Ramijan, KarinaKarinaRamijanUltee, EvelineEvelineUlteeWillemse, JoostJoostWillemseZhang, ZherenZherenZhangWondergem, Joeri A.J.Joeri A.J.WondergemMeij, Anne van derAnne van derMeijHeinrich, DorisDorisHeinrichBriegel, ArianeArianeBriegelWezel, Gilles P. vanGilles P. vanWezelClaessen, DennisDennisClaessen2022-03-052022-03-052018https://publica.fraunhofer.de/handle/publica/25531810.1038/s41467-018-07560-9The cell wall is a shape-defining structure that envelopes almost all bacteria and protects them from environmental stresses. Bacteria can be forced to grow without a cell wall under certain conditions that interfere with cell wall synthesis, but the relevance of these wall-less cells (known as L-forms) is unclear. Here, we show that several species of filamentous actinomycetes have a natural ability to generate wall-deficient cells in response to hyperosmotic stress, which we call S-cells. This wall-deficient state is transient, as S-cells are able to switch to the normal mycelial mode of growth. However, prolonged exposure of S-cells to hyperosmotic stress yields variants that are able to proliferate indefinitely without their cell wall, similarly to L-forms. We propose that formation of wall-deficient cells in actinomycetes may serve as an adaptation to osmotic stress.enZellenActinobacteria666journal article