Spatial distribution and temporal variation of Microcystis species composition and microcystin concentration in Lake Biwa.

Spatial and temporal variation in Microcystis species composition and microcystin concentration, quantified by enzyme-linked immunosorbent assay and high-performance liquid chromatography, were investigated during a 3-year period (1998-2000) in the Northern Basin of Lake Biwa. The Northern Basin generally had a concentration of 5 microg L(-1) or less, except at station 1 (Nagahama Bay) from July to October during the study period. The maximum concentration at station 1 was 22.

Biosynthesis and transformation of homoanatoxin-a in the cyanobacterium Raphidiopsis mediterranea Skuja and structures of three new homologues.

The biosynthetic origin of the C-12 methyl group in homoanatoxin-a (1) was identified by the feeding experiment of L-[methyl-13C]-methionine in the culture of the cyanobacterium Raphidiopsis mediterranea Skuja strain LBRI 48. Remarkably high incorporation (80%) of 13C was observed at C-12. The in vivo enzymatic transformation of 1 was also examined by the prolonged culture of strain LBRI 48.

Reduction of germination frequency in Anabaena akinetes by sediment drying: a possible method by which to inhibit bloom formation.

The effect of desiccation on germination frequency of Anabaena akinetes was investigated to evaluate the practical usefulness of sediment drying in reservoirs as a measure of inhibition of Anabaena bloom formation. Sediment samples taken from a small reservoir, where an abundance of Anabaena blooms occur every summer were desiccated in the outdoors and in an incubator at 5, 10, 15, and 25 degrees C. As a result, the germination frequency of Anabaena akinetes was strongly inhibited in comparison with that of Anabaena akinetes preserved in a refrigerator without desiccation as a control.

Simultaneous production of homoanatoxin-a, anatoxin-a, and a new non-toxic 4-hydroxyhomoanatoxin-a by the cyanobacterium Raphidiopsis mediterranea Skuja.

A neurotoxin, homoanatoxin-a, was identified from a toxic strain of the cyanobacterium Raphidiopsis mediterranea Skuja (strain LBRI 48) isolated from Lake Biwa, Japan, as the major toxin component (0.57% of dry cell-weight). This cyanobacterium produced anatoxin-a and a new homoanatoxin-a derivative as minor components (0.