Prodigiosin biosynthesis in S. marcescens depends on
growth conditions [32]. Rjazantseva et al. [32] found
that pigment synthesis started later in the presence of low concentrations of NaCl, but that prodigiosin
accumulatiodbiomass unit was increased at NaCl
concentrations of up to 5% wlv. However, there was
no growth in a culture medium containing NaCl 8%
w/v. Visible light (2000 lux) influenced pigmentation
without changing the growth characteristics of the
culture. The maximum prodigiosin content in dark and
light cultures was observed on days 3-4 and 2-3,
respectively. The influence of illumination on pigmentation
of S. marcescens was also demonstrated. Light
affects the pigment synthesised by the culture directly.
Growing cells contain mono and dimer forms of
prodigiosin in glycerol, with light influencing these
pigments. The highest increase in biomass and
maximal pigmentation was found in cultures grown
on glycerol medium. A culture medium containing
glucose as the carbon and energy source did not allow
prodigiosin synthesis. The investigation supported the
conclusion that strains of S. marcescens differ in their
sensitivity to the effect of NaCl on prodigiosin
biosynthesis. Although proline was present ' in the
medium, S. marcescens grown on mineral media did
not produce pigment when the carbon source was
glucose or the nitrogen source was ammonium
chloride.
The pigment has a role in respiration [33] and has
some antibiotic properties [34]. It is presumed that
pigment biosynthesis acts as a protective mechanism
in unfavourable conditions when the growth of cells is
delayed [35]. While the utilisation of light energy by
pigmented S. marcexens has been suggested [32],
attempts to exploit the pigment as a commercial dye
have failed because of its sensitivity to light [36].
Pigment biosynthesis, as with other physiological
processes, is affected significantly by factors such as
temperature [37], ions [38], anionic detergents [39]
and amino acids [40]. However, most strains that
cause infection fail to produce pigment and form
colourless colonies which are difficult to distinguish
from other coliform organisms [41]; thus pigment
would not appear to be a virulence factor of advantage
to clinical isolates.