The internal cell wall structure of the bacterium Lactobacillus helveticus has been observed in situ in aqueous solution using an atomic force microscope (AFM). The AFM tip was used not only for imaging but presumably to remove mechanically large patches of the outer cell wall after appropriate chemical treatment, which typically leaves the bacteria alive. The surface exposed after such a surgery revealed ca. 26 nm thick twisted strands within the cell wall. The structure and location of the observed strands are consistent with the glycan backbone of peptidoglycan fibers that give strength to the cell wall. The found structural organization of these fibers has not been observed previously.
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