MEPS 507:31-38 (2014)  -  DOI: https://doi.org/10.3354/meps10842

ABSTRACT: The response of dimethylsulfoxide (DMSO) reduction activity (DRA) was examined in the marine diatom Thalassiosira pseudonana under nutrient limitation (nitrogen- or vitamin B₁₂-limitation). DRA was higher in nutrient-limited cultures (160 ± 42% of control for N-limited and 168 ± 52% for B₁₂-limited) than controls. The increased DRA is thought to be due to up-regulation of defense/repair enzymes as opposed to increased substrate availability. By supplying a chiral sulfoxide (methylphenylsulfoxide, MPSO), DRA could be tentatively assigned to a methionine sulfoxide reductase B (MsrB) enzyme due to a decrease in the amount of (R)-MPSO present in limited cultures versus control, in a similar fashion to other marine organisms. Cellular dimethylsulfoniopropionate (DMSP) and DMSO contents were also significantly higher under nutrient stress versus control, indicating physiological stress. This is the first time DRA and cellular DMSO concentrations have been shown to increase during stress conditions in a marine alga. Together, these results suggest a role in nutrient-stress management for DRA, and may provide a link between stress at the cellular level and the biogeochemical cycling of sulfur in the marine environment.

KEY WORDS: Sulfur · Nitrogen · Cobalamin · Dimethylsulfide · Diatom · Methionine sulfoxide reductase