Abstract
SummaryCyanides are highly toxic and produced by various microorganisms as defence strategy or to increase their competitiveness. As degradation is the most efficient way of detoxification, some microbes developed the capability to use cyanides as carbon and nitrogen source. However, it is not clear if this potential also helps to lower cyanide concentrations in roadside soils where deicing salt application leads to significant inputs of ferrocyanide. The question remains if biodegradation in soils can occur without previous photolysis. By conducting a microcosm experiment using soils with/without pre‐exposition to road salts spiked with 13C‐labelled ferrocyanide, we were able to confirm biodegradation and in parallel to identify bacteria using ferrocyanide as C source via DNA stable isotope probing (DNA‐SIP), TRFLP fingerprinting and pyrosequencing. Bacteria assimilating 13C were highly similar in the pre‐exposed soils, belonging mostly to Actinomycetales (Kineosporia, Mycobacterium, Micromonosporaceae). In the soil without pre‐exposition, bacteria belonging to Acidobacteria (Gp3, Gp4, Gp6), Gemmatimonadetes (Gemmatimonas) and Gammaproteobacteria (Thermomonas, Xanthomonadaceae) used ferrocyanide as C source but not the present Actinomycetales. This indicated that (i) various bacteria are able to assimilate ferrocyanide‐derived C and (ii) long‐term exposition to ferrocyanide applied with deicing salts leads to Actinomycetales outcompeting other microorganisms for the use of ferrocyanide as C source.
Highlights
SummaryCyanides are highly toxic and produced by various microorganisms as defence strategy or to increase their competitiveness
We used 13C-labelled ferrocyanide and incubated the microcosms in the dark to prevent light-mediated dissociation. By this we were able (i) to show whether biodegradation occurs and (ii) to identify microorganisms assimilating C derived from ferrocyanide complexes using DNA stable isotope probing (DNA-SIP) combined with 16S rRNA ampliconbased TRFLP fingerprinting and pyrosequencing
Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology, Microbial Biotechnology, 9, 502–513
Summary
Cyanides are highly toxic and produced by various microorganisms as defence strategy or to increase their competitiveness. Organisms growing in the presence of cyanide must have an alternative cyanide-insensitive metabolism (Ju€nemann, 1997; Berthold et al, 2000; Richardson, 2000) and/or the capacity to degrade cyanide to harmful molecules that can be used as C and N source As the latter offers an additional advantage in nutrient limited environments, the capacity for cyanide biodegradation is widespread among soil microorganisms (Dubey and Holmes, 1995) and can occur via four pathways: (i) via hydrolysis, generating either formamide or formate and ammonia, (ii) via oxidative degradation, generating CO2 and ammonia, (iii) via reduction, generating methane and ammonia and (iv) via substitution, producing thiocyanate (Raybuck, 1992). We used 13C-labelled ferrocyanide and incubated the microcosms in the dark to prevent light-mediated dissociation By this we were able (i) to show whether biodegradation occurs and (ii) to identify microorganisms assimilating C derived from ferrocyanide complexes using DNA stable isotope probing (DNA-SIP) combined with 16S rRNA ampliconbased TRFLP fingerprinting and pyrosequencing. Detailed differences in microbial community composition and 13C assimilation among the soils are discussed
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