Detoxifying effect of yellow substance on E. coli in media containing copper

Abstract

DISSOLVED yellow organic matter (yellow substance) is ubiquitous in aquatic systems, and is thought to influence the state of ecosystems by affecting the transport and fate of minerals, primary production and, perhaps, the behaviour of aquatic organisms^1–4. Although much studied, yellow substance remains chemically and physically ill-defined. It is primarily responsible for the yellow colour of particulate-free natural waters which is generally accepted to be the result of the aqueous extract of decaying plant material. One of the primary constituents of plant material, lignin, is the precursor of a class of stable, yellow-brown, intermediate decay products called humins or humic substance⁵. Divided into two fractions, humic acid (base soluble) and fulvic acid (acid soluble), these compounds are insoluble in water and are typically analysed as extracts from soil or sediment. Yellow substance is the remaining yellow decay product and is often called soluble humin (dissolved humic acid). There are data, particularly differences in elemental composition and visible and ultraviolet light absorption, however, suggesting that yellow substance is a separate compound with cellulose as its source rather than lignin⁶.