A novel inhibitory interaction between dimethylsulfoniopropionate (DMSP) and the denitrification pathway

Abstract

Dimethylsulfoniopropionate (DMSP) is an abundant organic sulfur compound in marine algae and denitrification influences nitrogen availability to primary producers, the key regulators of coastal eutrophication. In this study, we tested the effect of DMSP on the nitrous oxide (N 2 O) reduction step of denitrification in sediments and biofilms from the Douro and Ave estuaries (NW Portugal) and in pure cultures of a denitrifying bacterium, Ruegeria pomeroyi. N 2 O accumulation rates were monitored in sediment slurries and bacterial cell suspensions amended with DMSP concentrations ranging from 0 to 5 mM. In these treatments N 2 O accumulation rates increased linearly with DMSP concentration (R 2 from 0.89 to 0.99, p \ 0.001), suggesting an inhibitory effect of DMSP on the nitrous oxide reductase activity. The addition of DMSP to sediments and bacterial culture resulted in accumulation of dimethylsulfide (DMS) as well as N 2 O. However, no direct inhibition on N 2 O reductase activity by DMS was observed. Natural concentrations of DMSP in the different estuarine sites were found to be linearly correlated to natural N 2 O effluxes (R 2 = 0.64, p \ 0.001), suggesting that DMSP may negatively affect N 2 O reductase in situ. This newly identified interaction between DMSP and N 2 O emissions may have a significant ecological role as the inhibition of the nitrous oxide reduction enhances nitrogen loss via N 2 O. Since N 2 O is a powerful greenhouse gas, the results from Electronic supplementary material The online version of this article (

Incongruous variation of denitrifying bacterial communities as soil N level rises in Canadian canola fields

“…We found low nirK gene abundance when Cu concentration was below 0.9 mg g À1 , suggesting that soil Cu deficiency may limit denitrification. This threshold is lower than previously reported in prairie soils (Magalhães et al, 2012).…”

Methanethiol accumulation exacerbates release of N2O during denitrification in estuarine sediments and bacterial cultures

“…3A). In a recent study (Magalhães et al ., 2010) it was demonstrated that progressive additions of DMSP inhibited the reduction of nitrous oxide (N 2 O) to atmospheric nitrogen (N 2 ), and this was found to occur in several estuarine sediments and rocky biofilms as well as in R. pomeroyi cell suspensions. DMSP is known to yield MeSH from the demethylation/demethiolation pathway (Kiene, 1996; Kiene et al ., 1999; 2000).…”

“…We have recently demonstrated that the organic sulfur compound dimethylsulfoniopropionate (DMSP) may also cause inhibition of the terminal step of denitrification (Magalhães et al ., 2010). However, in this study it was not possible to discriminate whether it was DMSP per se , or some compound(s) known to accumulate during its catabolism, that was responsible for the inhibitory activity (Magalhães et al ., 2010).…”

“…We have recently demonstrated that the organic sulfur compound dimethylsulfoniopropionate (DMSP) may also cause inhibition of the terminal step of denitrification (Magalhães et al ., 2010). However, in this study it was not possible to discriminate whether it was DMSP per se , or some compound(s) known to accumulate during its catabolism, that was responsible for the inhibitory activity (Magalhães et al ., 2010). Degradation of DMSP by bacteria is one of the primary routes for formation of the volatile reduced organic sulfur compounds dimethylsulfide (DMS) and methanethiol (MeSH) (Kiene, 1996; Kiene et al ., 2000).…”

“…This study was motivated by the results obtained in our recent research in which we demonstrated that DMSP and/or its degradation products interfere with the nitrous oxide reductase step of denitrification (Magalhães et al ., 2010). In that report, we demonstrated that DMS was not the inhibitory compound.…”