Observations are presented showing that mature thalli of
the rumen anaerobic fungal isolate Neocallimastix frontalis strain
RE1 attach
to cellulose. This process and subsequent development of the
thalli have been studied. Thalli matured without attachment and then
attached directly by means of rhizoids to the surface of the
substrate. This process was quantified by the measurement of attachment
of
14C-radiolabelled fungal cells pregrown on
[UL-14C]-d-glucose to filter paper.
Washed cell suspensions were separated into
zoospores and thalli by filtration and the time-course of
attachment of each fraction to filter paper strips was determined. Both
thalli
and zoospores made a significant contribution to the colonization
process. It is suggested that the previously unrecognized ability of
mature thalli to attach to cellulose could be of importance in
the degradation of plant material in the rumen.
After attachment to filter paper the formation of dark brown
pigmented sporangia was observed after incubation for periods in
excess of 4 d. These had some similarities to resistant sporangia
which have been described in aerobic and anaerobic chytrids, but
they differed in some important respects. The pigmented cytoplasm
retracted, leaving a clear margin within an unthickened cell wall.
Histochemical tests showed that the pigment was not melanin and
strain RE1 was able to grow and form the pigment in the
presence of each of three inhibitors, tricyclazole, PP389 and
glyphosate, which block melanin biosynthesis pathways in fungi.