Adaptation of bacterial biotests for monitoring mycotoxins

Abstract

Mycotoxins are secondary fungal metabolites that have mutagenic, carcinogenic, teratogenic, immunomodulant and cytotoxic effects. Besides expensive chemical analytical methods, biotests can be alternative screening methods for selecting mycotoxin degrading microbes. Our aim was to monitor mycotoxins by bacterial biotests. Aflatoxin-B1 (AFB1), deoxynivalenol, zearalenon, T2-toxin and ochratoxin were analysed by two biotests: Aliivibrio fischeri luminescence assay and SOS-Chromotest using Escherichia coli. The A. fischeri bioluminescence assay is one of the most sensitive bacterial toxicity assays across a wide spectrum of toxicants; however, the effects of mycotoxins have been hardly examined. The inhibition effect of various mycotoxins on A. fischeri was determined in the range of 1-20 μg/ml toxin concentration. The test bacterium proved to be the most sensitive for AFB1. Less but pronounced inhibition of zearalenon was also determined, while other mycotoxins had no measurable toxic effect on A. fischeri. Based on these results we have adopted this method for monitoring microbial AFB1 biodegradation efficiency. The genotoxic effect of mycotoxins was analysed by SOS-Chromotest. The principle of the assay is the SOS response that is induced by DNA-damaging agents. We have examined AFB1 0,078-10 μg/ml concentration. We found that the genotoxic effect of AFB1 is still detectable at 0,078 μg/ml concentration. SOS-Chromotest was successfully used to select microorganisms that have the best AFB1 degrading potential and can degrade AFB1 without genotoxic by-products. The applicability of SOS-Chromotest for screening mycotoxin degrader microbes was confirmed by parallel ELISA and chemical analytical tests. We have adopted two bacterial biotests that are suitable for monitoring mycotoxin concentrations based on their biological effects. On the basis of these results a screening method was developed for microbes with AFB1 degrading potential. Furthermore, these methods can be appropriate tools for elucidating mycotoxin metabolism by high throughput screening of expression, and transposon mutagenesis clone libraries of the best AFB1 degrading strains.

Toxicological evaluation of feed contaminated with mycotoxins using a luminescent microorganism

“…The inhibitory effect of various mycotoxins (AFB1, DON, ZON, T2-toxin and ochratoxin) on the luminescence of another test culture of photobacteria (Aliivibrio fischeri) was detected at the concentration of toxins 1-20 μg/mL. The tested bacterium was most sensitive to AFB1, to a lesser extent (but with pronounced inhibition of luminescence) relative to ZON, while other mycotoxins did not affect the fluorescence intensity of A. fischeri (Krifaton et al, 2010). This is consistent with our data regarding AFB1 and ZON and contrary to the results obtained for DON, T2-toxin and ОТА, as they showed a pronounced inhibition of P. phosphoreum luminescence in the presence of their high content in feed.…”

The potency of bacterial field isolates for zearalenone and aflatoxin B1 detoxification in contaminated crop-origin raw material

“…Several authors recognize that the most promising method of detoxification of mycotoxins should be based on microbial biodegradation, because bacteria are able to suppress the production of mycotoxins in the mildest way without negative consequences for the environment and its objects [5,11]. The aflatoxin biodegradation by Mycobacterium fluoranthenivorans bacteria, Rhodococcus erythropolis has been reported [12,13,14]. There are studies that suggest that zearalenone can be degraded by Pseudomonas sp., Rhodococcus pyridinivorans and S. cerevisiae [15,16,17,18].…”

Aflatoxigenic Aspergillus flavus and Aspergillus parasiticus strains in Hungarian maize fields

“…The genotoxic effect of aflatoxin was detected from the supernatants with SOS chromotest TM kit (Environmental Bio-detection Products Inc., Ontario, Canada) according to the instructions of the manufacturer. Induction factor (IF) was calculated according to the report of Krifaton et al [29]. Samples with 1.5 or higher IF were considered genotoxic.…”