For example, one of the authors has argued that the word ‘pathogen’ is limiting our understanding of microbial pathogenesis and may even be hindering progress in the field ( Casadevall and Pirofski, 2014). However, words can also be limiting when used to refer to complex topics in topics. The way we use words shapes our thoughts and actions. In sum, S-cells may represent a newly identified developmental stage that enables actinomycetes to thrive under hyperosmotic stress conditions.Words matter for they are essential to the symbolic communication that is unique to our species. Finally, following prolonged exposure to osmotic stress, some cells acquire mutations and convert into L-forms that can proliferate indefinitely in the cell wall-deficient state. This cell wall-deficient state is transient as S-cells can switch to the canonical mycelial growth mode, although those switched colonies exhibit developmental defects. S-cells extrude from the hyphal tips into the environment, contain DNA and are larger than 2 µm in size (distinguishing them from spores).

Formation of S-cells seems to be common in filamentous bacteria, as they occur in Streptomyces and Kitasatospora species in response to hyperosmotic stress.

Claessen and colleagues now report that when filamentous actinomycetes are exposed to osmotic stress they extrude previously undetected cell wall-deficient cells, which they termed S-cells. Bacterial variants that lack a cell wall are known as L-forms and can be induced under conditions that interfere with cell wall synthesis.

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