The abundant marine bacterium Pelagibacter simultaneously catabolizes dimethylsulfoniopropionate to the gases dimethyl sulfide and methanethiol

Abstract

Marine phytoplankton produce ~109 tons of dimethylsulfoniopropionate (DMSP) per year1,2, an estimated 10% of which is catabolized by bacteria through the DMSP cleavage pathway to the climatically active gas dimethyl sulfide (DMS)3,4. SAR11 Alphaproteobacteria (order Pelagibacterales), the most abundant chemoorganotrophic bacteria in the oceans, have been shown to assimilate DMSP into biomass, thereby supplying this cell’s unusual requirement for reduced sulfur5,6. Here we report that Pelagibacter HTCC1062 produces the gas methanethiol (MeSH) and that simultaneously a second DMSP catabolic pathway, mediated by a cupin-like DMSP lyase, DddK, shunts as much as 59% of DMSP uptake to DMS production. We propose a model in which the allocation of DMSP between these pathways is kinetically controlled to release increasing amounts of DMS as the supply of DMSP exceeds cellular sulfur demands for biosynthesis

Biological cycling of volatile organic carbon by phytoplankton and bacterioplankton

“…The implication is that acetaldehyde is a significant component of labile DOM. In the experiments described here, acetaldehyde oxidation activity was expressed in SAR11 cells without induction, in agreement with other research indicating that these cells have limited transcription regulation, particularly of genes for carbon catabolism (Giovannoni et al ; Sun et al ).…”

“…Rates of acetaldehyde incorporation and oxidation decreased after 3–8 h, which is typical of saturation. We do not know the cause of these apparent saturation kinetics for acetaldehyde, but in experiments with other substrates we have found that hours are required for intracellular concentrations to stabilize at their maxima (Sun et al ). Alternatively, it is possible that a decrease in the cells’ activities over time occurred, but this explanation seems less likely to us because many of Pelagibacter's metabolic pathways are constitutively expressed.…”

Revisiting the methionine salvage pathway and its paralogues

“…The extent of this pathway in methionine salvage – likely to have been of prime importance in the early times of life, before the dioxygen rise – is, however, expected to be moderate, as methanethiol is often exported as waste rather than recovered for anabolism. This is shown for example in the metabolism of Pelagibacter ubique (Sun et al ., ).…”

Coral Reef Emissions of Atmospheric Dimethylsulfide and the Influence on Marine Aerosols in the Southern Great Barrier Reef, Australia

“…DMSP is cleaved to DMS and acrylate by enzymes collectively termed DMSP‐lyases, present within coral zooxanthellae, marine microalgae, and coral‐associated and free‐living bacteria (Alcolombri et al, 2015; Bullock et al, 2017; Raina et al, 2009; Sun et al, 2016). DMS/P and acrylate rapidly scavenge these ROS forming DMSO, which may be further oxidized by ROS to MSA (Sunda et al, 2002).…”