Pathways and Substrate Specificity of DMSP Catabolism in Marine Bacteria of the Roseobacter Clade

Abstract

The volatiles released by Phaeobacter gallaeciensis, Oceanibulbus indolifex and Dinoroseobacter shibae have been investigated by GC-MS, and several MeSH-derived sulfur volatiles have been identified. An important sulfur source in the oceans is the algal metabolite dimethylsulfoniopropionate (DMSP). Labelled [2H6]DMSP was fed to the bacteria to investigate the production of volatiles from this compound through the lysis pathway to [2H6]dimethylsulfide or the demethylation pathway to [2H3]-3-(methylmercapto)propionic acid and lysis to [2H3]MeSH. [2H6]DMSP was efficiently converted to [2H3]MeSH by all three species. Several DMSP derivatives were synthesised and used in feeding experiments. Strong dealkylation activity was observed for the methylated ethyl methyl sulfoniopropionate and dimethylseleniopropionate, as indicated by the formation of EtSH- and MeSeH-derived volatiles, whereas no volatiles were formed from dimethyltelluriopropionate. In contrast, the dealkylation activity for diethylsulfoniopropionate was strongly reduced, resulting in only small amounts of EtSH-derived volatiles accompanied by diethyl sulfide in P. gallaeciensis and O. indolifex, while D. shibae produced the related oxidation product diethyl sulfone. The formation of diethyl sulfide and diethyl sulfone requires the lysis pathway, which is not active for [2H6]DMSP. These observations can be explained by a shifted distribution between the two competing pathways due to a blocked dealkylation of ethylated substrates.

Defence Chemistry Modulation by Light and Temperature Shifts and the Resulting Effects on Associated Epibacteria of Fucus vesiculosus

“…Attraction of heterotrophic bacteria by DMSP has been previously reported [27] and in addition to deterrence this attraction apparently also plays a significant role in the shaping of Fucus -associated bacterial communities. Attraction by fucoxanthin and proline was reflected in terms of overrepresentation among Flavobacteriaceae.…”

“…Certain marine heterotrophic bacteria are known to be attracted by DMSP [26] and some bacteria are known to metabolize DMSP quickly [27]. Likewise, various bacteria and other microorganisms have a capacity for uptake and metabolization of proline [28].…”

A dual-species co-cultivation system to study the interactions between Roseobacters and dinoflagellates

“…D. shibae harbors genes for three different DMSP degradation pathways in its genome (Table 4). Laboratory experiments with [ 2 H 6 ]DMSP and derivatives had demonstrated that this organism employs both, the lytic pathway releasing DMS and the demethylation pathway releasing methylsulfide (MeSH) (Dickschat et al, 2010). However, none of these genes displayed a significant change in expression in our dataset when light and dark samples were compared.…”

“…It has been shown to catabolize DMSP produced by Pfiesteria (Miller and Belas, 2004). Many Roseobacters harbor pathways for DMSP degradation and through the emitted metabolite DMS indirectly influence the abundance of cloud condensation nuclei in the atmosphere (Dickschat et al, 2010). TM1040 additionally is positively chemotactic toward DMSP (Miller and Belas, 2006).…”

Volatile Metabolites

“…These volatiles arise through the intermediacy of dimethylsulfonioproprionic acid (DMSP) (Figure 1) which occurs widely as an osmoprotective agent in algae and bacteria [88]. Lysis of DMSP by marine bacteria yields dimethylsulfide, while demethylation and subsequent lysis yields methanethiol [89]. …”