Pyrosequencing Revealed SAR116 Clade as Dominant dddP-Containing Bacteria in Oligotrophic NW Pacific Ocean

Dong Han Choi,Dongseon Kim,Jung-Hyun Lee,Kitack Lee,Jang-Cheon Cho,Dongchull Jeon,Sung Min An,Ki-Tae Park,Jae Hoon Noh,Yiguo Hong

doi:10.1371/journal.pone.0116271

Abstract

Dimethyl sulfide (DMS) is a climatically active gas released into the atmosphere from oceans. It is produced mainly by bacterial enzymatic cleavage of dimethylsulfoniopropionate (DMSP), and six DMSP lyases have been identified to date. To determine the biogeographical distribution of bacteria relevant to DMS production, we investigated the diversity of dddP—the most abundant DMS-producing gene—in the northwestern Pacific Ocean using newly developed primers and the pyrosequencing method. Consistent with previous studies, the major dddP-containing bacteria in coastal areas were those belonging to the Roseobacter clade. However, genotypes closely related to the SAR116 group were found to represent a large portion of dddP-containing bacteria in the surface waters of the oligotrophic ocean. The addition of DMSP to a culture of the SAR116 strain Candidatus Puniceispirillum marinum IMCC1322 resulted in the production of DMS and upregulated expression of the dddP gene. Considering the large area of oligotrophic water and the wide distribution of the SAR116 group in oceans worldwide, we propose that these bacteria may play an important role in oceanic DMS production and biogeochemical sulfur cycles, especially via bacteria-mediated DMSP degradation.

Highlights

Dimethylsulfoniopropionate (DMSP) is produced mainly by phytoplankton and macroalgae in the ocean [1,2], and may function as an osmolyte, antioxidant, predator deterrent, and cryoprotectant [3,4,5,6,7]
The cleavage pathway is mediated via various DMSP lyases [13] and produces dimethyl sulfide (DMS) gas, which can be released from oceans and photochemically oxidized, acting as a cloud condensing nucleus [14]
Only a minor proportion (2–21%) of dissolved DMSP is cleaved into DMS [15], a great deal of attention has been paid to the cleavage pathway because of the relationship between DMS and climate change [14]

Summary

Introduction

Dimethylsulfoniopropionate (DMSP) is produced mainly by phytoplankton and macroalgae in the ocean [1,2], and may function as an osmolyte, antioxidant, predator deterrent, and cryoprotectant [3,4,5,6,7]. Among the six DMSP lyases, dddP and dddQ genes were found to be most abundant in the Global Ocean Sampling (GOS) data set, indicating that they play important roles in ocean DMS production [19].

Results

Conclusion