Inhibition of Chlorella growth by degradation and related products of linoleic and linolenic acids and the possible significance of polyunsaturated fatty acids in phytoplankton ecology

The activity of the degradation products of linoleic and linolenic acids in inhibiting the growth of the green alga Chlorella pyrenoidosa was determined using the paper disk-agar plate method. Although hydroperoxides derived from these acids and aldehyde biodegradation products and other related aldehydes and alcohols showed inhibitory activity, it is concluded from the weakness of the activities that the inhibitory effects of polyunsaturated fatty acids(PUFAs) on Chlorella growth is due mainly to the acids themselves and not their degradation products. The evidence for the possible ecological role of PUFAs as toxic agents against phytoplankton is presented

Activity of cyanobacterial and algal odor compounds found in lake waters on green alga Chlorella pyrenoidosa growth

Volatile organic compounds produced by cyanobacteria and algae in freshwater lakes and contributing to the odour of lakes were tested for their ability to inhibit the growth of the green alga Chlorella pyrenoidosa by the paper disk-agar plate method. Geosmin, beta -cyclocitral, alpha- and beta -ionones, and geranylacetone exhibited inhibitory activity by diffusion in the 2-5 mg ml(-1) range. alpha- and beta -Ionones and geranylacetone showed inhibition through the vapor phase at 10 mg ml(-1). Dimethyl disulfide showed no inhibition at 10 mg ml(-1). The norcarotenoids, which are prominent contributors to the odour of lake waters, were not significantly active in inhibiting the growth of Chlorella, with activity in the same range as monoterpene alcohols in general

Purification of Aphanizomenon flos-aquae toxin and its chemical and physiological properties

A toxin in chromatographically pure form has been isolated from natural blooms of the blue-green alga Aphanizomenon flos-aquae. The toxin is a strongly basic substance, which gives a positive ninhydrin reaction and appears to be a guanidine derivative. A dose of 2·7 μg injected intraperitoneally into 20 g mice caused death in 4·9 min. The purified toxin reversibly blocks action potentials and tension development in amphibian nerve-muscle preparations without alteration of the resting potential. The toxin differs from saxitoxin in some of its chemical and physical properties, and some of its effects on neuromuscular systems

Pterins of the cyanobacterium Aphanizomenon flos-aquae

The cyanobacterium Alphanizomenon flos-aquae contains various glycosides of a pterin that had previously been tentatively identified as 6-(threo-1,2-dihydroxypropyl)-pterin. The pterin is now identified as 6-(l-threo-1,2-dihydroxypropyl)pterin(6-l-threo-biopterin) by NMR and mass spectrometry, thinchromatographic comparisons with authentic samples and by optical rotation. The 6-l-threo-biopterin glycoside-1 from toxic strain NH-1 gave rise to xylose and glucose on hydrolysis, whereas its glycoside-2 from Cambridge Collection and nontoxic NH-1 strains gave mannose and glucose. This pterin may be a useful marker for certain species of cyanobacteria

Interference by plastics additives in the HPLC determination of microcystin-LR and -YR

Plastics devices used for the field collection of water samples may contain plastics additives which will interfere with the HPLC determination of the cyanobacterial toxins microcystins. The presence of the additives resorcinol monobenzoate or 2,4-dihydroxybenzophenone can interfere with the determination of microcystin-LR. The presence of bisphenol A in plastics can interfere with the determination of microcystin-YR