Absence of 3′-Terminal Residues from Transfer Ribonucleic Acid of Dormant Spores of Bacillus megaterium

Abstract

Essentially all (>97%) of the transfer ribonucleic acid (tRNA) in log-phase and sporulating cells of Bacillus megaterium contains a complete 3′-cytidyl-cytidyl-adenosine terminus. However, about one-third of the tRNA in the dormant spore lacks the 3′-terminal adenosine 5′-monophosphate (AMP) residue, and some of the adjacent cytosine monophosphate residues are also missing. Examination of specific tRNAs indicated that those specific for isoleucine, leucine, and methionine are missing 30 to 40% of their terminal residue, whereas tRNAs specific for tyrosine lack 88% of the 3′-terminal AMP. Defective spore tRNA is not degraded during germination, but the missing residues are added back in the first minutes of the process. The enzyme catalyzing the addition reaction, tRNA nucleotidyltransferase, is present in the dormant spore at a level similar to that found in the vegetative cell.