Actinomycetes in the Elbow River Basin, Alberta, Canada

Abstract

Actinomycetes can produce significant amounts of the earthy-muddy odour compounds geosmin and 2-methylisoborneol (MIB). These filamentous bacteria are found in both terrestrial and aquatic environments, and are particularly abundant in soil. They can enter freshwater systems via terrestrial runoff and subsequently cause taste and odour outbreaks in drinking water. Since it is well known that actinomycete growth and odour production is modified strongly by environmental factors such as moisture and nutrient levels, we hypothesized that watershed and stream characteristics should influence the potential odour impact of soil runoff on surface water. In this study, 1) the relationship between actinomycete abundance and characteristics such as stream discharge, turbidity and Escherichia coli levels was investigated, and 2) actinomycetes from contrasting terrestrial sources were examined for differences in their geosmin and MIB production. Actinomycetes and stream characteristics were sampled from the Elbow River, an important drinking water source for the City of Calgary (Alberta, Canada), and three tributary streams. Actinomycetes from forested regions and agricultural land were tested for taste and odour compound production. Actinomycete levels in streams were found to correlate closely with E. coli levels and to a lesser extent with turbidity, suggesting that actinomycetes are particularly abundant in runoff from terrestrial sources with fecal contamination. Most of the 18 actinomycete isolates tested were able to produce geosmin and/or MIB regardless of their terrestrial sources, suggesting that taste and odour outbreaks due to actinomycetes may be more influenced by differences in abundance than differences in source.

Biochemical and Ecological Control of Geosmin and 2-Methylisoborneol in Source Waters

“…Hoson and coworkers also found that the dissolved 2-MIB fraction was larger than the cell-bound fraction (32). In some cases, allochthonous soil runoff may be important (33,113). Biofilms can also be very significant sources, even in large, fast-flowing rivers.…”

“…The genus Streptomyces is widely used synonymously with odor-producing actinomycetes, but it is important to note that nonstreptomycete actinomycetes such as Nocardia are also potent producers of both geosmin and 2-MIB, while many streptomycetes are nonproducers (112). The two compounds are principal odor components of soil (9,40), and periods of high terrestrial runoff may introduce actinomycetes and/or their odorous metabolites into surface waters, causing episodic odor outbreaks in rivers, particularly in areas of intensive livestock operations (33,37,112,113).…”

“…Highly selective media are needed to identify and enumerate actinomycetes; different studies use different media, and these media vary in the biomass they will generate (18). Estimates using these traditional methods suggest that the abundance of actinomycetes in open waters is generally low, ranging from below detection to ϳ1.4 ϫ 10 6 cells ⅐ liter Ϫ1 (64,113,114). Immunofluorescence techniques have been employed extensively in medical and soil sciences to investigate these and other mixed microbial assemblages but are often limited by their nonspecific nature, and without appropriate controls, these methods can yield estimates that include many (other) bacterial taxa and which differ significantly from CFU.…”

“…Studies using FISH and FISH with catalyzed reporter deposition have demonstrated that active actinomycetes (which metabolize and/or incorporate labeled thymidine) are ubiquitous (60) and can be important components of the plankton even during periods when there is little or no odor (47,49). Authors have reported a wide range in the proportion of potentially odorous actinomycetes in different environments: between approximately 20% and 70% of isolates from river and lake samples have been found to be active (in vitro) producers of geosmin and/or 2-MIB (37,47,113,114).…”

Source-water odor during winter in the Yellow River area of China: Occurrence and diagnosis

“…Actinomycetes, which can grow in autumn and winter (Lanciotti et al, 2003), might be responsible for the production of these earthy/musty odor causing compounds. Actinomycetes might also enter freshwater systems via terrestrial runoff, and subsequently cause T/O outbreaks in drinking water (Zaitlin et al, 2003).…”