title: Growth and sporulation defects in Bacillus subtilis mutants with a single rrn operon can be suppressed by amplification of the rrn operon.
abstract: The genome of Bacillus subtilis strain 168 encodes ten rRNA (rrn) operons. We previously reported that strains with only a single rrn operon had a decreased growth and sporulation frequency. We report here the isolation and characterization of suppressor mutants from seven strains that each have a single rrn operon (rrnO, A, J, I, E, D or B). The suppressor mutants for strain RIK656 with a single rrnO operon had a higher frequency of larger colonies. These suppressor mutants had not only increased growth rates, but also increased sporulation frequencies and ribosome levels compared to the parental mutant strain RIK656. Quantitative PCR analyses showed that all these suppressor mutants had an increased number of copies of the rrnO operon. Suppressor mutants were also isolated from the six other strains with single rrn operons (rrnA, J, I, E, D or B). Next generation and capillary sequencing showed that all of the suppressor mutants had tandem repeats of the chromosomal locus containing the remaining rrn operon (amplicon). These amplicons varied in size from approximately 9 to 179 kb. The amplifications were likely to be initiated by illegitimate recombination between non- or micro-homologous sequences, followed by unequal crossing-over during DNA replication. These results are consistent with our previous report that rrn operon copy number has a major role in cellular processes such as cell growth and sporulation.
authors.affiliation: Department of Life Science and Research Center for Life Science, College of Science, Rikkyo University, Toshima-ku Nishi-ikebukuro 3-34-1, Tokyo 171-8501, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Yano
authors.affiliation: Department of Life Science and Research Center for Life Science, College of Science, Rikkyo University, Toshima-ku Nishi-ikebukuro 3-34-1, Tokyo 171-8501, Japan.
authors.forename: Kenta
authors.initials: K
authors.lastname: Masuda
authors.affiliation: Department of Life Science and Research Center for Life Science, College of Science, Rikkyo University, Toshima-ku Nishi-ikebukuro 3-34-1, Tokyo 171-8501, Japan.
authors.forename: Genki
authors.initials: G
authors.lastname: Akanuma
authors.affiliation: Department of Life Science and Research Center for Life Science, College of Science, Rikkyo University, Toshima-ku Nishi-ikebukuro 3-34-1, Tokyo 171-8501, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Wada
authors.affiliation: Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Setagaya-ku, Sakuragaoka 1-1-1, Tokyo 156-8502, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsumoto
authors.affiliation: Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Setagaya-ku, Sakuragaoka 1-1-1, Tokyo 156-8502, Japan.
authors.forename: Yuh
authors.initials: Y
authors.lastname: Shiwa
authors.affiliation: Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Setagaya-ku, Sakuragaoka 1-1-1, Tokyo 156-8502, Japan.
authors.forename: Taichiro
authors.initials: T
authors.lastname: Ishige
authors.affiliation: Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Setagaya-ku, Sakuragaoka 1-1-1, Tokyo 156-8502, Japan.|Department of Bioscience, Tokyo University of Agriculture, Setagaya-ku, Sakuragaoka 1-1-1, Tokyo 156-8502, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yoshikawa
authors.affiliation: Microbial Genetics Laboratory, Genetic Strains Research Center, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan.|Department of Genetics, Graduate University for Advanced Studies, Sokendai, 1111 Yata, Mishima, Shizuoka 411-8540, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Niki
authors.affiliation: Microbial Function Laboratory, National Food Research Institute, National Agriculture Research Organization, Tsukuba-shi Kannondai 2-1-12, Ibaraki 305-8642, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Inaoka
authors.affiliation: Department of Life Science and Research Center for Life Science, College of Science, Rikkyo University, Toshima-ku Nishi-ikebukuro 3-34-1, Tokyo 171-8501, Japan.
authors.forename: Fujio
authors.initials: F
authors.lastname: Kawamura
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D005784:Gene Amplification; D018628:Gene Dosage; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D009876:Operon; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism; D013171:Spores, Bacterial / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins