Microbiology Research Laboratory, Post Graduate Department of Zoology, Molecular Biology and Genetics, Presidency University, 86/1, College Street, Kolkata, 700 073 India.
Indian J Microbiol. 2012 Jun;52(2):215-21. doi: 10.1007/s12088-011-0197-z. Epub 2011 Aug 26.
Rhizopus oryzae PR7 MTCC 9642 was a dimorphic fungus that showed a regular 90 days cycle of filament (mycelium) to pellet (yeast) transformation through a distinct bottom dwelling intermediate state and the pellets never revert back to filamentous form. Apart from the normal cycle, high temperature (37°C and above) and extreme pH also induced the yeast formation. Among the ions tested, calcium and chloride ions were found to restore the filamentous morphology, even in extreme pH and temperature. Cysteine HCl also played noteworthy role in maintaining mycelial growth even at adverse condition. Immobilized spores showed the appearance of intermediate form instead of typical yeast form even at high temperature. The strain could produce a number of extracellular hydrolytic enzymes like cellulolytic, xylanolytic, pectinolytic and amylolytic enzymes. The pellet and mycelial forms were found to be a better producer of cellulase-lignocellulase enzymes and amylolytic enzymes respectively, which might be correlated with their infectivity. Increase in inoculum size, agitation during cultivation, change in carbon and nitrogen source failed to induce mycelial growth in extreme conditions, which might be explained as irreversible change of configuration of protein responsible for mycelial development.
米根霉 PR7 MTCC 9642 是一种二相真菌，通过明显的底层栖息中间状态，呈现出规则的 90 天丝状（菌丝体）到颗粒（酵母）转化周期，颗粒体从不恢复为丝状形态。除了正常周期外，高温（37°C 及以上）和极端 pH 值也会诱导酵母形成。在测试的离子中，发现钙离子和氯离子能够恢复丝状形态，即使在极端 pH 值和温度下也是如此。盐酸半胱氨酸在恶劣条件下也能发挥重要作用，维持菌丝体生长。固定化孢子即使在高温下也表现出中间形态，而不是典型的酵母形态。该菌株可以产生许多细胞外水解酶，如纤维素酶、木聚糖酶、果胶酶和淀粉酶。颗粒体和菌丝体形式分别被发现是纤维素酶-木质纤维素酶和淀粉酶的更好产生者，这可能与其感染力有关。增加接种量、培养过程中的搅拌、改变碳源和氮源都未能在极端条件下诱导菌丝体生长，这可能是由于负责菌丝体发育的蛋白质结构的不可逆变化所解释。
