Matsushima K, Yashiro K, Hanya Y, Abe K, Yabe K, Hamasaki T
Kikkoman Corporation, Noda-City, Japan.
Appl Microbiol Biotechnol. 2001 Jun;55(6):771-6. doi: 10.1007/s002530000524.
Ten strains isolated from industrial soy sauce producing koji mold were identified as Aspergillus sojae and distinguished from Aspergillus parasiticus morphologically and physiologically. There was no detectable aflatoxin in any culture extracts of A. sojae strains. Strain 477 was chosen as a representative strain of industrial A. sojae for further molecular analysis. All enzymatic activities associated with the aflatoxin biosynthesis were not detected or negligible in strain 477 compared with that of the A. parasiticus strain. Southern analysis suggested that the genomic DNA of strain 477 contained aflatoxin biosynthetic pathway genes. In contrast, all industrial strains lacked detectable transcripts of aflR, the main regulatory gene for aflatoxin biosynthesis, under the aflatoxin-inducing condition. Our data suggest that defects in aflR expression cause the lack of expression of aflatoxin-related genes which results in the absence of aflatoxin biosynthesis in A. sojae strains.
从用于生产工业酱油的米曲霉中分离出的十株菌株被鉴定为酱油曲霉，并在形态和生理上与寄生曲霉区分开来。在酱油曲霉菌株的任何培养提取物中均未检测到黄曲霉毒素。菌株477被选为工业酱油曲霉的代表性菌株进行进一步的分子分析。与寄生曲霉菌株相比，菌株477中未检测到或仅检测到可忽略不计的与黄曲霉毒素生物合成相关的所有酶活性。Southern分析表明，菌株477的基因组DNA包含黄曲霉毒素生物合成途径基因。相反，在黄曲霉毒素诱导条件下，所有工业菌株均缺乏黄曲霉毒素生物合成主要调节基因aflR的可检测转录本。我们的数据表明，aflR表达缺陷导致黄曲霉毒素相关基因表达缺失，从而导致酱油曲霉菌株中无黄曲霉毒素生物合成。
