banana-white and grey-white in colour (Strzelczyk et al.,
1999). Among others, pale violet, grey and beige actinomycetes
cause biodeterioration of paper. The nature of
dyeing by actinomycetes can often be used as index of
the species involved. Bleaching stains in an acid medium,
often practised in conservation of historic objects, may
cause the stains to disappear for some time, but they
can appear again after the bleaching substance has been
washed away. Many of the actinomycete dyes are antibiotic,
and not infrequently, e.g. on deteriorated parchment,
sites from which other microorganisms are excluded by
antibiotic action are seen as clear circles on the deteriorated
surface.