Botany and Microbiology Department, Faculty of Science (Boys), Al-Azhar University, The Permanent Camp St., 6th Ward, Nasr City, 11884, Cairo, Egypt.
BMC Microbiol. 2023 Mar 15;23(1):71. doi: 10.1186/s12866-023-02813-0.
Microfungal isolates were routinely identified depending on both macro and micro morphological characteristics, sometimes, some fungal isolates appeared to be similar and such cases caused severe confusion for mycologists during the preliminary identification. During our previous studies dealing with isolation of fungi for some biotechnological applications; two mystifying species Aspergillus flavus and Aspergillus oryzae showed similar cultural and macroscopic features. Therefore, the current study aimed to easily distinguish between these two species depending on simple approaches which are routinely followed by a large segment of researchers. Investigation of the macroscopic features was performed to check the fungal growth on four different media (PDA, MEA, YES, and CYA) followed by microscopic examination using an ordinary light microscope, and scanning electron microscope SEM. Also, screening of secondary metabolites for both strains was preliminarily identified to find out the difference between their metabolic profiles. Finally, ITS rDNA was involved to clarify the molecular differences along their partial sequence. Conclusively, the BLAST strategy confirmed the similarity of ITS rDNA segments of both fungal strains that supported our hypothesis. The color of the fungal growth is a very critical factor whereas it is extensively influenced by the type of cultivation media. Accordingly, the YES medium was an inspiring tool assisting in prompt differentiation during the culture investigation step whereas A. oryzae and A. flavus appeared significant mustard yellow and olive green respectively. During the microscopic examination, the CYA medium also had a robust effect on the formation of the conidial chain whereas the knit long chain was observed in A. oryzae while the conidia appeared scattered and not in a chain in the case of A. flavus. Likewise, both two strains possessed different metabolic profiles where A. oryzae is not an Afla toxin producer, unlike A. flavus.
从宏观和微观形态特征上，对分离出的微生物进行常规鉴定，有些时候，一些真菌分离株看起来很相似，这种情况会给真菌学家在初步鉴定时造成严重的混淆。在我们之前的一些涉及真菌分离的生物技术应用研究中；两株神秘的真菌，黄曲霉和米曲霉，表现出相似的培养和宏观特征。因此，本研究旨在根据广大研究人员常用的简单方法，轻松区分这两个物种。通过检查在四种不同培养基（PDA、MEA、YES 和 CYA）上的真菌生长情况来进行宏观特征研究，然后使用普通光学显微镜和扫描电子显微镜（SEM）进行微观检查。此外，对两种菌株的次级代谢产物进行了初步鉴定，以发现它们代谢谱之间的差异。最后，涉及 ITS rDNA 来阐明它们部分序列的分子差异。最终，BLAST 策略证实了两种真菌菌株 ITS rDNA 片段的相似性，这支持了我们的假设。真菌生长的颜色是一个非常关键的因素，而它受到培养介质类型的广泛影响。因此，YES 培养基是在培养调查步骤中进行快速区分的有力工具，而 A. oryzae 和 A. flavus 分别呈现出明显的芥末黄色和橄榄绿色。在显微镜检查中，CYA 培养基也对分生孢子链的形成有很强的影响，而在 A. oryzae 中观察到编织的长链，而在 A. flavus 中，分生孢子则呈分散状，不成链状。同样，两种菌株具有不同的代谢谱，A. oryzae 不像 A. flavus 那样是 Afla 毒素的产生者。
