The extremely halophilic actinomycete Actino-polyspora halophila is a rare
example of a heterotrophic eubacterium producing betaine from simple carbon
sources. A. halophila synthesized remarkably high intracellular concentrat
ions of betaine. The highest betaine concentration, determined at 24% (w/v)
NaCl, was 33% of the cellular dry weight. Trehalose was synthesized as a c
ompatible solute, accounting for up to 9.7% of the cellular dry weight. The
betaine concentration was shown to increase with increasing NaCl concentra
tion, whereas the trehalose concentration was highest at the lowest NaCl co
ncentration used (15% w/v). A. halophila was capable of accumulating betain
e from the medium, while at the same time betaine was also excreted back in
to the medium by the cells. Along with the de novo synthesis of betaine, A.
halophila was able to take up choline from the medium and oxidize it to be
taine. Some basic characteristics of the choline oxidation system are descr
ibed. Choline was oxidized to betaine aldehyde in a reaction in which H2O2
generation and oxygen consumption were coupled. Betaine aldehyde was also o
xidized, but with lesser efficiency. In addition, betaine aldehyde was oxid
ized further to betaine in a reaction in which NAD(P)(+) was reduced.