Journal of Applied Microbiology最新文献

Aims: Thecaphora frezzii, the causal agent of peanut smut, causes significant grain losses in Argentina. Current control strategies are insufficient to manage this pathogen. We investigate the effect of antioxidants on the in vitro development of T. frezzii hyphae, to identify compounds with antifungal activity, also evaluate protein and lipid profiles as potential targets for these compounds.

Methods and results: The antifungal activity was evaluated in both, solid and liquid media, and minimum inhibitory concentration and minimum fungicidal concentration were calculated. The protein profile was assessed using sodium dodecyl sulfate polyacrylamide gel electrophoresis, while lipids were analyzed by thin-layer chromatography (TLC) and gas chromatography with flame ionization detection, both before and after hyphal treatment. Lipase activity was analyzed using agar Tween 20 and TLC, while lipid peroxidation was evaluated by the thiobarbituric acid-reactive substance (TBARS)assay. Microscopy was used to observe morphological and metabolic changes. Butylated hydroxyanisole, methylparaben, and lipoic acid showed inhibitory effects on T. frezzii. Lipoic acid was chosen for further study due to its lack of environmental toxicity. Lipoic acid induced the loss of cytosolic proteins, hydrolysis of triglycerides, and increased levels of free fatty acids, monoacylglycerols, and diacylglycerols. It also caused a decrease in ergosterol levels and alterations in the fungal cell wall and membrane, ultimately leading to cell death.

Conclusions: This study demonstrates the efficacy of lipoic acid in inhibiting the in vitro development of T. frezzii.

Aims: This study investigated occurrence of Salmonella in faecal sludge from public toilets in Nigeria and genetic relatedness of strains that have been reported to cause human infection across Africa.

Methods and results: The study collected 150 human sludge from public toilets and identified Salmonella through culture and PCR. Isolates were tested for antimicrobial susceptibility and sequenced using Illumina MiSeq. Draft sequences were compared with sequence data from Enterobase and GenBank. Twenty-four (16.0%) of sewage samples were positive for Salmonella [CI95 (10.2-21.8)]. Salmonella serotype Give [sequence type (ST) 516], Salmonella serotype Seftenberg (ST-14), and Salmonella serotype Chester (ST-411) were the most prevalent serovars found in 45.8%, 16.7%, and 16.7% of samples, respectively. Most of the isolates were sensitive to the antimicrobials tested, only one isolate of Salmonella serotype Derby showed resistance to ampicillin and cefazolin. Notably, 91.7% of the strains had the aac (6)-Iaa gene and point mutations in parC, gyrA, and acrB. Salmonella serotype Chester showed genetic relatedness with strains from Benin Republic and South Africa.

Conclusions: There is genetic relatedness of present strains and those associated with human infections in Africa.

Aims: Drought is one of the most destructive abiotic factors for agricultural production, causing considerable yield losses. Quinoa (Chenopodium quinoa Willd.) is cultivated worldwide in different environmental conditions due to its nutritional characteristics and ability to grow in harsh environments. This study aims to select drought stress tolerant rhizosphere bacteria from the Bolivian altiplano to evaluate their quinoa growth-promoting capacity, including in vitro germination, seedling growth under drought stress in greenhouse conditions and field studies.

Methods and results: Rhizosphere soil from the southern highlands of Bolivia was collected to isolate 164 drought-stress tolerant bacteria. From these, 28 strains were shown to produce indole acetic acid, and/or to possess nitrogen-fixing or phosphate solubilizing capacity under in vitro conditions. Furthermore, all strains were evaluated for improvement of in vitro quinoa seed germination. Based on these properties, nine bacterial strains were formulated in three different matrixes and evaluated for quinoa seedling growth promotion during drought stress in a 3-month greenhouse experiment. Three strains were shown to significantly (P < 0.05) increase root length of the quinoa seedlings. One strain was selected and shown to significantly (P < 0.05) increase leaf number in a field trial under semi-arid conditions in the southern altiplano in Bolivia. DNA sequencing and phylogenetic analyses of the 16S locus putatively identified the three strains with growth-promoting potential under drought stress as members of the genera Bacillus, Pseudomonas, and Serratia.

Conclusion: Microorganisms from the arid Bolivian altiplano constitute a potential biological source of bioinoculants to improve quinoa productivity and provide sustainable mitigation of climate change effects.

Aims: The main objective of this study was to produce erythronolide B (EB) and 3-O-α-mycarosylerythronolide B (MEB) in Streptomyces coelicolor and enhance the MEB production by expressing the glucose-1-phosphate thymidylyltransferase (RfbA).

Methods and results: We expressed eryF and eryB genes (eryBII, eryBIII, eryBIV, eryBV, eryBVI, and eryBVII) to produce EB and MEB. The expression was confirmed by quantitative real-time polymerase chain reaction. Furthermore, the MEB's production was improved by more than 100-fold by expressing an enzyme, RfbA, which is absent from the erythromycin gene cluster, to promote the biosynthesis of TDP-L-mycarose. We discuss the feasibility of alternative Streptomyces species for erythromycin production based on the presence or absence of RfbA.

Conclusions: The RbfA enzyme from Saccharopolyspora erythraea was expressed in S. coelicolor M1152 along with the MEB biosynthesis pathway, resulting in a large increase in MEB production (>100-fold).

Aims: Rice blast, caused by Magnaporthe oryzae, is one of the most devastating diseases of rice (Oryza sativa L.). The aim of this study was to investigate the biocontrol potential of rice rhizosphere actinomycetes against M. oryzae Guy 11, and elucidate the antagonistic mechanisms.

Methods and results: An isolate characterized as a Streptomyces corchorusii strain (Sc75) using the 16S rRNA gene exhibited superior antifungal activity. Sc75 had an inhibitory effect of 69.25% ± 0.15% against M. oryzae and broad antifungal activity on other fungal plant pathogens in the dual culture assay. Its cell-free culture filtrate inhibited fungal growth and reduced mycelial mass. Also, the ethyl acetate crude extract completely inhibited conidia germination and appressoria formation on the hydrophobic coverslips and detached leaf at a concentration of 20 mg/ml. Its volatile organic compounds (VOCs) suppressed fungal growth by 98.42%. GC-MS analysis of the VOCs identified butanoic acid, 2-methyl-, methyl ester; di-tert-butyl peroxide; furan, 2-pentyl-; and undecanoic acid, 10-methyl-, methyl ester as the main components. In the greenhouse experiment, the disease severity was reduced and growth promotion was evident. Molecular investigation revealed that Sc75 upregulated defense-related genes involved in the synthesis of jasmonic acid, salicylic acid signaling pathway, and led to callose deposition and ROS production in the leaves. Finally, Sc75 produced hydrolytic enzymes, siderophore, indole acetic acid, gibberellic acid, phosphate solubilization, and 1-aminocyclopropane-1-carboxylate deaminase.

Conclusions: The rice rhizosphere soil harbors actinomycetes that can be explored as biocontrol agents against fungal pathogens such as M. oryzae. The isolate Sc75 had superior antifungal activity against M. oryzae and other selected plant pathogenic fungi. It showed remarkable antagonistic activity through direct antibiosis, production of VOCs, antifungal metabolites in the culture filtrates and crude extracts, and produced enzymes. In addition, the isolate promoted plant growth, reduced rice blast disease index in the greenhouse experiment, and elicited defense-related responses. Sc75 is a promising candidate for future exploration as a biofungicide and a biofertilizer.

Aims: Potato common scab (CS), caused by pathogenic Streptomyces, is a devastating disease affecting potato crops worldwide. Antagonistic microorganisms have been used as biological control agents to inhibit Streptomyces scabies and reduce the use of synthetic pesticides. However, identifying beneficial microorganisms for controlling CS remains undetermined.

Methods and results: Strain LS01 was isolated from the geocaulosphere soils of healthy potato tubers. In vitro and pot experiments demonstrated that strain LS01 significantly inhibited the mycelial growth and sporulation of S. scabies, thereby reducing the severity of CS. Sequencing of the 16S rRNA of LS01 indicated that the strain belonged to the species Bacillus safensis. Whole-genome sequencing, metabolomic analysis with liquid chromatograph mass spectrometer, and uultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry analyses indicated that hygromycin B and plantazolicin may be the active secondary metabolites by which B. safensis LS01 inhibits S. scabies.

Conclusions: Bacillus safensis LS01 is a potential biocontrol agent for CS, with its secondary metabolites exerting effective inhibitory effects.

Aims: Methicillin-resistant Staphylococcus aureus (MRSA) is an important zoonotic pathogen with multidrug-resistant phenotypes increasingly prevalent in both human and veterinary clinics. This study evaluated the potential of auranofin (AF) as an antibiotic adjuvant to enhance the anti-MRSA activity of florfenicol (FFC) and established a pharmacokinetic/pharmacodynamic (PK/PD) model to compare the efficacy of FFC alone or in combination with AF against MRSA.

Methods and results: We observed an increased susceptibility and significant synergistic effects of MRSA to FFC in the presence of AF. The combination treatment of FFC and AF significantly inhibited MRSA biofilm formation and decreased the metabolic activity of mature biofilms. Importantly, AF fully restored the efficacy of FFC in both Galleria mellonella larvae and murine models. PK/PD studies demonstrated that the AUC24h/MIC targets required to achieve the bacteriostatic and bactericidal effects were significantly lower with the combination therapy compared to florfenicol monotherapy.

Conclusions: These results reveal the potential of AF as a novel adjuvant to improve the efficacy of FFC in treating MRSA invasive infections and provide valuable PK/PD insights for designing effective combination therapies.

Aims: Biosurfactants are valuable eco-friendly compounds with broad industrial applications, particularly when produced sustainably using yeast and renewable carbon sources. Despite the potential of yeast in biosurfactant synthesis, little is known about the specific gene expression changes underlying this process. This study investigates the genetic response of Wickerhamomyces anomalus CCMA 0358 to biosurfactant production using waste cooking oil (WCO) as a low-cost carbon source.

Methods and results: During a 0-12 h fermentation period, RNA (ribonucleic acid) sequencing revealed 829 differentially expressed genes in W. anomalus grown with WCO, suggesting targeted metabolic adaptations. Pathway analysis showed WCO's significant impact on glycolysis, gluconeogenesis, and lipid biosynthesis. Gene ontology annotations further indicated adaptive responses in ribosome biogenesis and lipid metabolism, which are crucial for the efficient utilization of WCO. Notably, WCO induced the upregulation of very-long-chain fatty acid precursors and adjustments in glycolytic enzyme expression, both essential for biosurfactant production.

Conclusions: This study reveals, for the first time, the specific genetic pathways and metabolic adjustments that W. anomalus employs to produce biosurfactants from WCO. The increased expression of lipid metabolism enzymes and cell membrane components highlights a tailored adaptive mechanism for lipid-rich waste substrates, positioning W. anomalus as a promising candidate for sustainable biosurfactant production.

Aim: Ubiquitous magnesium transporter, CorA of Mycobacterium smegmatis is well known for its role in maintaining magnesium homeostasis. However, little is known about its involvement in exerting antimicrobial resistance. Here, by using molecular genetics, in vivo and in silico studies, we tried to envisage the role of CorA of M. smegmatis in antimicrobial resistance of M. smegmatis and Escherichia coli.

Methods and results: Expression of corA in M. smegmatis and E. coli decreased the susceptibility of the host cells towards various antibiotics and anti-tubercular drugs, which was elucidated by determining minimum inhibitory concentrations using the micro-broth dilution method. The intracellular antibiotic accumulation assay indicated that the host cells expressing corA accumulated less EtBr, norfloxacin, and ofloxacin than the control cells. Moreover, the presence of a sub-inhibitory concentration of Mg2+ further decreased the susceptibility towards the drugs tested. Furthermore, CorA enhanced the biofilm-forming ability of cells expressing it.

Conclusion: CorA (MSMEG_5056), a magnesium transporter of M. smegmatis influences the extrusion of multiple structurally unrelated classes of drugs and enhances the biofilm formation of E. coli and M. smegmatis.

Solid organ transplantation (SOT) recipients have a heightened risk for infection due to prolonged immunosuppressive drug use following transplant procedures. The occurrence of post-transplant infections is influenced not only by the transplanted organ type but also by varied factors. The kidney is the most common organ in SOT, followed by the liver, heart, and lung. This review aims to provide a comprehensive overview of the current epidemiological characteristics of infections after kidney, liver, heart, and lung transplantation, focusing on bacterial, fungal, and viral infections. The incidence and infection types demonstrated significant variability across different SOTs. Furthermore, this review attempts to elucidate the clinical characteristics of infections across patients following different SOTs and contribute to the development of individualized prevention strategies according to infection incidence, ultimately enhancing the quality of life of transplant recipients.