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J. Bacteriol., Feb 1997, 1186-1192, Vol 179, No. 4
YI Park, ML Buszko and JE Gander
Penicillium fellutanum produces a phosphorylated, choline-containing
extracellular polysaccharide, peptidophosphogalactomannan (pP(x)GM) [where
x is the number of phosphodiester residues]). The 13C-methyl- labeled
pP(x)GM ([methyl-13C]pP(x)GM) was prepared from the cultures supplemented
with L-[methyl-13C]methionine and was used as a probe to monitor the fate
of phosphocholine in this polymer. The addition of [methyl-13C]pP(x)GM to
growing cultures in low-phosphate medium resulted in the disappearance
within 5 days of [methyl- 13C]phosphocholine and
N,N'-dimethylphosphoethanolamine from the added [methyl-13C]pP(x)GM. Two
13C-methyl-enriched cytoplasmic solutes, choline-O-sulfate and glycine
betaine, were found in mycelial extracts, suggesting that
phosphocholine-containing extracellular pP(x)GM of P. fellutanum is a
precursor of intracellular choline-O-sulfate and glycine betaine. The
mycelia cultured in low-phosphate (2 mM) medium contained glycine betaine
and 1.5-fold more choline-O-sulfate than those grown in high-phosphate (20
mM) medium. The high levels of extracellular nonspecific
phosphocholine:phosphocholine hydrolase and acid phosphomonoesterase
observed in the low-phosphate culture medium are likely related to the
release of phosphocholine from pP(x)GM and hydrolysis of phosphocholine,
respectively. These results suggest that extracellular pP(x)GM of P.
fellutanum provides phosphate needed as the environment becomes depleted of
this nutrient. Choline, in excess of that needed immediately, is stored in
the cytoplasm in forms that can be reutilized.
Copyright © 1997, American Society for Microbiology
Utilization of phosphocholine from extracellular complex polysaccharide as a source of cytoplasmic choline derivatives in Penicillium fellutanum
Department of Microbiology and Cell Science, University of Florida, Gainesville 32611-0700, USA.
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