Hm. Alvarez et al., Accumulation and mobilization of storage lipids by Rhodococcus opacus PD630 and Rhodococcus ruber NCIMB 40126, APPL MICR B, 54(2), 2000, pp. 218-223
The time course of the accumulation of triacylglycerols (TAGs) in Rhodococc
us opacus PD630 or of TAGs plus polyhydroxyalkanoates (PHA) in Rhodococcus
ruber NCIMB 40126 with gluconate or glucose as carbon source, respectively,
was studied. In addition, we examined the mobilization of these storage co
mpounds in the absence of a carbon source. R. opacus accumulated TAGs only
after the exhaustion of ammonium in the medium, and, with a fixed concentra
tion of the carbon source, the amounts of TAGs in the cells increased with
decreasing concentrations of ammonium in the medium. When these cells were
incubated in the absence of an additional carbon source, about 90% of these
TAGs were mobilized and used as endogenous carbon source, particularly if
ammonium was available. R. ruber accumulated a copolyester consisting of 3-
hydroxybutyrate and 3-hydroxyvalerate already during the early exponential
growth phase, whereas TAGs were synthesized and accumulated mainly during t
he late exponential and stationary growth phases. In the stationary growth
phase, synthesis of TAGs continued, whereas PHA was partially mobilized. In
the absence of an additional carbon source but in the presence of ammonium
, mobilization of TAGs started first and was then paralleled by the mobiliz
ation of PHA, resulting in an approximately 90% and 80% decrease of these s
torage compounds, respectively. During the accumulation phase, interesting
shifts in the composition of the two storage compounds occurred, indicating
that the substrates of the PHA synthase and the TAG synthesizing enzymes w
ere provided to varying extents, depending on whether the cells were in the
early or late exponential or in the stationary growth phase.