Aflatoxin genes and the aflatoxigenic potential of Koji moulds.
Sixty-four Aspergillus isolates, 54 of which originated from food fermentations, and 18 Aspergillus reference strains were identified and screened for the presence of aflatoxin genes aflR and omt-1. Among the Koji moulds, not only A. oryzae but also A. flavus strains were found. Furthermore, 27% of A. oryzae and 93% of A. flavus strains lacked either aflR or both aflR- and omt-1. A selection of 29 strains was also checked for the presence of pksA and nor-1. This revealed large deletions in the aflatoxin gene cluster of some strains. The hybridisation patterns also suggested a polarity in the deletion events, originating in the vicinity of pksA and extending towards omt-1. Other strains exhibited BamHI restriction fragment length polymorphisms (RFLPs) for either aflR or for aflR and omt-1. All aflR and/or omt-1 deletion strains turned out to be unable to produce aflatoxin. The RFLP-carrying strains either produced only traces of aflatoxin or none at all. In 73% of the A. oryzae strains, no apparent deletions were detected with the aflR and omt-1 probes. Nevertheless, after incubation in aflatoxin-inducing media, no aflatoxin B1 production could be detected in those A. oryzae strains.
van den Broek
P
P
Nestlé Research Centre, Lausanne, Switzerland. peter.van-den-broek@rdls.nestle.com
Pittet
A
A
Hajjaj
H
H
D000348:Aflatoxins / Q000096:biosynthesis / Q000235:genetics*; D001230:Aspergillus / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015139:Blotting, Southern; D017931:DNA Primers; D017353:Gene Deletion; D005810:Multigene Family; D012150:Polymorphism, Restriction Fragment Length
D000348:Aflatoxins; D017931:DNA Primers