Allelopathy in aquatic environments may provide a competitive advantage to angiosperms, algae, or cyanobacteria in their interaction with other primary producers. Allelopathy can influence the competition between different photoautotrophs for resources and change the succession of species, for example, in phytoplankton communities. Field evidence and laboratory studies indicate that allelopathy occurs in all aquatic habitats (marine and freshwater), and that all primary producing organisms (cyanobacteria, micro- and macroalgae as well as angiosperms) are capable of producing and releasing allelopathically active compounds. Although allelopathy also includes positive (stimulating) interactions, the majority of studies describe the inhibitory activity of allelopathically active compounds. Different mechanisms operate depending on whether allelopathy takes place in the open water (pelagic zone) or is substrate associated (benthic habitats). Allelopathical interactions are especially common in fully aquatic s...

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Allelopathy of Aquatic Autotrophs

Bioremediation of polluted temperate and cold temperature environments may require the activity of psychrotrophic bacteria, because their low temperature growth range parallels the ambient temperatures encountered in these environments. In the present study, 135 psychrotrophic microorganisms isolated from a variety of ecosystems in Canada were examined for their ability to mineralize 14C-labelled toluene, naphthalene, dodecane, hexadecane, 2-chlorobiphenyl, and pentachlorophenol. A number of the psychrotrophic strains mineralized toluene, naphthalene, dodecane, and hexadecane. None of the psychrotrophs were capable of mineralizing 2-chlorobiphenyl or pentachlorophenol. Those strains demonstrating mineralization activity were subsequently screened by the polymerase chain reaction (PCR) and Southern hybridization of PCR products for the presence of catabolic genes (alkB, ndoB, todC1, and xylE) involved in known bacterial biodegradative pathways for these compounds. Some of the psychrotrophs able to minerali...

Assessment of the biodegradation potential of psychrotrophic microorganisms.

Cyanobacteria produce a variety of bioactive metabolites that may have allelochemical functions in the natural environment, such as in the prevention of fouling by colonising organisms. Chemical compounds from cyanobacteria are also of biotechnological interest, especially for clinical applications, because of their antibiotic, algicidal, cytotoxic, immunosupressive and enzyme inhibiting activities. Cyanobacterial metabolites have the potential for use in antifouling technology, since they show antibacterial, antialgal, antifungal and antimacrofouling properties which could be expoited in the prevention of biofouling on man-made substrata in the aquatic environment. Molecules with antifouling activity represent a number of types including fatty acids, lipopeptides, amides, alkaloids, terpenoids, lactones, pyrroles and steroids. The isolation of biogenic compounds and the determination of their structure may provide leads for future development of, for example, environmentally friendly antifouling paints. An advantage of exploring the efficacy of cyanobacterial products is that the organisms can be grown in mass culture, which can be manipulated to achieve optimal production of bioactive substances. Phycotoxins and related products from cyanobacteria may serve as materials for antimicro- and antimacrofouling applications. A survey of antibiotic compounds with antifouling potential revealed more than 21 different antifouling substances from 27 strains of cyanobacteria.

Antifouling potential of cyanobacteria: a mini-review

Cyanobacteria produce a large number and variety of bioactive allelochemical substances, with a diverse range of biological activities and chemical structures, and with effects on many biochemical processes within cells. An increasing number of such metabolites is being found to be directed against oxygenic photosynthetic processes, which, in the microbial world, are unique to algae and cyanobacteria. Such chemicals are likely to be involved in regulating natural populations, and are potentially useful as biochemical tools, and as herbicidal or biocontrol agents.

Cyanobacterial metabolites with bioactivity against photosynthesis in cyanobacteria, algae and higher plants

The chemical ecology of cyanobacteria

Structure of the antibiotic cyanobacterin, a chlorine-containing γ-lactone from the freshwater cyanobacterium Scytonema hofmanni

The 2nd year of a 2-year study of the fate of pentachlorophenol in outdoor artificial streams focused on details of microbial degradation by a combination of in situ and laboratory measurements. Re...

Response of the microflora in outdoor experimental streams to pentachlorophenol: environmental factors.

Demethylation of methylcobalamin by platinum(IV) platinum(II) couples. Methyl transfer within a trinuclear intermediate

Demethylation of methylcobalamin by platinum(IV) platinum(II) couples. Formation of methylplatinum(IV) products

A number of analogs of the title compound (1), with several different functional groups in place of the 3-OH and with a variety of substituents, were tested for biological acitivity by a laboratory walking-beetle assay. The electroantennogram (EAG) response was determined for many of these, as well. Field tests with baited sticky traps were carried out on compounds with activity in the walking-beetle assay and/or that gave a high EAG response. Structure-activity correlations with parameters reflecting hydrophobic, steric, electronic, and van der Waals interactions with olfactory receptors were examined primarily on the basis of the behavioral tests. Electronic substituent effects on the 3-position functional group and steric effects were found to correlate best. It is suggested that the strength of a hydrogen bond to the 3-oxygen or 3-nitrogen (as proton acceptor) is important in chemoreception by receptors that are involved in the behavioral response.

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Joseph J. Pignatello

Papers

Structure of the antibiotic cyanobacterin, a chlorine-containing γ-lactone from the freshwater cyanobacterium Scytonema hofmanni

Response of the microflora in outdoor experimental streams to pentachlorophenol: environmental factors.

Demethylation of methylcobalamin by platinum(IV) platinum(II) couples. Methyl transfer within a trinuclear intermediate

Demethylation of methylcobalamin by platinum(IV) platinum(II) couples. Formation of methylplatinum(IV) products

Structure-activity correlations among analogs of 4-methyl-3-heptanol, a pheromone component of the european elm bark beetle (Scolytus multistriatus)