||Bacteria Escherichia coli
||Fegatella F., Lim J., Kjelleberg S., Cavicchioli R. Implications of rRNA operon copy number and ribosome content in the marine oligotrophic ultramicrobacterium Sphingomonas sp. strain RB2256. Appl Environ Microbiol. 1998. 64(11):4433-4438. p.4434 right column paragraph above bottom paragraph & p.4435 table 1PubMed ID9797303
||Kiss et al. The number of rRNA genes in Escherichia coli. 1977. FEBS Lett. 79:77-79PubMed ID330226
||"rRNA operon copy number was determined by Southern hybridization with a 16S ribosomal DNA probe hybridized to restriction enzyme digests of genomic DNAs from RB2256 and control strains:E. coli, V. fischeri, V. harveyi, and M. pneumoniae (Fig. 1)."
||"For all control strains, the number of bands present was consistent with the number of rRNA operons known to be present in those organisms (Table 1). For example, E. coli possesses seven rRNA operons (primary source) and six or seven bands were detected, and M. pneumoniae possesses one to two rRNA operons (ref 1) and two bands were detected."