Cytochemical studies of cell viability and gene expression in Bacillus subtilis macrofibres

The viability of cells and the expression of a reporter gene in Bacillus subtilis macrofibres have been examined using cytochemical approaches. Previous studies have shown that macrofibres grow at an exponential rate in fluid environments and undergo complex dynamic motions as they elongate but the behaviour of individual cells in them has never been examined. A fluorescence staining procedure that distinguishes living cells from dead cells was used in the experiments described to examine cells in both left- and right-handed macrofibres. Very few dead cells were found in individual fibres. Their locations appeared to be random, suggesting that neither the extreme shape deformation imposed upon cells in the loop ends of fibres, nor the entrapment of cells in the interior of a fibre compromise viability. In related experiments, initial studies of reporter gene expression during fibre morphogenesis were conducted using a strain previously studied as conventional colonies. Spatial and temporal differences in the appearance of the blue cleavage product of X-Gal were found, suggesting that differential gene expression may arise in macrofibres in contrast to the results found in colonies. Two conclusions may be drawn from the findings: (i) virtually all cells in macrofibres are viable and (ii) all the cells in macrofibres do not always behave in an identical manner.