Activity of the Natural Algicide, Cyanobacterin, on Angiosperms

Abstract

Cyanobacterin is a secondary metabolite produced by the cyanobacterium (blue-green alga) Scytonema hofmanni. The compound had previously been isolated and chemically characterized. It was shown to inhibit the growth of algae at a concentration of approximately 5 micromolar. Cyanobacterin also inhibited the growth of angiosperms, including the aquatic, Lemna, and terrestrial species such as corn and peas. In isolated pea chloroplasts, cyanobacterin inhibited the Hill reaction when p-benzoquinone, K3Fe(CN)6, dichlorophenolindophenol, or silicomolybdate were used as electron acceptors. The concentration needed to inhibit the Hill reaction in photosystem II was generally lower than the concentration of the known photosystem II inhibitor 343,4-dichlorophenyl)-1,1-dimethyl urea. Cyanobacterin had no effect on electron transport in photosystem I. The data indicate that cyanobacterin inhibits 02 evolving photosynthetic electron transport in all plants and that the most probable site of action is in photosystem II.The cyanobacterium (blue-green alga), Scytonema hofmanni (formerly UTEX2 1581, now UTEX 2349) was found to inhibit the growth of other algae in two species cultures (9). Inhibition was due to production and excretion of a secondary metabolite by S. hofmanni. The active metabolite was isolated and chemically characterized. This compound, called cyanobacterin, is a diaryl-substituted gamma lactone with a chlorine substituent on one ofthe aromatic rings (Fig. 1). Investigation ofthe mechanism of action of cyanobacterin showed that the compound inhibited photosynthetic electron transport in the unicellular cyanobacterium, Synechococcus sp. (ATCC 27146 from a projector lamp at 150 uE/m2. s. Conditions for measuring chloroplast electron transport were adapted from Izawa (6). The Hill reaction acceptors used for monitoring PSII activity were 0.25 mm DCPIP (Sigma Chemical Co.), 2.5 mm K3Fe(CN)6, and 0.5 mM p-benzoquinone (Fisher Scientific) and 0.2 mM silicomolybdic acid (Pfaltz and Bauer, Inc., Stanford, CT). PSI activity was measured by transfer of electrons from ascorbate-reduced DCPIP to 0.1 mm methyl viologen (Aldrich Chemical Co.) as terminal acceptor. Chl concentration of the chloroplasts suspensions was determined spectrophotometrically after extraction with 90% acetone (1 1). Highly purified cyanobacterin and anhydrocyanobacterin were extracted from S. hofmanni as previously described (12). DCMU was obtained from the Sigma Chemical Co., and dissolved in ethyl ether. RESULTSCyanobacterin has been shown to be toxic to most cyanobacteria at a minimum effective dose of 2 ug/ml (4.6 ,uM) (4). We initially tested the effect of cyanobacterin on the aquatic angiosperm, Lemna gibba, by adding similar amounts to the growth medium. The results shown in Figure 2 confirm that cyanobacterin does inhibit plant growth. The antibiotic stopped frond multiplication at a minimum dose of 0.5 Mg/ml (1. (Table I). Similar tests were attempted on terrestrial angiosperms. Cyanobacterin, when added to the soil, had no effect....

Polyphenolic Allelochemicals from the Aquatic Angiosperm Myriophyllum spicatumInhibit Photosystem II

“…Many benthic filamentous cyanobacteria produce specific inhibitors of PSII (see Smith and Doan, 1999), like cyanobacterin from Scytonema hofmannii or fischerellin A from Fischerella muscicola and Fischerella ambigua. The former inhibits the photosynthetic electron transport on the acceptor side of PSII (Gleason and Paulson, 1984;Gleason and Case, 1986), whereas the latter interrupts the electron transport at four different sites (Srivastava et al, 1998) and interferes additionally with membrane integrity. These allelopathically active compounds act differently from synthetic herbicides, an apparently Article, publication date, and citation information can be found at www.plantphysiol.org/cgi…”

Systematic Strategy for the Synthesis of Cyanobacterin and Its Stereoisomers. 1. Asymmetric Total Synthesis of Dechloro-cyanobacterin and Its Enantiomer

“…It has been found in a biological investigation to inhibit the Hill reaction in isolated chloroplasts and showed high toxicity toward other cyanobacteria, green algae and higher plants. 4) A further investigation suggested that the site of action of this compound was photosystem  (PS ). The minimum concentration to inhibit the electron transport in PS  was lower than that of the typical PS  inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU).…”

Metabolites from freshwater aquatic microalgae and fungi as potential natural pesticides

“…1). Scytonema genus has also shown algaecidal activity, displaying cyanobacterin (15) (Scytonema hofmanni) that inhibited the growth of algae and angiosperms at B5 lM dosis (Gleason and Case 1986). -3a-acetoxy-abieta-5,7,9,11,13-pentaene R = H 104 20-Nor-3a-acetoxy-abieta-5,7,9,11, 12-hydroxy-13-pentaene R = OH (Höckelmann et al 2009).…”

“…Cyanobacterin (15) Aromatic lactone Antimicrobial USA Mason et al (1982) Allelopathic USA Gleason and Case (1986), Pignatello et al (1983) Scytonema mirabile…”