It should best be formed in an environment containing an excess of an
external carbon and energy source. Macrae & Wilkinson (1958) have demonstrated
that organisms grown in a medium deficient in the carbon and energy
source had a poly-P-hydroxybutyrate content many times lower (e.g. about
four-fold) than organisms grown in a medium deficient in the nitrogen source
only. In the present experiments, it was found that in washed supension, a
carbon and energy source was partially assimilated into poly-P-hydroxybutyrate,
an assimilation which was prevented by 8:4-dinitrophenol. Under the
best conditions, the proportion of poly-P-hydroxybutyrate rose from 3 to
20% of the bacterial dry-weight in 4 hr. It is to be expected that themain
products of carbon assimilation will depend upon the nature of the carbon
source. Thus Dagley & Johnson (1953) showed that when Eschmichia coli was
grown on media containing different amounts of glucose and acetate, lipid
was formed best on media which contained an excess of acetate, while polysaccharide
was formed best on media which contained an excess of glucose.
Macrae & Wilkinson (1958) found that the presence of acetate in a glucosecontaining
medium yielded Bacillus megaterium in which the proportion of