Thickened cell wall and aberrant septa in the calcineurin mutants. The wild type and the calcineurin mutants were grown in GMM broth for a period of 48 h at 37°C and processed for transmission electron microscopy as mentioned in experimental procedures. Arrowheads indicate the irregular septa and dotted arrows indicate the thickening of the cell walls and the extracellular fibrous material. Magnification for panels A, D, E, G, H, J is 12,000X, for panels M and K it is 5000X, for panels B and N it is 30,000X and for panels C, F, I, L and O it is 50,000X.