Twisted states of Bacillus subtilis macrofibers reflect structural states of the cell wall

Static and dynamic studies of helical Bacillus subtilis macrofibers reveal that a spectrum of twisted states exists ranging from tight left-handed structures with twist equal to approximately equal to 40 left turns per mm to tight right-handed structures with twist equal to 57 right turns per mm. In the lytic-deficient strain FJ7 , twist varies as a function of growth temperature above or below 39 degrees C, where there is zero twist. The relationship between the temperature (below 39 degrees C) at which right-hand structures are produced to the time it takes for them to begin the inversion process in which they become left-handed following transfer to 48 degrees C reveals that structures with less twist are more rapidly converted to left-handedness than are those with higher values of twist. The initial response of live macrofibers to digestion by lysozyme consists of "relaxation" motions in which the twist of both left- and right-handed structures changes towards the right-hand end of the spectrum. The rate of relaxation is approximately equal to 5-fold higher at the left-hand end than at the right-hand end. These findings suggest that cell wall polymers can assume a range of structural states during helical growth and that these determine the quantitative aspects of macrofiber shape as well as the sensitivity of walls to attack by lysozyme.