Effect of hypertonic solutes upon the polysaccharide capsule in Cryptococcus neoformans.
The polysaccharide capsule is a characteristic virulence factor in the yeast-pathogen, Cryptococcus neoformans. Growth in hypertonic growth media results in yeast cells with visibly smaller capsules. We investigated this suppression quantitatively, using a chemical assay for cell-bound and dissolved capsular polysaccharide. Molar NaCl suppressed production of cell-bound polysaccharide by a factor of 2.5- to 5-fold. The possibility of salt-induced physico-chemical contraction of capsular gel was tested by dialysis of fixed cells from hypotonic medium against medium containing 1 M NaCl and against the original medium again, while capsular thickness, packed cell volume and cell-bound polysaccharide were followed. We detected a physical contraction of gel following dialysis against medium containing 1 M NaCl. Mutants which gave mucoid colonies on hypertonic agar were isolated. One of these gave twice as much polysaccharide as the wild type when cultivated in medium containing 1 M NaCl. The hypercapsular trait was passed through serial outcrosses to the wild type and segregated as a chromosomal gene. This mutant may represent a gene which regulates production of capsular polysaccharide.
Jacobson
E S
ES
Tingler
M J
MJ
Quynn
P L
PL
D003454:Cryptococcus / Q000254:growth & development*; D003455:Cryptococcus neoformans / Q000235:genetics / Q000254:growth & development*; D003470:Culture Media; D009154:Mutation; D010641:Phenotype; D011134:Polysaccharides / Q000378:metabolism*; D012462:Saline Solution, Hypertonic
D003470:Culture Media; D011134:Polysaccharides; D012462:Saline Solution, Hypertonic