Interactions of Ribosomal Antibiotics and Informational Suppressors of Aspergillus nidulans

Strains of Aspergillus nidulans containing informational suppressors were grown on medium containing antibiotics known to affect protein synthesis at the ribosomal level. These strains reacted in the anticipated manner: presumed ribosomal suppressors suaA101, suaA105, suaC109 and sua-115 were sensitive or even hypersensitive to aminoglycoside antibiotics, whereas presumed tRNA-like suppressors suaB111, suaD103 and D108 were only slightly sensitive or wild-type in response. Hygromycin and paromomycin were the most useful antibiotics. All the antibiotics reduced the colony radial growth rate, K r, increased the lag phase and produced wrinkled morphology. Hygromycin was the most toxic. Resistant sectors were produced on paromomycin and hygromycin. The selective action of ‘misreading’ antibiotics on suaA and suaC strains is further evidence that these are ribosomal suppressors, whereas suaB and suaD may code for altered tRNA molecules. The results imply that hygromycin or paromomycin could be used for isolating ribosomal suppressors.