Specific polar localization of ribosomes in Bacillus subtilis depends on active transcription

The large subunit of ribosomes in Bacillus subtilis was tagged by generatio n of a fusion of ribosomal protein Ll to blue fluorescent protein (BFP). Th e fusion was fully active and localized around the nucleoids, predominantly close to the cell poles, in growing cells. However, in stationary phase ce lls, and in growing cells treated with rifampicin, L1-BFP was distributed t hroughout the cells, in contrast to cells treated with chloramphenicol, in which ribosomes still localized around nucleoids. These data show that spec ific localization of ribosomes is not due to nucleoid exclusion, but is a d ynamic process due to active synthesis of RNA. Dual labelling of ribosomes and cold shock proteins (CSPs) tagged with green fluorescent protein (GFP) revealed colocalization of both protein classes. CSPs are implicated in cou pling of transcription with translation and may bridge the spatial separati on of ribosomes and nucleoid-associated RNA polymerase.