Chitin in the symbiotic protist Nephromyces

The endosymbiotic marine protist Nephromyces was first classified as a chytridiomycete by Giard in 1888, yet its taxonomic affinities with chytridiomycetes, as well as with other groups traditionally considered fungi, remain in doubt. To supplement the morphological data on which taxonomic inferences have been based, we assayed Nephromyces for chitin, using three methods: chromatographic assays of acid hydrolysates of alkali-resistant cell residues; infrared spectral analysis; and observations of N-acetylglucosamine-specific lectin-binding properties of the surfaces of living cells. All three assays indicate the presence of chitin in Nephromyces. The possible phylogenetic implications of this finding are discussed.