Citation:
Markus Schmidt-Heydt, Corinna E. Rufer, Ahmed Abdel-Hadi, Naresh Magan, Rolf Geisen. The production of aflatoxin B1 or G1 by Aspergillus parasiticus at various
combinations of temperature and water activity is related to the ratio of aflS
to aflR expression. Mycotoxin Research, Volume 26, Number 4, 2010, 241-246
Abstract:
The influence of varying combinations of wateractivity (aw) and temperature on
growth, aflatoxin biosynthesisand aflR/aflS expression of Aspergillus
parasiticuswas analysed in the ranges 17-42°C and 0.90-0.99 aw.Optimum growth
was at 35°C. At each temperature studied,growth increased from 0.90 to 0.99 aw.
Temperatures of 17and 42°C only supported marginal growth. The
externalconditions had a differential effect on aflatoxin B1 or G1biosynthesis.
The temperature optima of aflatoxin B1 andG1 were not at the temperature which
supported optimalgrowth (35°C) but either below (aflatoxin G1, 20-30°C) orabove
(aflatoxin B1, 37°C). Interestingly, the expression ofthe two regulatory genes
aflR and aflS showed anexpression profile which corresponded to the
biosynthesisprofile of either B1 (aflR) or G1 (aflS). The ratios of
theexpression data between aflS:aflR were calculated. Highratios at a range
between 17 and 30°C corresponded withthe production profile of aflatoxin G1
biosynthesis. A lowratio was observed at >30°C, which was related to aflatoxinB1
biosynthesis. The results revealed that the temperaturewas the key parameter for
aflatoxin B1, whereas it waswater activity for G1 biosynthesis. These
differences inregulation may be attributed to variable conditions of
theecological niche in which these specie
