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Updated: Jul 18, 2026

Using Mycobacterium smegmatis as a Bioindicator for Zinc-Limited Growth Conditions in Mycobacteria
Published on: September 20, 2024
A fail-safe system for the ribosome under zinc-limiting conditions in Bacillus subtilis
Yousuke Natori1, Hideaki Nanamiya, Genki Akanuma
1Laboratory of Molecular Genetics and Research Information Center for Extremophile, College of Science, Rikkyo University, Toshima-ku Nishi-ikebukuro 3-34-1, Tokyo 171-8501, Japan.
Abstract:
As zinc is an essential trace metal ion for all living cells, cells elaborate a variety of strategies to cope with zinc starvation. In Bacillus subtilis, genes encoding ribosomal proteins L31 and S14 are duplicated into two types: one type contains a zinc-binding motif (RpmE or RpsN), whereas the other does not (YtiA or YhzA). We have previously shown that displacement of RpmE (L31) by YtiA from already assembled ribosomes is controlled by zinc, and this replacement could contribute to zinc mobilization under zinc-limiting conditions. We propose here that the switch between the two types of S14 has a different significance. rpsN is indispensable for growth and depletion of RpsN results in defective 30S subunits. YhzA can functionally replace RpsN to allow continued ribosome assembly under zinc-limiting conditions. Unlike YtiA, YhzA appeared in the ribosome at a slower rate consistent with incorporation into newly synthesized, rather than pre-existing ribosomes. These results raise the possibility that YhzA is involved in a fail-safe system for the de novo synthesis of ribosomes under zinc-limiting conditions.
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