Filament formation in Thermus species in the presence of some D-amino acids or glycine.

A number of strains of Thermus spp. changed morphology from rods of about 6 to 8 microns long to multicellular filaments (unsheathed trichomes) up to many hundreds of micrometres long with the addition of glycine or certain D-amino acids to the growth medium. Associated with this change was the formation of braided trichomes and occasionally true knots. Filament formation was reversible by the removal of the causal agent, but only if growth was possible. Electron microscopy suggested that the wall structure was not changed, but only that cells did not separate due to the continuous nature of the outer membrane layer. The filaments were thus multicellular. The constituent cells were similar in length to the normal rod-shaped cells. Filament formation by Thermus spp. may have applications in industrial scale culture of these extracellular enzyme-producing thermophilic bacteria.