Intracellular Dimethylsulfoxide (Dmso) in Unicellular Marine Algae: Speculations on Its Origin and Possible Biological Role

Abstract

Recent studies have established that aqueous phase concentrations of dimethylsulfoxide (DMSO) often exceed those of dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS). Yet, in comparison to DMSP and DMS, DMSO remains a poorly understood component of the marine sulfur cycle. Much of what is known about the mechanisms for the formation and loss for DMSO is inferred from laboratory experiments, and no explanation exists to rationalize how a large pool of DMSO is maintained. One formation pathway that, until very recently, has been ignored involves the direct synthesis of DMSO by marine phytoplankton. This review examines some of the circumstantial evidence for DMSO in marine particulate material and recent reports containing preliminary data for particulate DMSO (DMSOp) in the marine environment. Drawing on literature from a range of scientific disciplines, speculations on the possible origins and biological functions of intracellular DMSO are also made. On the basis of its physicochemical properties, intracellular DMSO could have a potential role as a cryoprotectant, a specialist cryo‐osmoregulator in extreme environments, an intracellular electrolyte modifier, and a free‐radical scavenger. The review also assesses the impact of DMSOp at both the organism and the global level. Consideration is given to the marine biogeochemical cycling of sulfur and potential links to climate control.

Extracellular respiration of dimethyl sulfoxide by Shewanella oneidensis strain MR-1

“…DMS production is a significant environmental concern because DMS is an antigreenhouse gas, directly impacting cloud formation and potentially influencing global climate (15). DMSO is predominant in aquatic systems in both soluble and particulate (algaeassociated) phases (4,7,9,10). Anaerobic respiration of DMSO by bacteria could be an important input into the marine DMS budget in oxic waters, given that anoxic microenvironments exist in marine snow aggregates (40,41).…”

“…Although not directly testing the hypothesis that extracellular respiration of DMSO allows S. oneidensis to respire this compound at low temperatures, it does demonstrate the capacity of the organism to grow under these conditions. Given the prevalence of DMSO in marine ecosystems (4,6), and that most of the marine environment exists at low temperatures, the ability of S. oneidensis to respire DMSO extracellularly may confer a selective advantage for growth in cold anoxic microenvironments, for reasons that will be discussed below.…”

“…systems (4,7). Accessing this source of DMSO for respiration might be difficult using traditional mechanisms.…”

Environmental constraints on the production and removal of the climatically active gas dimethylsulphide (DMS) and implications for ecosystem modelling

“…In addition to DMSO being ubiquitous in seawater in the dissolved (or filterable DMSO d ) phase, evidence is also gathering for the direct production of particulate DMSO (GF/F retained DMSO p ) by cultures and natural assemblages of marine microalgae. DMSO has been the subject of three reviews (Hatton et al 2004;Lee and de Mora 1999a;Lee and de Mora 1999b) and whilst we aim not to be overly repetitive here, it is nonetheless important to underline some pertinent information regarding particulate DMSO. This compound is remarkable in its ability to permeate intact biological membranes and it is well known as an effective radical scavenger.…”

Elevated levels of dimethylated‐sulfur compounds in Lake Bonney, a poorly ventilated Antarctic lake

“…The biogeochemical cycle of these compounds in seawater is complex. Both DMSP and DMSO are present in phytoplankton (Vairavamurthy et al 1985;Simó et al 1998a), but production of each compound appears to be strongly species dependent (Keller et al 1989;Lee et al 2001). Release of intracellular DMSP and conversion to DMS occurs through a number of processes including grazing, viral infections, the lysis of senescent cells, and enzymatic cleavage (see reviews by Malin et al 1992;Liss et al 1997;Simó 2001).…”