Unveiling the effect of interacting forecasted abiotic factors on growth and aflatoxin B1 production kinetics by Aspergillus flavus

Abstract

The aim was to decipher the temporal impact of key interacting climate change (CC) abiotic factors of temperature (30 vs 37 °C), water activity (aw; 0.985 vs 0.930) and CO2 exposure (400 vs 1000 ppm) on (a) growth of Aspergillus flavus and effects on (b) gene expression of a structural (aflD)and key regulatory gene (aflR) involved in aflatoxin B1 (AFB1) biosynthesis and (c) AFB1 production on a yeast extract sucrose medium over a period of 10 days. A. flavus grew and produced AFB1 very early with toxin detected after only 48 hours. Both growth and toxin production were significantly impacted by the interacting abiotic factors. The relative expression of the aflD gene was significantly influenced by temperature; aflR gene expression was mainly modulated by time. However, no clear relationship was observed for both genes with AFB1 production over the experimental time frame. The optimum temperature for AFB1 production was 30°C. Maximum AFB1 production occurred between days 4-8. Exposure to higher CO2 conditions simulating forecasted CC conditions, the amount of AFB1 produced in elevated temperature (37 °C) was higher than with the optimum temperature (30 °C) showing a potential for increased risk for human/animal health due to higher accumulation of AFB1.

Impacts of Climate Change Interacting Abiotic Factors on Growth, aflD and aflR Gene Expression and Aflatoxin B1 Production by Aspergillus flavus Strains In Vitro and on Pistachio Nuts

“…Most of the previous work on the resilience of A. flavus strains to climate changerelated abiotic factors has focused on those originating from maize [8,22]. On a conducive defined nutritional medium for toxin production, it was found that growth was unaffected by 650 or 800 ppm CO 2 exposure at 35 • C under freely available or water stress conditions.…”

“…This was supported by increased expression of biosynthetic genes involved in AFs production, including an early structural gene (aflD) and a regulatory gene (aflR) in biosynthetic pathway. Indeed, a subsequent kinetic study also showed that this stimulation of AFB 1 occurred when A. flavus was exposed on maize-based media to climate change scenarios [8].…”

“…The environmental chambers used included an inlet and outlet valve on either side and could be sealed during exposure and storage [8]. The in vitro and in situ treatments and replicates were placed into individual separate chambers.…”

“…The actual estimated atmospheric CO 2 concentration is, at present, approximately 417 ppm [12] and is predicted to double to 800 ppm (2×) or to 1000-1200 ppm (3×) in the future. This is suggestive of a temperature increase of 2-4 • C. Furthermore, rainfall patterns are also expected to change, with more extreme wet/dry episodes occurring [8,13]. Other important factors include the effect of light and also fluctuating day/night temperatures which can also impact colonization and toxin contamination of food commodities [14][15][16].…”

Resilience of Aspergillus westerdijkiae Strains to Interacting Climate-Related Abiotic Factors: Effects on Growth and Ochratoxin A Production on Coffee-Based Medium and in Stored Coffee

“…Medina et al [ 3 ] suggested that often while exposure of mycotoxigenic fungi such as A. flavus to interacting climate-related abiotic factors has little effect on growth, this does however result in a significant stimulation of aflatoxin B 1 (AFB 1 ) production on milled maize-based media and in stored maize. Indeed, recent studies have shown that the kinetics of AFB 1 production change over time when this species is exposed to climate-related abiotic factors [ 28 ]. This is supported by relative expression of key structural and regulatory genes involved in the biosynthesis of aflatoxins.…”