Comparative ecophysiology and genomics of the toxic unicellular alga Fibrocapsa japonica

P>Ten axenic cultures, referred to as Fibrocapsa japonica, were studied for their morphology, pigment composition, toxicity and phylogeny. Morphologically, all 10 accessions were similar and displayed equivalent pigment contents. We identified chlorophylls a and c, beta-carotene and fucoxanthin as the dominant pigments, together with xanthophyll cycle carotenoids likely to be involved in photoprotection. All 10 accessions caused brine shrimp, Artemia salina, mortality and displayed haemolytic and haemaglutination activities toward sheep erythrocytes. Our results indicate that haemaglutination activity is a key component of F. japonica toxicity. Examination of a collection of F. japonica expressed sequence tags (ESTs) has led to the identification of candidate genes involved in F. japonica toxicity and/or growth control.