their natural environment (the sponge mesohyl) and/or may not contain the molecular
growth factors needed to induce mitosis. Although some response to mammalian growth
factors has been found, sponge cells may have their own, specific growth factors, which
remain to be identified. It has been demonstrated that the lack of cell-to-cell contact after
artificial dissociation of sponge tissue considerably reduces the high telomerase activity
of the cells, indicating that the loss of proliferative capacity is caused by dissociation.
Although the exact mechanism is unknown, cell-to-cell contact or cell-to-matrix contact
apparently stimulates the production of growth factors and telomerase (Custodio et al.,
1998; Koziol et al., 1998).
With respect to the facts and hypotheses mentioned above, the potential way to
improve sponge cell-culture techniques is by growing sponge cells as axenic,
multicellular aggregates formed from suspended sponge cells after treatment with
antibiotics and antimycotica. Cell-to-cell contact is then restored, thus re-initiating the
processes of mitosis and growth.
Two possibilities are presently in study in our group: growth of sponges as
primmorphs and growth of immobilised sponge cells. In both cases sponge cells are
grown as cells with cell-to-cell contact. The present state of this novel research is
described below. It should be remembered that developments in sponge-cell cultivation
are in an initial phase. It is difficult to draw general conclusions about applicability and
feasibility in these circumstances.
PRIMMORPHS
Growing sponges as axenic, multicellular aggregates has been attempted. To obtain such
aggregates, sponges are first dissociated in CMF-ASW and treated with antibiotics. If the
dissociated cells are then transferred back into normal seawater (with antibiotics), they
will reaggregate and form spherical clumps of cells (primmorphs) within a few weeks
(Custodio et al., 1998; Müller 1998). The formation of these primmorphs is illustrated for
Stylissa massa (Figure 17.4). If a cell suspension of Stylissa massa is shaken gently, after
only a few hours the cells start to reaggregate (Figure 17.5A). After a few days the
aggregates becomes smoother (Figure 17.5B) and after 11 days strong smooth spherical
Marine sponges as biocatalysts 515