Transertion provides evidence for coupling of transcription and translation in Bacillus subtilis

In Gram-negative bacteria, co-translational insertion of membrane proteins into the plasma membrane may be coupled to ongoing transcription, a phenomenon known as transertion. Transertion results in a physical shift of the coding gene from the nucleoid towards the membrane and is one of the determinants of the shape of the nucleoid and placement of cell division in Gram-negative bacteria. In contrast, the existence of functional coupling of transcription and translation in Bacillus subtilis and potentially other Gram-positive bacteria has been questioned, suggesting that transertion may not happen. Here, by imaging vertically oriented B. subtilis cells, we show that the gene of a transmembrane protein changes its localization from inside the nucleoid to the plasma membrane upon induction of its transcription. Localization is restored to the nucleoid when induction of transcription has ceased. The shift of the gene towards the membrane is strictly dependent on transcription, its induction, translation and transmembrane nature of the coded protein. These results suggest that, at least, some principles of cellular regulation based on functional coupling of transcription and translation may be conserved between Gram-positive and Gram-negative bacteria.