Molecular Identification and Evaluation of Genetic Variability among Some Aflatoxigenic Aspergillus flavus Strains Isolated from Fish Feed in Egypt

AFLATOXINS are among the most potent carcinogenic, mutagenic and teratogenic natural compounds occurring in food and feed. In this study, molecular typing based on sequence variations in the ITS1-5.8S-ITS2 region was used to identify and genetically discriminate five selected strains of A. flavus, four strains (AUMC13909, AUMC13910, AUMC13911 and AUMC13917) were aflatoxigenic isolates recovered from fish feed. A. flavus AUMC10311 is a non-aflatoxigenic reference strain which was used as a negative control to investigate the molecular variability of the studied strains concerning their aflatoxigenic potential. The ITS data of the studied strains were submitted to NCBI GenBank with the accession numbers: MK491621, MK491622, MK491623, MK491624 and MK491625. Cluster analysis of these strains was performed depending on their ITS sequences, which discriminate them into three different sub-clusters. The highest genetic similarity (100%) was observed between AUMC13911 and AUMC10311. Proteins banding patterns of the examined strains were analyzed using SDS-PAGE, which resolved six polymorphic protein bands out of a total of 22 bands, ranged from 14 to 125kDa. Interestingly, a protein band (~ 40kDa) was relatively overexpressed in case of the aflatoxigenic strains while was hardly detected in the non-aflatoxigenic strain, suggesting that this protein might be involved in aflatoxin biosynthesis. Cluster analyses based on this banding pattern grouped the tested strains into two major clusters. The highest similarity index (97%) was between AUMC13911 and AUMC10311. These results confirmed the genetic variation among the examined A. flavus strains and the necessity for greater insight into cluster assembly using different Omics approaches.