Cleveland T E, Bhatnagar D, Brown R L
Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana 70124.
Appl Environ Microbiol. 1991 Oct;57(10):2907-11. doi: 10.1128/aem.57.10.2907-2911.1991.
Cofermentation of Aspergillus parasiticus strains (SRRC 163 and SRRC 2043) blocked at different steps in the aflatoxin B1 (AFB1) biosynthetic pathway in a synthetic liquid medium or on seeds (cottonseed, corn kernels, and peanuts) resulted in production of AFB1. Strain SRRC 2043 accumulated O-methylsterigmatocystin (OMST), a late precursor in AFB1 biosynthesis, whereas SRRC 163 accumulated averantin, an early precursor in the pathway. Strain SRRC 2043 secreted large amounts of OMST in culture relative to the amounts of several other pathway intermediates secreted into media (by other AFB1 pathway-blocked strains). AFB1 production occurred even when colonies of SRRC 163 and SRRC 2043 strains (producing no detectable AFB1) were grown together on an agar medium while physically separated from each other by a filter membrane (0.22-micron pore size). In addition, when mycelia of strain SRRC 163 were added to culture filtrates (containing no mycelia but containing secreted OMST) of strain SRRC 2043, AFB1 production occurred. The results suggested a chemical (rather than genetic) mechanism of complementation for AFB1 production between AFB1 pathway-blocked strains, since no mycelial contact was required between these strains for AFB1 production. The mechanism for chemical complementation involves secretion of OMST by SRRC 2043 and subsequent absorption and conversion of OMST to AFB1 by mycelia of strain SRRC 163.
在合成液体培养基中或在种子（棉籽、玉米粒和花生）上，对黄曲霉毒素B1（AFB1）生物合成途径中不同步骤受阻的寄生曲霉菌株（SRRC 163和SRRC 2043）进行共发酵，结果产生了AFB1。菌株SRRC 2043积累了O-甲基柄曲霉素（OMST），它是AFB1生物合成中的晚期前体，而SRRC 163积累了柄曲菌素，它是该途径中的早期前体。相对于分泌到培养基中的其他几种途径中间体的量（由其他AFB1途径受阻菌株分泌），菌株SRRC 2043在培养物中分泌了大量的OMST。即使SRRC 163和SRRC 2043菌株（不产生可检测到的AFB1）的菌落通过滤膜（孔径0.22微米）彼此物理分离地在琼脂培养基上一起生长时，也会产生AFB1。此外，当将菌株SRRC 163的菌丝体添加到菌株SRRC 2043的培养滤液（不含菌丝体但含有分泌的OMST）中时，会产生AFB1。结果表明，AFB1途径受阻菌株之间产生AFB1的互补机制是化学（而非遗传）机制，因为这些菌株之间产生AFB1不需要菌丝体接触。化学互补机制涉及SRRC 2043分泌OMST，随后菌株SRRC 163的菌丝体将OMST吸收并转化为AFB1。
