Background: Aspergillus niger ATCC® 16404TM is frequently used for quality control of various food, health and cosmetic products in industry. It is designated by several national and international standards organizations as a biological reference material. This strain manifests an unstable phenotype during sequential passages. The variable phenotype provides the degree of sensitivity needed to measure the quality and consistency of tested products. Significant phenotypic variations have been observed and may depend on the production processes and culture passages. To produce consistent, high-quality reference materials, we undertook further characterizations. Methods: The samples of seven batches from two sources were compared by genotyping (Rep-PCR barcoding and genomic ITS sequencing), phenotyping (Biolog(R) test kit), and morphological examinations of mycelia and fruiting structures. Results: The ITS sequences identified all seven batches as the same organism Aspergillus niger. The genomic DNA barcoding of the samples from the same source is nearly identical, but that of different sources revealed distinct patterns. Phenotypically, substrate utilization profiles are nearly identical among the batches from the same source, but showed clear variations among two different sources, particularly on several carbon substrates. Microscopically, the characteristics of the mycelia and conidial heads are very similar among all seven batches. However, the colony appearance differs significantly between two sources on SDA though it is almost same between batches of the same source. AST is being performed according to M38-A from CLSI/NCCLS. Conclusions/Discussions: Differences between two sample sources are quite striking with respect to molecular signatures, substrate utilization profiles, and colony morphology. However, the ITS sequences indicated that they are the same organism (species). The possibility that the original culture of A. niger was heterokaryonic is being investigated.
Full conference title:
47th Interscience Conference on Antimicrobial agents and Chemotherapy
- ICAAC 47th