In Bacillus subtilis, a distinct chained-rod morphology
is associated with a population of cells known to produce
ECM and to remain attached to the surface, while
short unchained rods express flagellar components and
are motile [99]. Here, we identified a population of
surface-attached cellular structures appearing during biofilm
formation and present within developing biofilms but
never in planktonic culture (Figure 3; see also Additional
file 1: Figure S2 and Additional file 2: Movie 1). Long rodstructures were confirmed as live cells, as the only source
of fluorescent signal in Figure 3B,C,D was endogenous
GFP. This morphotype is unlikely to be the result of a
spontaneous mutation in the H1206(pJAM1020) strain;
it was observed in several independent strains and
Haloferax species are known to have a low spontaneous
mutation rate [100].