Mátyás Cserháti

A New Zearalenone Biodegradation Strategy Using Non-Pathogenic Rhodococcus pyridinivorans K408 Strain

Zearalenone (hereafter referred to as ZEA) is a nonsteroidal estrogenic mycotoxin produced by several Fusarium spp. on cereal grains. ZEA is one of the most hazardous natural endocrine disrupting chemicals (EDC) which induces hyper estrogenic responses in mammals. This can result in reproductive disorders in farm animals as well as in humans. Consequently, detoxification strategies for contaminated crops are crucial for food safety. In this study we have developed a bacterial based detoxification system using a non-pathogen Rhodococcus pyridinivorans K408 strain. Following 5 days treatment of ZEA with R. pyridinivorans K408 strain HPLC analyses showed an 87.21% ZEA-degradation efficiency of the bacterial enzyme systems. In another approach, the strain biotransformation ability has also been confirmed by a bioluminescent version of the yeast estrogen screening system (BLYES), which detected an 81.75% of biodegradability of ZEA, in a good agreement with the chemical analyses. Furthermore, the capacity of R. pyridinivorans to eliminate the estrogenic effects of ZEA was tested by using an immature uterotrophic assay. Prepubertal female rats were treated with vehicle (olive oil), 17β-estradiol, ZEA (0.1-1-5-10 mg/kg body weight) and LB broth containing 500 mg/l ZEA that has already been incubated with or without Rhodococcus pyridinivorans K408 strain. Uterine weights were measured and the mRNA level changes relating to apelin, aquaporin 5, complement component 2, and calbindin-3 genes were measured by qRT-PCR. These genes represent the major pathways that are affected by estromimetic compounds. Zearalenone feeding significantly increased the uterus weight in a dose dependent manner and at the same time upregulated complement component 2 and calbindin-3 expression as well as decreased apelin and aquaporin 5 mRNA levels comparable to that seen in 17β-estradiol exposed rats. In contrast, LB broth in which ZEA was incubated with Rhodococcus pyridinivorans K408 prior to the feeding did not display any estrogenic effect neither on uterine weight nor on the expression of estrogen-regulated genes. Consequently, the identification of Rhodococcus pyridinivorans K408 strain in ZEA biodegradation proved to be a very efficient biological tool that is able to eliminate the complete estrogenic effects of ZEA. It is also remarkable that this biotransformation pathway of ZEA did not result in any residual estrogenic effects.

Analysis of aflatoxin-B1-degrading microbes by use of a combined toxicity-profiling method

To monitor cytotoxic and genotoxic effects of aflatoxin, a luminescent assay employing Aliivibrio fischeri as a test organism and a colorimetric assay based on the SOS-Chromotest were adapted to our needs. The aim of this method-developing work was to be able to select - from a collection of environmental isolates - microbes that degrade aflatoxin without production of harmful intermediates and by-products, in a fast and cost-effective way. By the combination of the two modified assays, microbes that met these criteria have been successfully selected. Among thirty-three isolates, the strain Rhodococcus rhodochrous NI2 proved to be the best aflatoxin-B1-degrading microbe, with the weakest harmful biological effects throughout aflatoxin-B1-degradation. Our findings underline the necessity to employ bio-tests in biodegradation assays, as cytotoxicity and/or genotoxicity may occur even after substantial degradation of the toxins.

De Novo Genome Project of Cupriavidus basilensis OR16

Here we report on the complete genome sequence of Cupriavidus basilensis OR16 NCAIM BO2487. The genome of strain OR16 contains 7,534 putative coding sequences, including a large set of xenobiotics-degrading genes and a unique glucose dehydrogenase gene that is absent from other Cupriavidus genomes.

De Novo Genome Project for the Aromatic Degrader Rhodococcus pyridinivorans Strain AK37

Here, we present the complete genome sequence of Rhodococcus pyridinivorans AK37 strain NCAIM PB1376, which was isolated from an oil-polluted site in Hungary. R. pyridinivorans AK37 is an aerobic, nonsporulating, nonmotile, gram-positive bacterium with remarkable aromatic-decomposing activity.

Application of a yeast estrogen reporter system for screening zearalenone degrading microbes.

The aim of this study was to screen microbes for their zearalenone degrading potential and to select microbes whose activities do not create toxic or endocrine disrupting metabolites. Bioluminescent bioreporters (Saccharomyces cerevisiae BLYES and BLYR) were successfully used to monitor toxin degradation; the results of zearalenone biodegradation experiments were confirmed by parallel chemical analysis (HPLC-FLD) and immunoanalytical (ELISA) tests. Using the BLYES/BLYR bioreporters, the most appropriate microbes (ones that produced minimal toxic products and products with lower estrogenic potential) could be selected. The most promising strains belong to Streptomyces and Rhodococcus genera. Our findings demonstrate the benefit of using biological tests beside the analytical method, since bioreporters were able to monitor the samples for toxicity and estrogenic potential even after substantial degradation. We conclude that the BLYES/BLYR bioreporter system is a cost effective, fast and reliable tool for screening zearalenone-degrading microbes.

A New Ochratoxin A Biodegradation Strategy Using Cupriavidus basilensis Őr16 Strain

Ochratoxin-A (OTA) is a mycotoxin with possibly carcinogenic and nephrotoxic effects in humans and animals. OTA is often found as a contaminant in agricultural commodities. The aim of the present work was to evaluate OTA-degrading and detoxifying potential of Cupriavidus basilensis ŐR16 strain. In vivo administration of OTA in CD1 male mice (1 or 10 mg/kg body weight for 72 hours or 0.5 mg/kg body weight for 21 days) resulted in significant elevation of OTA levels in the blood, histopathological alterations- and transcriptional changes in OTA-dependent genes (annexinA2, clusterin, sulphotransferase and gadd45 and gadd153) in the renal cortex. These OTA-induced changes were not seen in animals that have been treated with culture supernatants in which OTA was incubated with Cupriavidus basilensis ŐR16 strain for 5 days. HPLC and ELISA methods identified ochratoxin α as the major metabolite of OTA in Cupriavidus basilensis ŐR16 cultures, which is not toxic in vivo. This study has demonstrated that Cupriavidus basilensis ŐR16 efficiently degrade OTA without producing toxic adventitious metabolites.

Taibaiella coffeisoli sp. nov., isolated from the soil of a coffee plantation.

A Gram-stain-negative, obligately aerobic, non-motile, non-sporulating, rod-shaped bacterium, designated TZCO2T, was isolated from the soil of an irrigated coffee plantation in Arusha, Tanzania, East Africa. Phylogenetic analysis, based on 16S rRNA gene sequences, indicated that the isolate is affiliated with the genus Taibaiella in the family Chitinophagaceae. Its closest relative is Taibaiella koreensis THG-DT86T (96.7%). The pH and temperature ranges for growth were pH 6.0-8.5 (optimum 7.0-7.5) and 10-35 °C (optimum 30 °C, respectively. The predominant fatty acids were iso-C15:0 (32.4%), iso-C15:1 G (22.6%), iso-C17:0 (15.1%) and iso-C17:0 3-OH (10.0%) The only isoprenoid quinone detected in strain TZCO2T was menaquinone-7 (MK-7); the major polar lipids were phosphoaminolipid, phosphatidylethanolamine, unidentified aminolipids and lipids. The DNA G+C content was 51.9 mol%. Physiological and chemotaxonomic data further confirmed that strain TZCO2T is distinct from other members of the genus Taibaiella. Thus, strain TZCO2T is considered to represent a novel species of the genus, for which the name Taibaiella coffeisoli sp. nov. is proposed. The type strain is TZCO2T (=NCAIM B 02601T=CCM 8601T).

Aflatoxigenic Aspergillus flavus and Aspergillus parasiticus strains in Hungarian maize fields

Due to the climate change, aflatoxigenic Aspergillus species and strains have appeared in several European countries, contaminating different agricultural commodities with aflatoxin. Our aim was to screen the presence of aflatoxigenic fungi in maize fields throughout the seven geographic regions of Hungary. Fungi belonging to Aspergillus section Flavi were isolated in the ratio of 26.9% and 42.3% from soil and maize samples in 2013, and these ratios decreased to 16.1% and 34.7% in 2014. Based on morphological characteristics and the sequence analysis of the partial calmodulin gene, all isolates proved to be Aspergillus flavus, except four strains, which were identified as Aspergillus parasiticus. About half of the A. flavus strains and all the A. parasiticus strains were able to synthesize aflatoxins. Aflatoxigenic Aspergillus strains were isolated from all the seven regions of Hungary. A. parasiticus strains were found in the soil of the regions Southern Great Plain and Southern Transdanubia and in a maize sample of the region Western Transdanubia. In spite of the fact that aflatoxins have rarely been detected in feeds and foods in Hungary, aflatoxigenic A. flavus and A. parasiticus strains are present in the maize culture throughout Hungary posing a potential threat to food safety.

EFFECT OF SHORT-TERM AFLATOXIN EXPOSURE IN COMBINATION WITH MEDICINAL HERB MIXTURE ON LIPID PEROXIDATION AND GLUTATHIONE REDOX SYSTEM IN LAYING HENS

Aflatoxins are well known hepatotoxic mycotoxins, which mainly contaminate the cereal grains. Those induce lipid peroxidation and impair the antioxidant, including glutathione redox system in long-term studies. The purpose of present study was to investigate the short-term (36-hour) effect of feeding aflatoxin B1 (AFB1) contaminated diet alone or in combination with a medicinal herb mixture on lipid peroxidation (conjugated dienes and trienes, and malondialdehyde), and on parameters of the glutathione system (reduced glutathione and glutathione peroxidase) in blood plasma, red blood cell haemolysate, liver and kidney homogenate of 49-week old Bovans Goldline laying hens. The results revealed that AFB1 (125 m /kg feed) did not have effect on feed intake, body and liver weight, but increased malondialdehyde content was observed in blood plasma and red blood cell haemolysate as effect of feeding AFB1 and medicinal herb mixture at 36th hour of the trial. However, the same diet resulted in lower malondialdehyde content in liver, but not in kidney. Reduced glutathione concentrations showed variance among treatments; thus due to inclusion of medicinal herb mixture in the diet lower values were measured in red blood cell haemolysate. Glutathione peroxidase activity was significantly lower in all treated groups as compared to the control at 36th hour of the trial in blood plasma, but not in other tissues. The results are contradictory with previous findings, probably due to the short-term exposure, and/or to medicinal herb mixture supplementation as it could moderately modify the effect of AFB1.