The susceptibility of cytochrome oxidases to cyanide means that cyanide is toxic to living cells and cyanide pollution causes great damage to microbial and other ecosystems. Cyanide pollution comes from both industrial wastes and a number of plants, many of agricultural importance, which are cyanogenic and release cyanide into the soil. Despite some understanding of the pathway of cyanide assimilation by aerobic microorganisms, there is little known about cyanide assimilation by anaerobic microorganisms. The author discusses cyanide production, utilization, degradation, and resistance by microorganisms. He concludes that among the most primitive organisms were some that could metabolize cyanide, perhaps in conjunction with other carbon and nitrogen sources. 199 references, 4 figures, 2 tables.

Microorganisms and cyanide.

Chapter 2 – Cyanide and Cyanogenic Glycosides

The widely held assumption that very few arthropods feed on ferns was questioned following field observations of arthropod damage on ferns in the state of Veracruz, Mexico. The extent and type of damage was recorded and it was found that in a measured locality, ferns were no less attacked than the angiospermous flora. As chemistry and arthropod host relationships have been shown to be so closely intertwined, plants collected in the field were analysed for both condensed tannins and cyanogenic glycosides, compounds known to be effective deterrents in temperate climates. Although all ferns tested contained tannins these did not appear to inhibit predation. Cyanogenic glycosides were present in only 3% of the fern species analysed, and it is, therefore, unlikely that they play a significant role as defensive compounds in the ferns examined.

https://sciweb.nybg.org/science2/pdfs/mb/ferns.oecologia.1978.pdf

Biochemical and evolutionary aspects of arthropod predation on ferns.

Cyanogenic glycosides are secondary plant compounds that occur widely in the plant kingdom. They are the source of HCN which can render the plant toxic if it is taken as food. The enzymes responsible for production of the HCN have long been known. More recent biosynthetic studies have established certain protein amino acids as precursors of the aglycones, and indicate N-hydroxyamino acids, aldoximes, nitriles and α-hydroxynitriles as intermediates. In sorghum the several biosynthetic enzymes catalyzing the flow of carbon atoms from l-tyrosine through such nitrogenous intermediates are located in a membrane fraction and may be capable of metabolic channeling.

Biosynthesis of cyanogenic glycosides

Plant resistance to pathogens based on preformed inhibitory substances is easy to conceive, but despite extensive studies, reviewed by Walker and Stahmann (1955), Allen (1959), Farkas and Kiraly (1962), Tomiyama (1963), Rohringer and Samborski (1967) and Wood (1967) there are only a few well-documented examples. Preformed resistance is often based on inadequate evidence; mainly the demonstration that a crude extract of a plant resistant to a pathogen contains material which reduces the growth of the pathogen in vitro. Therefore, we would like to stress some of the points which Wood (1967) considers as additional evidence required before resistance can reasonably be attributed to a particular substance.

Preformed Substances as Potential Protectants

The cyanogenic glycosides, here defined as glycosidic derivatives of α-hydroxynitriles, represent a rather limited class of natural products, which are widely distributed in the plant kingdom and, to a small extent, even in animals. A characteristic feature of these glycosides is their ability to release hydrocyanic acid on treatment with dilute acids or appropriate enzymes. The term “cyanogenic” is used to designate this property, regardless of whether pure substances, plants, or animals, are serving as the source. In the latter cases the term “cyanophoric” is occasionally employed synonymously.

R. Eyjólfsson

Papers

Recent Advances in the Chemistry of Cyanogenic Glycosides