International Microbiology最新文献

Bacterial infections causing necrotic enteritis and diarrhea pose a considerable economic loss to the animal industry. Using mannose oligosaccharides as competitive exclusion agents is an alternative method to antibiotic growth promoters; however, these materials are rapidly metabolized by gut microbiota, posing a challenge in sustaining their efficacy. The aim of this study was to identify an agglutination material that is effective against pathogens. Polysaccharides and salts were assessed using agglutination assays, microscopy, and zeta potential analysis. Gum arabic (GA) demonstrated strong agglutination against Escherichia coli and Salmonella enterica. Potassium chloride altered the cell form of Clostridium perfringens from rod-like to coccoid. When combined with GA, KCl effectively agglutinated all three bacterial species tested. Zeta potential analysis showed that agglutination resulted from bacteria, GA, and KCl interactions. Among various salts mixed with GA, KCl was found to strongly agglutinate C. perfringens upon its change into the coccoid form. Moreover, this combination has been shown to agglutinate mixtures of pathogens, such as C. perfringens and S. enterica. Thus, a combination of GA and KCl offers a potential solution to combat the pathogens associated with necrotic enteritis and diarrhea in animals.

The major barrier to the wide-range application of biosurfactants is their high cost of production and low yield. In this study, waste frying oil (WFO) was used as the sole carbon source to produce cost-effective and eco-friendly rhamnolipids by Halopseudomonas sabulinigri OZK5 isolated from crude oil-contaminated soil samples. The optimal culture conditions for rhamnolipid production were determined as 30 ml/l waste frying oil, 37 °C temperature, pH 8, and 72 h incubation time. Under the optimized conditions 2.97 g/l rhamnolipid production was achieved. With a critical micelle concentration of 50 mg/l, the rhamnolipids could reduce the surface tension of water to 37.5 mN/m and demonstrate strong emulsifying activity (E24 = 67.3%). As a result of FTIR analyses, major peaks were obtained at 2924, 2854, 1720, 1570, 1396, 1051, and 981 cm^-1. In conclusion, rhamnolipid production by non-pathogenic Halopseudomonas sabulinigri OZK5 using a low-cost fermentation medium has been shown to be biotechnologically promising.

The present research work is concerned with the production and optimization of the dopa-oxidase enzyme by using pre-grown mycelia of Aspergillus oryzae. Different strains of A. oryzae were collected and isolated from various soil samples. Out of 32 isolated strains, isolates 19 and 27 were selected as they showed higher dopa-oxidase activity. Biomass harvesting was accomplished in a medium containing chloramphenicol as an antibiotic. The mycelia were filtered, washed with cold water, and stored at 4 ºC. A dopa-oxidase assay was performed, and absorbance was measured at a wavelength of 505 nm. Different physical parameters such as medium pH (6), temperature (30 ºC), and inoculum size (1.5% v/v) were optimized after the results of the assay. Other parameters like nitrogen requirements, biomass level (2 mg/ml), L-tyrosine (3.75 mg/ml), and L-ascorbic acid (8.75 mg/ml) concentrations were evaluated by reaction procedure. Certain micro and macronutrients and stabilizers, including Rochelle salt (20 µM), glycerol (25 µM), orthophosphoric acid (15 µM), and ethanol (20 µM), can also increase dopa-oxidase activity. In the last stage, the time of incubation (48 h) was optimized for maximum dopa-oxidase activity as well as L-dopaquinone production. Hence, from the results of the present study, it was observed that the activity of dopa-oxidase could be increased in the reaction mixture by the addition of various substances. They enhanced the dopa-oxidase activity up to 34.18 and 29.02 U/ml for isolates 19 and 27, respectively. In the future, dopa-oxidase can be used to produce stable L-dopaquinone from L-phenylalanine, which will provide clinical applications.

Ectoine, an osmolyte produced by various microorganisms, has numerous commercial applications. Vreelandella boliviensis (formerly called Halomonas boliviensis) generates high ectoine concentrations, i.e., 78.6 g/L. This study investigated three cultivation strategies for ectoine production in a non-aseptic air-lift bioreactor. The first strategy was performed in a repeated-batch mode with 5% (w/v) NaCl to induce cell growth, followed by the addition of solid NaCl to a final concentration of 12.5% (w/v) to prompt ectoine production. A maximum dry cell weight of 13.8 g/L at 46.5 h, a maximum ectoine concentration of 1.37 g/L at 37.5 h, and a maximum volumetric productivity of 0.93 g/L/d at 34.5 h were reached. The second strategy employed a three-step repeated-batch cultivation method. In the first step, cells were grown at the optimum salt concentration, harvested by centrifugation, and cultivated in a replenished medium for the second step. In the third step, the cells were harvested again and grown in a fresh medium containing 12.5% (w/v) NaCl. This strategy improved dry cell weight to 32 g/L, ectoine concentration to 4.37 g/L, and productivity to 1.76 g/L/day at 60 h of cultivation. The third strategy consisted of continuous cultivations that were investigated using different NaCl concentrations. The highest ectoine concentration of 2.83 g/L and productivity of 3.49 g/L/d were obtained with 8.5% (w/v) NaCl at a dilution rate of 0.05 (1/h). This study is the first to report ectoine production by V. boliviensis in continuous air-lift bioreactors under non-aseptic conditions.

This study re-evaluates Pseudofrankia strains, traditionally regarded as parasitic dwellers of actinorhizal root nodules due to their inability to fix nitrogen (Fix -) and/or nodulate (Nod -), as potential plant growth-promoting bacteria (PGPB). We compared plant growth-promoting traits (PGPTs) between Pseudofrankia strains, including one newly sequenced strain BMG5.37 in this study and typical (Fix + /Nod +) Frankia, Protofrankia, and Parafrankia, as well as non-frankia actinorhizal species Nocardia and Micromonospora, and the phytopathogenic Streptomyces. Although lacking nitrogen-fixing genes typically found in mutualistic Frankiaceae strains, Pseudofrankia may compensate through predicted pathways for denitrification and nitrate utilization. Functional profiling suggests potential for phosphorus solubilization, gibberellin production, and vitamin metabolism, as well as bioremediation of pollutants. Pseudofrankia strains are predicted to show moderate resistance to heavy metals, with a stronger tolerance to arsenic and tellurium compared to Frankia. Furthermore, they are anticipated to exhibit significant biotic and abiotic stress resistance, including oxidative and osmotic stress. Predictive data also indicate that Pseudofrankia strains may have root colonization abilities and may play a role in plant signaling and phytohormone production, particularly in auxin and gibberellin pathways. Secretion systems, especially CE-Type VI, are predicted to be highly developed in Pseudofrankia, suggesting potential for effective plant interactions. These findings position Pseudofrankia strains as promising candidates for plant growth promotion, although experimental validation and the integration of transcriptomic or proteomic data are needed to confirm these predictions.

Antibiotic therapy has been the most popular line of treatment for the control of mastitis worldwide during the last few decades. Alternative and sustainable treatments must be developed because pathogens are becoming more resistant to antibiotics, leading to the development and spread of antimicrobial resistance (AMR). The aim of the current investigation was to isolate lactic acid bacteria (LAB) with probiotic potential that can inhibit mastitis-causing pathogens to prevent bovine mastitis. Milk samples were collected from Sahiwal cows, and a total of 150 bacteria were isolated, of which 76 were found to be catalase negative, and resistant to vancomycin. Twenty-three isolates displayed greater acid and bile tolerance, with > 90% survivability, and were molecularly characterized by 16S rRNA partial sequencing. The autoaggregation percentages for SML7 and SML41 were greater (p<0·05) 80.38±0.19% and 80.28±0.04%, respectively. SML10 (92.04±0.26 μmol/mL) had the highest (p<0.05) ferric-reducing antioxidant power (FRAP) activity, while SML20 (52.1±0.99%) had the highest 1,1 diphenyl 2 picrylhydrazyl (DPPH) scavenging activity. All the strains were nonhemolytic or nonmucinolytic. The highest antimicrobial activity was observed in several strains (SML41, SML63, SML76, and SML60) against common mastitis-causing pathogens, namely, E. coli ATCC25922, Staphylococcus aureus ATCC25923, Enterococcus faecalis NCDC114, Streptococcus agalactiae NCDC208, and Enterococcus faecium NCDC124. The coaggregation efficacy of SML20 with S. aureus was the highest (67.69±1.21%), while SML41 showed the highest (69.75±0.29%) coaggregation efficacy with E. faecalis NCDC114 and SML63 (68.078±0.26) with S. agalactiae NCDC208. Overall, seven distinct lactic acid bacterial clusters were identified by cluster analysis of the phylogenetic tree as follows: Enterococcus hirae (1), Limosilactobacillus reuteri (1), Pediococcus acidilactici (4), Weissella confusa (11), Lactobacillus helveticus (3), Limosilactobacillus balticus (2), and Lacticaseibacillus rhamnosus (1). The Lactobacillus helveticus SML41, Lactobacillus helveticus SML60, Weissella confusa SML61, Lacticaseibacillus rhamnosus SML63, Weissella confusa SML64, and Pediococcus acidilactici SML76 isolates were found to possess the most desirable characteristics of potential probiotics based on principal component analysis (PCA). Therefore, the strains chosen in the current investigation demonstrated techno-functional characteristics that rendered them appropriate for probiotic use to treat and prevent intramammary infections in dairy cattle in a sustainable manner.

The spectrum of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) ranges from minor conditions to potentially life-threatening diseases. The rising antibiotic resistance in MRSA often leads to treatment failures, underscoring the urgent need for novel eradication strategies. This study focuses on isolating MRSA from burn patients, determining its antibiogram profile, and isolating and characterizing bacteriophages from sewage water that target MRSA, alongside conducting genomic analysis of the phages. A total of 70 samples were collected from burn patients, with MRSA identification and characterization performed using a combination of biochemical and molecular techniques, as well as antibiotic sensitivity testing. Based on host range analysis, a specific phage (phage-3) was selected for detailed characterization, including proteomic analysis, genetic mapping, phylogenetic studies, and analysis of open reading frames (ORFs) and motifs. The prevalence of MRSA in the samples was found to be 28.6%. Antibiotic susceptibility tests indicated that 94% of the MRSA isolates were sensitive to tobramycin and gentamicin, while vancomycin exhibited the lowest sensitivity, with only 2% effectiveness. Using the soft agar overlay method, three bacteriophages (phage-1, phage-2, and phage-3) were successfully isolated from sewage water. Among these, phage-3 exhibited the broadest host range. Further analysis showed that phage-3 demonstrated optimal activity at pH levels between 6 and 8, and within a temperature range of 20-40 °C. Phage-3 also displayed a rapid adsorption phase within the first 0-5 min, and its one-step growth curve revealed a latent period lasting up to 30 min, followed by a significant increase in titer from 30 to 50 min. Proteomic analysis of phage-3 identified the presence of 33 kDa and 65 kDa proteins. Phylogenetic analysis showed that phage-3 shares 96.6% similarity with Mammallicoccus phage vB_MscM-PMS3. The ORF analysis identified 80 potential ORFs within the phage's entire genome.

During the course of two independent studies, six conspecific yeast strains were recovered from flowers, soil, bird faeces and wood of different geographical origins. The six strains share identical DNA sequences in two barcoding regions, the D1/D2 domain of the LSU rRNA gene and the internal transcribed spacer (ITS) region (ITS1-5.8S rRNA gene-ITS2). According to sequence comparisons and phylogenetic analysis, they represent an undescribed Wickerhamia species. The novel species is not only genetically distinct from W. fluorescens, the single species of the genus but can also be distinguished from it by some phenotypic characters. We propose Wickerhamia europaea sp. nov. (holotype: NCAIM Y.01938; isotype: CBS 18675; MycoBank no.: 856571) to accommodate the above noted strains. Under certain fermentation conditions, we detected the production of phenyllactic acid, a potential broad-spectrum antimicrobial compound against food-borne pathogens, by the type strain of the novel species, although in smaller concentrations than in the case of W. fluorescens. Comparing our observations on the formation and properties of the ascospores of Wickerhamia europaea sp. nov. and the ambiguous data on the number of ascospores per ascus of W. fluorescens, we suggest a possible explanation to reconcile the different data regarding the number of ascospores per ascus formed by W. fluorescens.

Probiotics have been shown to improve host access to vitamins, generate vitamins and improve gastrointestinal tract functions throughout transit yeasts which are indicated to potentially function as probiotics with some health benefits. The aim of this study was to evaluate the probiotic potential of yeast isolates from banana and plantain peels. Yeast strains were isolated from ripe banana and plantain peels, using the standard procedures. Isolates that showed negativity for pathogenicity assays were used for in vitro and in vivo probiotic screening. For the in vivo assay, 30 male Wistar rats, divided into six treatment groups (five rats per treatment), were used. At the expiration of administration, the rats were euthanized for the estimation of yeast translocation and haematological parameters. A total of 16 yeasts were isolated, out of which, five (Hanseniaspora uvarum, Hanseniaspora lachancei, Hanseniaspora opuntiae and two species of Kodamaea ohmeri) isolates that showed negative results for pathogenicity assays were used for in vitro and in vivo assays. The study revealed the growth of the test yeast strains at the different incubation temperatures (25-45 °C) and pH (4-9). However, significantly highest growths were observed at pH 4 and 5 and NaCl concentration of 4%. All the isolates showed remarkable growth at the bile concentrations used. In addition, the strains showed resistance to the antibiotics and antimycotics at the concentration used for investigation. In vivo assay results showed no significant differences between weight gain, haematological parameters and behavioural scores between control and treatment groups of the rats. The ability of the yeasts to show tolerance to stress conditions and lack of negative impacts to haematological, behavioural and yeast translocations are indications of their probiotic capabilities.

Rhinoviruses (RVs), particularly RV-C, frequently cause acute respiratory infections and asthma exacerbations. However, there is a lack of routine detection methods. Thus, this study aims to develop a rapid molecular and differential diagnostic detection method for RV-C using the reverse transcription (RT) loop-mediated isothermal amplification (LAMP) approach. The RT-LAMP assay targeting the 5'UTR region of RV-C genome was optimized by varying the reaction temperature, magnesium sulphate, betaine concentrations, and reaction time. Compared with conventional RT-PCR with a sensitivity of 10⁶ copies of RNA, RT-LAMP demonstrated a significant increase in efficiency and sensitivity with a quantifiable viral load of at least 10¹ copies of RNA by gel electrophoresis and colour change, and 10⁴ copies of RNA for end-point detection with a turbidimeter for 40 min. The assay is also specific without amplifying RV-A16 and RV-B72 genomic RNA. In the proof-of-concept assay using 30 clinical respiratory samples with known etiological agents, it detected all RV-C isolates, of which its accuracy was confirmed by sequencing. The newly developed RT-LAMP assay demonstrated good analytical sensitivity and specificity toward RV-C. The assay provides an alternative for improved RV-C diagnosis.