Aside from, the production of marcescins, S. marcescens
is unique among enteric bacteria in many respects.
It secretes extracellular chitinase; ' several proteases, a
nuclease and a lipase [25], and produces a wetting
agent or surfactant called 'serrawettin' which helps in
the colonisation of surfaces [26-281. In keeping with
its varied habitat, S. marcescens produces alternate
forms of differentially flagellate cells; these display
different types of motility depending on whether the
growth medium is liquid or solid [29]. Non-flagellate
cells of S. marcescens can also translocate efficiently
over the surface of low-agar media [30]. Matsuyama et
al. [31] showed that flagellate but. non-swarming dps
mutants of' S. marcescens with defects in serrawettin
production do not swarm on media solidified with
Difco agar. The spreading deficiency can be overcome
by serrawettin supplied extracellularly. Introduction of
flu defects into chemotaxis mutants does not affect this
mode of surface translocation.