38
EDWARD C. CANTINO AND JAMES S. LOVETT
is not necessarily lacking but is simply elusive and/or cryptic. A very
real asset of R. rosea is its simple nutritional requirement (Stanier, 1942 ;
Whiffen, 1941 ; Smith and Lovett, unpublished) ; it needs only a carbon
source and some inorganic salts for growth. Haskins and Weston (1950)
reported that, with glucose as a carbon source, the fungus grew better in
the light than in the dark ; this raises obvious questions concerning the
function of its orange pigment. In another strain of the organism,
Cantino and Hyatt (1953c) concluded that the principal pigment was
gamma-carotene. Using more reliable and definitive chemical techniques,
Davies (1961a, b) recently suggested that Rhizophlyctis produces only
lycopene during its early stages (1 to 10 days) of growth, but that
gamma-carotene does accumulate later in development (10 to 21 days).
However, these results are difficult to interpret because the 21-day
growth period is many times greater than that necessary for this fungus
to complete a single generation (i.e., only 40 to 60 hours, depending upon
the carbon source provided; Smith and Lovett, unpublished data).
Thus, the changes observed by Davies may have been due, at least in
part, to the heterogeneity inherent in an aging multiple generation
culture (as was also used by Cantino and Hyatt); the results are
probably not (and certainly are not necessarily) reflections of stages in
the ontogeny of individual cells of Rhizophlyctis.
However, the means
are now at hand for obtaining unequivocal clarification of this point, for
techniques have been devised to obtain sufficiently large populations of
washed spores for growing synchronized cultures in a chemically defined
minimal medium (Smith and Lovett, unpublished data). It is now
evident that R. rosea can be added to the growing list of fungi useful for
experimental investigations of morphology.
C. Karlingia (Karlingiomyces) sp.
The taxonomic status of this chitinophilic aquatic mould is a matter
of some controversy (Karling, 1949; Sparrow, 1960); but the fungus,
unaware of its notoriety, goes on its way briskly degrading chitin from
almost any source. Although the creature is poorly understood, its
potential usefulness as an experimental guinea-pig is worth emphasizing.
In the asexual portion of its life-cycle, it greatly resembles
Rhizophlyctis.
It differs, however, in its possession of (a) fewer (but larger) lens-shaped
discharge papillae; (b) a lemon yellow pigmentation; and (c) a slightly
different method of spore discharge (the spores are quiescent for 10 to
15 seconds before swimming away). It differs greatly from R. rosea,
however, in its absolute requirement for either A^-acetylglucosamine or
chitin (Lovett, unpublished data), and its capacity to produce small
thick-walled resting spores. The latter, when mature, discharge via a
'prosporangium' in a manner analogous to that of
Rhizidiomyces
EDWARD C. CANTINO AND JAMES S. LOVETT
is not necessarily lacking but is simply elusive and/or cryptic. A very
real asset of R. rosea is its simple nutritional requirement (Stanier, 1942 ;
Whiffen, 1941 ; Smith and Lovett, unpublished) ; it needs only a carbon
source and some inorganic salts for growth. Haskins and Weston (1950)
reported that, with glucose as a carbon source, the fungus grew better in
the light than in the dark ; this raises obvious questions concerning the
function of its orange pigment. In another strain of the organism,
Cantino and Hyatt (1953c) concluded that the principal pigment was
gamma-carotene. Using more reliable and definitive chemical techniques,
Davies (1961a, b) recently suggested that Rhizophlyctis produces only
lycopene during its early stages (1 to 10 days) of growth, but that
gamma-carotene does accumulate later in development (10 to 21 days).
However, these results are difficult to interpret because the 21-day
growth period is many times greater than that necessary for this fungus
to complete a single generation (i.e., only 40 to 60 hours, depending upon
the carbon source provided; Smith and Lovett, unpublished data).
Thus, the changes observed by Davies may have been due, at least in
part, to the heterogeneity inherent in an aging multiple generation
culture (as was also used by Cantino and Hyatt); the results are
probably not (and certainly are not necessarily) reflections of stages in
the ontogeny of individual cells of Rhizophlyctis.
However, the means
are now at hand for obtaining unequivocal clarification of this point, for
techniques have been devised to obtain sufficiently large populations of
washed spores for growing synchronized cultures in a chemically defined
minimal medium (Smith and Lovett, unpublished data). It is now
evident that R. rosea can be added to the growing list of fungi useful for
experimental investigations of morphology.
C. Karlingia (Karlingiomyces) sp.
The taxonomic status of this chitinophilic aquatic mould is a matter
of some controversy (Karling, 1949; Sparrow, 1960); but the fungus,
unaware of its notoriety, goes on its way briskly degrading chitin from
almost any source. Although the creature is poorly understood, its
potential usefulness as an experimental guinea-pig is worth emphasizing.
In the asexual portion of its life-cycle, it greatly resembles
Rhizophlyctis.
It differs, however, in its possession of (a) fewer (but larger) lens-shaped
discharge papillae; (b) a lemon yellow pigmentation; and (c) a slightly
different method of spore discharge (the spores are quiescent for 10 to
15 seconds before swimming away). It differs greatly from R. rosea,
however, in its absolute requirement for either A^-acetylglucosamine or
chitin (Lovett, unpublished data), and its capacity to produce small
thick-walled resting spores. The latter, when mature, discharge via a
'prosporangium' in a manner analogous to that of
Rhizidiomyces