Effect of gentian violet on the growth of the N and T RFLP types of the Aspergillus niger aggregate.
Taxa included in the Aspergillus niger aggregate are difficult to distinguish by phenotypic characterization. In this work, the effect of gentian violet on the growth of the N and T RFLP types of A. niger aggregate strains has been investigated. In total, 105 strains from different sources and origins, including reference cultures and field isolates were studied. Type N and T RFLP patterns, ochratoxin A production and the effect of different concentrations of gentian violet on the growth were determined in these strains. Forty nine strains belonged to the N type and 56 strains to the T type. Sixteen out of the 105 strains assayed were OTA producers. All the OTA-producing species belonged to the RFLP type N and none of the T type strains was able to produce OTA. Approximately 90% of the N type strains grew in the presence of 25 ppm of gentian violet. Only five N type strains did not grow on this medium. One of these strains was A. niger ATCC 22343, a well documented induced mutant strain and the remaining four strains belonged to the new species A. brasiliensis. On the contrary, all the T type strains failed to grow on this medium after 3 days of incubation (sensitivity 89.79%; specificity 100%). The use of growth in gentian violet as an additional character for classification and identification purposes in this taxonomic group may be useful because no phenotypic methods have yet been found that can distinguish between these species.
Veterinary Mycology Group, Department of Animal Health and Anatomy, Universitat Autònoma de Barcelona, Bellaterra, E-08193 Barcelona, Spain.
M Rosa
MR
Bragulat
F Javier
FJ
Cabañes
D001234:Aspergillus niger / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development*; D005840:Gentian Violet / Q000494:pharmacology*; D016533:Mycological Typing Techniques; D009793:Ochratoxins / Q000378:metabolism; D012150:Polymorphism, Restriction Fragment Length; D027843:Vitis / Q000382:microbiology
D009793:Ochratoxins; C025589:ochratoxin A; D005840:Gentian Violet