The compatible solute dimethylsulphoniopropionate (DMSP) has important roles in marine environments. It is an anti-stress compound made by many single-celled plankton, some seaweeds and a few land plants that live by the shore. Furthermore, in the oceans it is a major source of carbon and sulphur for marine bacteria that break it down to products such as dimethyl sulphide, which are important in their own right and have wide-ranging effects, from altering animal behaviour to seeding cloud formation. In this Review, we describe how recent genetic and genomic work on the ways in which several different bacteria, and some fungi, catabolize DMSP has provided new and surprising insights into the mechanisms, regulation and possible evolution of DMSP catabolism in microorganisms.

Global agricultural emissions of the greenhouse gas nitrous oxide (N 2 O) have increased by around 20% over the last 100 y, but regulation of these emissions and their impact on bacterial cellular metabolism are poorly understood. Denitrifying bacteria convert nitrate in soils to inert di-nitrogen gas (N 2 ) via N 2 O and the biochemistry of this process has been studied extensively in Paracoccus denitrificans. Here we demonstrate that expression of the gene encoding the nitrous oxide reductase (NosZ), which converts N 2 O to N 2 , is regulated in response to the extracellular copper concentration. We show that elevated levels of N 2 O released as a consequence of decreased cellular NosZ activity lead to the bacterium switching from vitamin B 12 -dependent to vitamin B 12 -independent biosynthetic pathways, through the transcriptional modulation of genes controlled by vitamin B 12 riboswitches. This inhibitory effect of N 2 O can be rescued by addition of exogenous vitamin B 12 .denitrification | transcription | NosR | NosC G lobal atmospheric loading of the ozone-depleting greenhouse gas, nitrous oxide (N 2 O), is on the increase (1). Molecule for molecule, its radiative potential is ∼300-fold higher than carbon dioxide (2, 3), comprising ∼9% of global radiative forcing by greenhouse gases (4). In addition, atmospheric N 2 O is stable for ∼120 y. Approximately 70% of anthropogenic N 2 O loading arises from agriculture, mainly from the use of nitrogencontaining fertilizers by soil microbes for dissimilatory purposes. Taken together, these features make N 2 O an important target for mitigation strategies (5).N 2 O is an intermediate in the sequential reduction of nitrate (NO 3 − ) to di-nitrogen (N 2 ), via nitrite (NO 2 − ), nitric oxide (NO), and N 2 O, a process known as denitrification (6). Under certain conditions, the final step in denitrification is dispensed with and N 2 O is released into the atmosphere. One limiting factor in this process is copper (Cu) availability, the metal cofactor required by the N 2 O reductase (NosZ) that destroys N 2 O (5, 7, 8). During Cu-limitation the catalytic capacity of the Nos system may be exceeded by the rate of the preceding reactions that generate N 2 O (i.e., NO 3 − , NO 2 − , and NO reduction) and thus, N 2 O is emitted by denitrifying bacteria (7, 9, 10).Much attention has been given to the cytotoxic properties of NO as a free-radical and oxidant, but N 2 O is often described as a relatively inert intermediate of the nitrogen cycle. However, N 2 O exhibits cytotoxicity, as it is known to bind to and inactivate vitamin B 12 (B 12 ), an essential cellular cofactor in B 12 -dependent enzymes involved in methionine and DNA synthesis (11,12). B 12 also acts as a ligand for B 12 riboswitches that modulate gene expression in the absence of this cofactor (13,14). The possible impact of environmental N 2 O emissions on B 12 metabolism in microbiological communities has largely been ignored. As levels of N 2 O increase in the environment, there is a compelling argument for ...

Summary Background Microparticles (MPs), small vesicles shed from stimulated cells, permit cross-talk between cells within a particular environment. Their composition is thought to reflect their cell of origin, and differs according to whether they are produced by stimulation or by apoptosis. Whether MP properties vary according to stimulus is not yet known. Methods We studied the characteristics of MPs produced from monocytic THP-1 cells upon stimulation with lipopolysaccharide or a soluble P-selectin chimera, using proteomics, flow cytometry, western blotting, and electron microscopy. Results Utilizing a novel criterion of calcein-AM staining to define MPs, we found that MP populations were similar with respect to size, presence and organization of cytoskeleton, and expression of certain antigens. The MPs shared the same level of procoagulant activity. We found that MPs also have distinct characteristics, depending on stimuli. These include differences in phosphatidylserine expression and expression of proteins from specific subcellular locations such as the mitochondria, and of unique antigens such as leukocyte-associated immunoglobin-like-receptor (LAIR)-1, which was found only upon stimulation with the soluble P-selectin chimera. Conclusion We found that the properties of MPs depend on the stimulus that produced them. This supports the concept that monocytic MPs differentially modulate thrombosis, inflammation and immune regulation according to stimulus.