. The properties of the developed test strip were also evaluated. The test result was shown in 10–15 min. The detection limit of the test strip was determined to be as low as 5 × 10⁴ CFU/mL by a strip reader and 10⁶ CFU/mL by naked eyes. The test strip did not cross-react with 18 different potential interfering pathogens. Interestingly, the test strip can detect 5 predominant circulating rotavirus genotypes. The sensitivity and specificity of the test strip were evaluated by testing with 665 clinical samples and reached 95.26 and 99.51%, respectively. The Kappa statistics showed k-coefficient of 0.955, indicating a very good agreement between the developed test strip and ELISA results. From the findings, the developed test strip can be used for point-of-care rapid detection of rotavirus in fecal samples. This investigation can be considered the first work applying polyclonal antibodies for the development of a lateral flow immunoassay test strip to detect human rotavirus.

This work aims to isolate and screen the fungicidal endophytic bacterial strains for biocontrol efficacy against Phytophthora palmivora, a soil-borne pathogenic fungus that kills durian trees worldwide. Among more than 100 isolates, 6 strains were screened as potential fungicidal strains with inhibitory efficiency of 67.4–79.8%. Based on 16S rRNA gene sequencing and phylogenetic analysis, these strains were identified as Bacillus amyloliquefaciens EB.CK9, Bacillus methylotrophicus EB.EH34, Bacillus amyloliquefaciens EB.EH18, Bacillus siamensis EB.KN10, Bacillus velezensis EB.KN15 and Paenibacillus polymyxa EB.KN35. In greenhouse tests, the two strains P. polymyxa EB.KN35 and B. velezensis EB.KN15 significantly reduced the damage to diseased roots by P. palmivora (33.3 and 35.6%, respectively), increased the rate of survival of durian trees (only 20.8 and 22.9% plant death, respectively), and showed a positive effect on promoting durian plant growth. Notably, the potential fungicidal effect of last two strains against P. palmivora was recorded for the first time in this work. HPLC analysis showed that these strains can secret several plant growth-promoting compounds, including gibberellic acid (GA3), indole-3-acetic acid (IAA), kinetin, and zeatin. Of these, GA3 and zeatin were produced with a significant amount by both strains. The volatiles bio-synthesized by these isolates were also identified using GC-MS analysis, and some major volatiles were found as fungicidal agents. This study suggested that P. polymyxa EB.KN35 and B. velezensis EB.KN15 may be potential biocontrol candidates for durian P. palmivora and bio-fertilizers for the sustainable production of durian crops.

Proteolysis, the process by which proteins are broken down into smaller polypeptides or single amino acids, is catalyzed by enzymes known as proteases. In this study, bacteria isolated from marine sediments were screened for protease production on skim milk agar medium. Out of 8 isolates, VITSDPB8 exhibited distinct zones of hydrolysis around its colonies indicating higher protease activity. This strain was closely related to Rossellomorea aquimaris. The enzyme activity was optimized by varying pH, temperature, and carbon and nitrogen sources. Enhanced protease activity (277 U/mL/min) was achieved under the optimized conditions: glucose as the carbon source, skim milk as the nitrogen source, pH 9.0, and a temperature of 42°C. The protease was extracted and subsequently purified, with the molecular weight of the purified enzyme determined to be approximately 45 kDa. The efficacy of the enzyme was evaluated for various applications. When applied as a purified extract, it successfully removed blood stains within 20 min. Additionally, after 60 min of incubation, the enzyme thoroughly digested the blood clots. The enzyme extract also exhibited notable antimicrobial activity against Salmonella typhi and Klebsiella pneumonia. These findings demonstrate that R. aquimaris VITSDPB8 has significant potential for protease production. This enzyme is promising bioactive compound for use in the medicinal applications.

Defensins are a class of antimicrobial peptides with antiviral, antibacterial, and biomodulatory activities [1, 2]. They present the effector molecules of the innate immune system and play an important role in host defence against pathogens, including enveloped or non-enveloped viruses, fungi and bacteria [3]. Defensins play an important role in virus invasion and infection. Here, we systematically describe the antiviral effects of defensins from four aspects: polypeptide structure, distribution in animals and antiviral mechanisms and applications emphasizing the potential of defensins as antiviral drugs.

(R)-citronellal is a key intermediate in the synthesis of L-menthol, one of the world’s three most important spices. It can be obtained by asymmetric reduction of (E/Z)-citral using old yellow enzymes (OYEs), but catalysis by the wild-type enzyme suffers from poor enantioselectivity as well as low efficient conversion. A protein-directed evolution technique was used to enhance the activity and enantioselectivity of CtOYE from Chroococcidiopsis thermalis. Upon the sequence alignment and molecular docking results, two amino acid residues at positions 103 and 351 were selected as saturation mutation sites. Finally, three single substitution variants of CtOYE-W103E, CtOYE-W103M, CtOYE-W103P with improved enantioselectivity (ee > 99%) and moderate conversion (>71%), and one double substitution variant CtOYE-Y351Q/W103E with high enantioselectivity (ee > 99%) and high conversion (83.2%) for reduction of (E/Z)-citral were obtained.

Strawberry, a hybrid fruit crop is threatened by wilt disease incited due to Fusarium oxysporum leading to significant yield loss, up to 40% in the recent decades. Management with soil drenching of fungicide (carbendazim) is a usual and regular practice whereas it causes negative impact on soil, water and environment. Thus, eco-friendly management by using potential biocontrol strains, namely Chaetomium globosum (Cg-6 and Cg-40) and Bacillus subtilis (Bbv-57), were employed for in vitro and in vivo studies. Under in vitro, Cg-6, Cg-40 and Bbv-57 were found to inhibit F. oxysporum by 55.6, 61.9 and 36.7%. In the experiment, activation of secondary metabolites by di-trophic interaction between F. oxysporum and each bio-control organism was confirmed and analyzed by GC-MS. The results showed that the presence of compounds like 3,4-dimethyl-1-dimethylsilyloxycyclohexane, 1,2-15,16-diepoxyhexadecane and cyclohexane in all the di-trophic interaction indicates the enzyme inhibitory, cytotoxic and antimicrobial activities. Further, the efficacy of these three biocontrol agents against the wilt disease was evaluated under field conditions on two different locations (protected and open field conditions). In this connection, liquid formulation of Cg-6, Cg-40 and Bbv-57 was developed and applied as basal (5 mL/kg of farm yard manure, seedling dip (5 mL/L) and soil drenching (5 mL/L) at monthly intervals. The treatments were applied as individual and in combination with vesicular arbuscular mycorrhiza (VAM) which was applied as basal dose. Among the different treatments, combined application of Cg-40 along with VAM as basal in both field trails recorded lesser wilt incidence with increased plant growth traits (plant height, leaves and flowers) and quality fruit yield.