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Applied and Environmental Microbiology Nov 2021Mitigation strategies to prevent microbial contamination of crops are lacking. We tested the hypothesis that induction of plant systemic resistance by biological...
Mitigation strategies to prevent microbial contamination of crops are lacking. We tested the hypothesis that induction of plant systemic resistance by biological (induced systemic resistance [ISR]) and chemical (systemic acquired resistance [SAR]) elicitors reduces endophytic colonization of leaves by Salmonella enterica serovars Senftenberg and Typhimurium. . Senftenberg had greater endophytic fitness than Typhimurium in basil and lettuce. The apoplastic population sizes of serovars Senftenberg and Typhimurium in basil and lettuce, respectively, were significantly reduced approximately 10- to 100-fold by root treatment with microbial inducers of systemic resistance compared to HO treatment. effected the lowest population increases of Typhimurium in lettuce and . Senftenberg in basil leaves, respectively 120- and 60-fold lower than those seen with the HO treatment over 10 days postinoculation. and did not have any significant effect on . Senftenberg in the basil apoplast. The chemical elicitors acidobenzolar--methyl and dl-β-amino-butyric acid inhibited Typhimurium multiplication in the lettuce apoplast 10- and 2-fold, respectively, compared to HO-treated plants. All ISR and SAR inducers applied to lettuce roots in this study increased leaf expression of the defense gene , as did Salmonella apoplastic colonization in HO-treated lettuce plants. Remarkably, both acidobenzolar--methyl upregulation and upregulation of were repressed by the presence of Salmonella in the leaves. However, enhanced expression was sustained longer and at greater levels upon elicitor treatment than by Salmonella induction alone. These results serve as a proof of concept that priming of plant immunity may provide an intrinsic hurdle against the endophytic establishment of enteric pathogens in leafy vegetables. Fruit and vegetables consumed raw have become an important vehicle of foodborne illness despite a continuous effort to improve their microbial safety. Salmonella enterica has caused numerous recalls and outbreaks of infection associated with contaminated leafy vegetables. Evidence is increasing that enteric pathogens can reach the leaf apoplast, where they confront plant innate immunity. Plants may be triggered for induction of their defense signaling pathways by exposure to chemical or microbial elicitors. This priming for recognition of microbes by plant defense pathways has been used to inhibit plant pathogens and limit disease. Given that current mitigation strategies are insufficient in preventing microbial contamination of produce and associated outbreaks, we investigated the effect of plant-induced resistance on S. enterica colonization of the lettuce and basil leaf apoplast in order to gain a proof of concept for the use of such an intrinsic approach to inhibit human pathogens in leafy vegetables.
Topics: Disease Resistance; Lactuca; Ocimum basilicum; Plant Immunity; Plant Leaves; Plant Proteins; Salmonella enterica; Salmonella typhimurium
PubMed: 34613760
DOI: 10.1128/AEM.01151-21 -
Journal of Fungi (Basel, Switzerland) Sep 2021Wheat grains are colonized by complex microbial communities that have the potential to affect seed quality and susceptibility to disease. Some of the beneficial microbes...
Wheat grains are colonized by complex microbial communities that have the potential to affect seed quality and susceptibility to disease. Some of the beneficial microbes in these communities have been shown to protect plants against pathogens through antagonism. We evaluated the role of the microbiome in seed health: in particular, against mycotoxin-producing fungi. Amplicon sequencing was used to characterize the seed microbiome and determine if epiphytes and endophytes differ in their fungal and bacterial diversity and community composition. We then isolated culturable fungal and bacterial species and evaluated their antagonistic activity against mycotoxigenic fungi. The most prevalent taxa were found to be shared between the epiphytic and endophytic microbiota of stored wheat seeds. Among the isolated bacteria, strains exhibited strong antagonistic properties against fungal pathogens with noteworthy fungal load reduction in wheat grain samples of up to a 3.59 log CFU/g compared to untreated controls. We also found that a strain of the yeast, , isolated from wheat grains, degrades and/or metabolizes aflatoxin B, one of the most dangerous mycotoxins that negatively affects physiological processes in animals and humans. The mycotoxin level in grain samples was significantly reduced up to 65% in the presence of the yeast strain, compared to the untreated control. Our study demonstrates that stored wheat grains are a rich source of bacterial and yeast antagonists with strong inhibitory and biodegradation potential against mycotoxigenic fungi and the mycotoxins they produce, respectively. Utilization of these antagonistic microorganisms may help reduce fungal and mycotoxin contamination, and potentially replace traditionally used synthetic chemicals.
PubMed: 34575819
DOI: 10.3390/jof7090781 -
Foods (Basel, Switzerland) Aug 2021In the last decades, several plant-based materials were used for the substitution of fish meal and oil in aquaculture. The present study evaluated the fish quality and...
In the last decades, several plant-based materials were used for the substitution of fish meal and oil in aquaculture. The present study evaluated the fish quality and the sensory differences of rainbow trout () and pike-perch () from three different feeding groups, which were fed a commercially available industrial (standard) diet, a control diet, and a special microorganism-based feed mix. This feed mainly consisted of a mix made of and sp. and had 50% less fish meal and fish oil compared to typical control diets. At the beginning, the pike-perch population was six months old, and the rainbow trout population was 15 months old. The feeding study duration was 16 weeks and every four weeks the growth performance and several morphometric parameters were recorded. Afterwards, sensory evaluation took place to identify possible trends. Sensory evaluation revealed that the rainbow trout groups did not show any significant differences to the standard and control fish fillets with regard to odor, texture, and taste. The effects on rainbow trout growth performances and carcass parameters were similar to the standard group. The feed mix was not optimal for pike-perch farming, which was also reflected by significantly adversely affected growth performance and carcass parameters. The sensorial evaluation showed an opposite trend: here, only small differences in the fillets from the feed mix and standard/control diet were observed.
PubMed: 34441576
DOI: 10.3390/foods10081799 -
Biotechnology For Biofuels May 2021Microbial oils, generated from lignocellulosic material, have great potential as renewable and sustainable alternatives to fossil-based fuels and chemicals. By...
BACKGROUND
Microbial oils, generated from lignocellulosic material, have great potential as renewable and sustainable alternatives to fossil-based fuels and chemicals. By unravelling the diversity of lipid accumulation physiology in different oleaginous yeasts grown on the various carbon sources present in lignocellulose hydrolysate (LH), new targets for optimisation of lipid accumulation can be identified. Monitoring lipid formation over time is essential for understanding lipid accumulation physiology. This study investigated lipid accumulation in a variety of oleaginous ascomycetous and basidiomycetous strains grown in glucose and xylose and followed lipid formation kinetics of selected strains in wheat straw hydrolysate (WSH).
RESULTS
Twenty-nine oleaginous yeast strains were tested for their ability to utilise glucose and xylose, the main sugars present in WSH. Evaluation of sugar consumption and lipid accumulation revealed marked differences in xylose utilisation capacity between the yeast strains, even between those belonging to the same species. Five different promising strains, belonging to the species Lipomyces starkeyi, Rhodotorula glutinis, Rhodotorula babjevae and Rhodotorula toruloides, were grown on undiluted wheat straw hydrolysate and lipid accumulation was followed over time, using Fourier transform-infrared (FTIR) spectroscopy. All five strains were able to grow on undiluted WSH and to accumulate lipids, but to different extents and with different productivities. R. babjevae DVBPG 8058 was the best-performing strain, accumulating 64.8% of cell dry weight (CDW) as lipids. It reached a culture density of 28 g/L CDW in batch cultivation, resulting in a lipid content of 18.1 g/L and yield of 0.24 g lipids per g carbon source. This strain formed lipids from the major carbon sources in hydrolysate, glucose, acetate and xylose. R. glutinis CBS 2367 also consumed these carbon sources, but when assimilating xylose it consumed intracellular lipids simultaneously. Rhodotorula strains contained a higher proportion of polyunsaturated fatty acids than the two tested Lipomyces starkeyi strains.
CONCLUSIONS
There is considerable metabolic diversity among oleaginous yeasts, even between closely related species and strains, especially when converting xylose to biomass and lipids. Monitoring the kinetics of lipid accumulation and identifying the molecular basis of this diversity are keys to selecting suitable strains for high lipid production from lignocellulose.
PubMed: 34051838
DOI: 10.1186/s13068-021-01974-2 -
Journal of Fungi (Basel, Switzerland) Mar 2021was analyzed for the production of secondary metabolites, resulting in the isolation of known zopfinol () and its new derivatives zopfinol B-C (), the 10-membered...
was analyzed for the production of secondary metabolites, resulting in the isolation of known zopfinol () and its new derivatives zopfinol B-C (), the 10-membered lactones 7-O-acetylmultiplolide A () and 8-O-acetylmultiplolide A (), together with sordarin (), sordarin B (), and hypoxysordarin (). The absolute configuration of was elucidated by the synthesis of MPTA-esters. Compound showed antimicrobial activity against the Gram-positive bacteria and and the fungus . While was weakly antibacterial, showed stronger antibiotic activity against the Gram-positive bacteria and weak antifungal activity against and . We furthermore observed the cytotoxicity of , and against the mammalian cell lines KB3.1 and L929. Moreover, the new genus is introduced herein to accommodate together with several species of -, , and . These taxa formed a well-supported monophyletic clade in the recently introduced family Navicularisporaceae, located far from the type species of the respective original genera, in a phylogram based on the combined dataset sequences of the internal transcribed spacer region (ITS), the nuclear rDNA large subunit (LSU), and fragments of the ribosomal polymerase II subunit 2 () and β-tubulin () genes. is synonymized with due to the phylogenetic and morphological similarity. The isolation of zopfinols - and sordarins - confirms the potential of this fungal order as producers of bioactive compounds and suggests these compounds as potential chemotaxonomic markers.
PubMed: 33802411
DOI: 10.3390/jof7030181 -
Frontiers in Cellular and Infection... 2021The occurrence of multidrug-resistant isolates and the increased mortality associated with invasive infections or outbreaks due to this species have been reported in...
The occurrence of multidrug-resistant isolates and the increased mortality associated with invasive infections or outbreaks due to this species have been reported in many healthcare settings. Therefore, accurate and rapid identification at the species level of clinical isolates as well as their timely differentiation as susceptible or resistant to antifungal drugs is mandatory. Aims of the present study were to implement the MALDI-TOF mass spectrometry (MS) Bruker Daltonics Biotyper database with spectrum profiles and to develop a fast and reproducible MS assay for detecting anidulafungin (AFG) resistance in isolates. After creation of main spectra, a score-oriented dendrogram was generated from hierarchical cluster analysis, including spectra of isolates from and other (, , , , and ) or non- () species. Cluster analysis allowed to group and classify the isolates according to their species designation. Then, a three-hour incubation antifungal susceptibility testing (AFST) assay was developed. Spectra obtained at null, intermediate, or maximum AFG concentrations were used to create composite correlation index matrices for eighteen isolates included in the study. All six resistant isolates were detected as resistant whereas 11 of 12 susceptible isolates were detected as susceptible by the MS-AFST assay. In conclusion, our MS-based assay offers the possibility of rapidly diagnosing and appropriately treating patients with infection.
Topics: Antifungal Agents; Candidiasis, Invasive; Cross Infection; Humans; Microbial Sensitivity Tests; Rhodotorula; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
PubMed: 33796487
DOI: 10.3389/fcimb.2021.645049 -
Biotechnology For Biofuels Mar 2021Crude glycerol (CG) and hemicellulose hydrolysate (HH) are low-value side-products of biodiesel transesterification and pulp-and paper industry or lignocellulosic...
BACKGROUND
Crude glycerol (CG) and hemicellulose hydrolysate (HH) are low-value side-products of biodiesel transesterification and pulp-and paper industry or lignocellulosic ethanol production, respectively, which can be converted to microbial lipids by oleaginous yeasts. This study aimed to test the ability of oleaginous yeasts to utilise CG and HH and mixtures of them as carbon source.
RESULTS
Eleven out of 27 tested strains of oleaginous yeast species were able to grow in plate tests on CG as sole carbon source. Among them, only one ascomycetous strain, belonging to Lipomyces starkeyi, was identified, the other 10 strains were Rhodotorula spec. When yeasts were cultivated in mixed CG/ HH medium, we observed an activation of glycerol conversion in the Rhodotorula strains, but not in L. starkeyi. Two strains-Rhodotorula toruloides CBS 14 and Rhodotorula glutinis CBS 3044 were further tested in controlled fermentations in bioreactors in different mixtures of CG and HH. The highest measured average biomass and lipid concentration were achieved with R. toruloides in 10% HH medium mixed with 55 g/L CG-19.4 g/L and 10.6 g/L, respectively, with a lipid yield of 0.25 g lipids per consumed g of carbon source. Fatty acid composition was similar to other R. toruloides strains and comparable to that of vegetable oils.
CONCLUSIONS
There were big strain differences in the ability to convert CG to lipids, as only few of the tested strains were able to grow. Lipid production rates and yields showed that mixing GC and HH have a stimulating effect on lipid accumulation in R. toruloides and R. glutinis resulting in shortened fermentation time to reach maximum lipid concentration, which provides a new perspective on converting these low-value compounds to microbial lipids.
PubMed: 33712047
DOI: 10.1186/s13068-021-01916-y -
Frontiers in Bioengineering and... 2020PAL (phenylalanine ammonia lyase) is important for secondary metabolite production in plants and microorganisms. There is broad interest in engineering PAL for its...
PAL (phenylalanine ammonia lyase) is important for secondary metabolite production in plants and microorganisms. There is broad interest in engineering PAL for its biocatalytic applications in industry, agriculture, and medicine. The production of quantities of high-activity enzymes has been explored by gene cloning and heterogeneous expression of the corresponding protein. Here, we cloned the cDNA of PAL (PAL) and introduced codon optimization to improve protein expression in and enzyme activities . The PAL gene was cloned by reverse transcription and named -wt. It had a full-length of 2,121 bp and encoded a 706-amino-acid protein. The -wt was inefficiently expressed in , even when the expression host and physical conditions were optimized. Therefore, codon optimization was used to obtain the corresponding gene sequence, named -opt, in order to encode the same amino acid for the PAL protein. The recombinant protein encoded by -opt, named PAL-opt, was successfully expressed in and then purified to detect its enzymatic activity . Consequently, 55.33 ± 0.88 mg/L of PAL-opt protein with a specific activity of 1,219 ± 147 U/mg and value of 609 μM for substrate L-phenylalanine was easily obtained. The enzyme protein also displayed tyrosine ammonia lyase (TAL)-specific activity of 80 ± 2 U/mg and value of 13.3 μM for substrate L-tyrosine. The bifunctional enzyme PAL/TAL (PAL-opt) and its easy expression advantage will provide an important basis for further applications.
PubMed: 33614604
DOI: 10.3389/fbioe.2020.610506 -
Mikrobiyoloji Bulteni Jan 2021Rhodotorula species are yeasts that are common in the environment,but are not frequently encountered as an infectious agent in humans. Rhodotorula mucilaginosa,...
Rhodotorula species are yeasts that are common in the environment,but are not frequently encountered as an infectious agent in humans. Rhodotorula mucilaginosa, Rhodotorula glutinis and Rhodotorula minuta are the species that cause disease in humans. Although its isolation from mucosa is doubtful in terms of the presence of true infection, it is more frequently encountered in daily practice due to the increasing number of invasive procedures, immune system deficiencies caused by immunosuppressive drugs and diseases. R.mucilaginosa growth isolated from various clinical samples between 2000 and 2018 in a tertiary university hospital was presented in this case report. The first case was an 82-year-old man with chronic lung disease, hypertension, congestive heart failure and acute leukemia causing severe immunosuppression. Use of broad spectrum antibiotics, history of immunosuppressive therapy, presence of jugular catheter were the risk factors in this patient. R.mucilaginosa was isolated from blood culture while the patient was receiving fluconazole treatment for Candida albicans grown in urine culture and the patient died before starting the treatment. The second case was a 34-year-old female patient with congenital heart disease. Discharge was observed at the intracardiac defibrillator site of the patient, a temporary pacemaker was inserted, and she used broad spectrum antibiotics for a long time. When the yeast growth was reported in the blood culture, caspofungin treatment was initiated. Although the treatment was switched to amphotericin B lipid complex after the culture result was reported as R.mucilaginosa, the patient died after 12 hours. The third case was a 70-year-old woman with hypertension, dementia, diabetes mellitus and rheumatoid arthritis admitted to the intensive care unit due to cerebrovascular accident. She received different immunosuppressive treatments and had invasive procedures. R.mucilaginosa was isolated from the blood culture taken from the patient's catheter, and there was no growth in the blood culture obtained from the peripheral vein. Anidulafungin was started empirically, which was changed to amphotericin B lipid complex after the identification of the yeast. The patient died for various reasons 10 days after the antifungal treatment was stopped. Our last case was a 55-year-old woman with metastatic ovarian cancer and secondary ascites. Broad-spectrum multiple antibiotics were used and invasive procedures were performed. R.mucilaginosa and C.albicans were isolated from the urine of the patient who had a urinary catheter. No growth was detected from urine after changing the urinary catheter. Therefore, growths were evaluated as colonization, and fluconazole was administered for C.albicans due to the high risk of invasive infection. The patient was lost for different reasons. The development and diversity of the treatment methods lead to the emergence of some opportunistic infectious agents that were not observed previously. Rhodotorula species are one of the rare agents that have increased over the years. Rhodotorula species should be considered as the cause of an infection if no clinical response is obtained after echinocandin and/or fluconazole treatment in patients with long-term immunosuppression and invasive procedures. Data on clinical pictures, treatment responses, follow-up and treatment results of this rare yeast are still limited. This case series was presented to draw attention to the risk factors related to R.mucilaginosa infection/colonization, clinical characteristics of the patients, follow-up results and treatment options and to contribute to the literature.
Topics: Adult; Aged; Aged, 80 and over; Antifungal Agents; Fatal Outcome; Female; Fungemia; Humans; Male; Middle Aged; Mycoses; Rhodotorula; Tertiary Care Centers; Turkey
PubMed: 33590984
DOI: 10.5578/mb.20188 -
Biotechnology For Biofuels Dec 2020Converting wastewater sludge to lipid is considered as one of the best strategies of sludge management. The current problem of lipid production from wastewater sludge is...
BACKGROUND
Converting wastewater sludge to lipid is considered as one of the best strategies of sludge management. The current problem of lipid production from wastewater sludge is the low yield (0.10-0.16 g lipid/g dry sludge) due to the low availability of easily uptaken materials (such as soluble monosaccharide and oligosaccharide) in sludge to oleaginous microorganism (Rhodotorula glutinis, Trichosporon oleaginosus, Lipomyces starkeyi). Pretreatments are efficient methods to improve sludge bioavailability. This study is aimed to achieve high lipid production from sludge and high sludge reduction.
RESULTS
In this study, it was observed that the soluble chemical oxygen demand (SCOD) had significantly increased after different pretreatment. The SCOD in the supernatant was increased from 32.64 to 180.25 mg/L, 924.16 mg/L, 1029.89 mg/L and 3708.31 mg/L after acidic (pH 2 for 2 h), alkaline (pH 12 for 2 h), microwave irradiation (15 min with 5 min interval), and ultrasonication (30 min at 450 W and 20 kHz frequency with 5 s on and 2 s off mode) pretreatment, respectively. Pretreatments have also increased the release of total nitrogen (TN) and total phosphorus (TP) from solids. The sludge after different pretreatments were used as a medium for lipid production, and the highest lipid content (36.67% g/g) was obtained in the fermentation with ultrasonication pretreatment sludge, and the sludge reduction was 63.10%. For other pretreatments, the lipid content and sludge reduction were 18.42% and 32.63% in acid pretreatment case, 21.08% and 36.44% in alkaline pretreatment case, and 26.31% and 43.03% in microwave pretreatment case, respectively.
CONCLUSION
It was found that ultrasonication pretreatment was the most efficient way to increase the sludge biodegradability (SCOD) and to release TN and TP from solid phase to liquid phase. Pretreated sludge for lipid production achieved significant improvement in lipid yield and sludge reduction. Lipids produced from pretreated sludge were transesterified to biodiesel and the analysis showed that biodiesel had a similar composition as commercial biodiesel. The study reveals that pretreatment on sludge is a promising method for enhancing biological sludge management efficiency.
PubMed: 33317613
DOI: 10.1186/s13068-020-01844-3