Abstract
Antibiotic-independent revertants of an erythromycin-dependent strain of Escherichia coli were isolated by spontaneous selection. Their ribosomal proteins were analyzed by two-dimensional polyacrylamide gel electrophoresis. In contrast to most ribosomally targeted selections, the specific absence of a certain protein from the ribosome, rather than alterations in ribosomal proteins, was observed. Mutants were found with protein S20, L11, L15, L28, L29, or L30 missing.