Abstract
Penicillium verrucosum, P. nordicum and Aspergillus carbonarius are three important ochratoxin A producing species. P. verrucosum is in addition able to produce citrinin. It has been shown earlier that P. nordicum is adapted to NaCl rich environments like salt rich dry cured foods or even salines. In this organism, the biosynthesis of ochratoxin A plays an adaptive role in this habitat. P. verrucosum generally can be found on cereals, but occasionally also on salt rich dry cured foods. In contrast A. carbonarius usually cannot be found in NaCl rich environments, but it occurs in another environment with high concentration of solutes, e.g., in sugar rich substrates like grapes and grape juices. Usually osmotic challenging conditions activate the HOG MAP kinase signal cascade, which in turn activates various osmo-regulated genes. In the current analysis, it could be demonstrated that in case of P. nordicum and P. verrucosum the NaCl induced production of ochratoxin A is correlated to the phosphorylation status of the HOG MAP kinase. Just the opposite was true for A. carbonarius. In this case, also higher amounts of NaCl in the medium lead to an increased phosphorylation status of HOG, but no increase in ochratoxin biosynthesis was observed. In contrast to the Penicillia, higher NaCl concentrations lead to a rapid cessation of growth by A. carbonarius. High glucose concentrations have much less impact on growth and the phosphorylation of HOG.
Highlights
Ochratoxin A is a nephrotoxic mycotoxin produced by some Aspergillus and Penicillium species.Because of the temperature and humidity preferences ochratoxigenic Aspergilli occur mainly in regions with elevated temperatures and occur on food commodities like coffee (A. westerdijkiae, A. steynii, A. ochraceus) [1], dried fruits (A. carbonarius, A. ochraceus) [2], spices (A. ochraceus) [3]or grapes (A. carbonarius) [4,5,6]
In order to analyze the influence of NaCl on growth and thereby on competitiveness of the three species under increasing NaCl conditions in the yeast extract sucrose medium (YES) medium, the diameters of the colony were measured after growth at 25 °C for five days (Aspergillus) or for nine days (Penicillium) because of the differential growth rates
NaCl concentrations, this species produced roughly no aerial mycelium and the colony looked very poor indicating the high stress conditions. Taken together these results suggest that the adaptation capacity to high NaCl conditions by the three ochratoxin A producing species reduces from P. nordicum to
Summary
Ochratoxin A is a nephrotoxic mycotoxin produced by some Aspergillus and Penicillium species.Because of the temperature and humidity preferences ochratoxigenic Aspergilli occur mainly in regions with elevated temperatures and occur on food commodities like coffee (A. westerdijkiae, A. steynii, A. ochraceus) [1], dried fruits (A. carbonarius, A. ochraceus) [2], spices (A. ochraceus) [3]or grapes (A. carbonarius) [4,5,6]. Ochratoxin A is a nephrotoxic mycotoxin produced by some Aspergillus and Penicillium species. Because of the temperature and humidity preferences ochratoxigenic Aspergilli occur mainly in regions with elevated temperatures and occur on food commodities like coffee (A. westerdijkiae, A. steynii, A. ochraceus) [1], dried fruits (A. carbonarius, A. ochraceus) [2], spices (A. ochraceus) [3]. Grapes (A. carbonarius) [4,5,6]. P. verrucosum can mainly be found on cereals and is responsible for the occurrence of ochratoxin A in cereal-based products [7]. P. nordicum often occurs in NaCl rich environments mainly in dry cured meats or cheeses but may even be found in pure NaCl [8,9,10]. Despite the fact that P. nordicum is the main ochratoxigenic species in
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