RT Journal Article SR Electronic(1) A1 Yano, Koichi A1 Wada, Tetsuya A1 Suzuki, Shota A1 Tagami, Kazumi A1 Matsumoto, Takashi A1 Shiwa, Yuh A1 Ishige, Taichiro A1 Kawaguchi, Yasuhiro A1 Masuda, Kenta A1 Akanuma, Genki A1 Nanamiya, Hideaki A1 Niki, Hironori A1 Yoshikawa, Hirofumi A1 Kawamura, FujioYR 2013 T1 Multiple rRNA operons are essential for efficient cell growth and sporulation as well as outgrowth in Bacillus subtilis JF Microbiology, VO 159 IS Pt_11 SP 2225 OP 2236 DO https://doi.org/10.1099/mic.0.067025-0 PB Microbiology Society, SN 1465-2080, AB The number of copies of rRNA (rrn) operons in a bacterial genome differs greatly among bacterial species. Here we examined the phenotypic effects of variations in the number of copies of rRNA genes in the genome of Bacillus subtilis by analysis of eight mutant strains constructed to carry from two to nine copies of the rrn operon. We found that a decrease in the number of copies from ten to one increased the doubling time, and decreased the sporulation frequency and motility. The maximum levels for transformation activity were similar among the strains, although the competence development was significantly delayed in the strain with a single rrn operon. Normal sporulation only occurred if more than four copies of the rrn operon were present, although ten copies were needed for vegetative growth after germination of the spores. This behaviour was seen even though the intracellular level of ribosomes was similar among strains with four to ten copies of the rrn operon. Furthermore, ten copies of the rrn operon were needed for the highest swarming activity. We also constructed 21 strains that carried all possible combinations of two copies of the rrn operons, and found that these showed a range of growth rates and sporulation frequencies that all fell between those recorded for strains with one or three copies of the rrn operon. The results suggested that the copy number of the rrn operon has a major influence on cellular processes such as growth rate and sporulation frequency., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.067025-0