evidence of widespread and diverse groups of methylotrophs in the ocean that have potential to significantly impact marine and estuarine ecosystems. One-carbon compounds used as a carbon and energy source by methylotrophs are found throughout the ocean. These compounds include methane, methanol, methylated amines, methyl halides, and methylated sulfur compounds, such as dimethylsulfide (DMS) and dimethylsulfoxide (DMSO). Some of these compounds are produced by phytoplankton and some come from the atmosphere. Studies incorporating a wider range of one-carbon substrates have found increasing diversity of methylotrophs, suggesting that the diversity of this bacterial group has not yet fully been explored. Because these compounds are volatile and impact the climate and atmosphere, research on the interaction of these bacteria with these one-carbon compounds can also help understanding of air-sea fluxes of these compounds, which impact climate predictions. For example, it is uncertain whether the ocean acts as a net source or sink of atmospheric methanol, but a diverse set of methylotrophs use methanol as their main energy source. In some regions, methylotrophs have been found to be a net sink of methanol, while in others a product of methylotroph activity, methylamine, has been found to be emitted from the ocean and form aerosols. The net direction of these fluxes depends on the utilization by methylotrophs. Studies have found that methylotrophic capacity varies with the productivity of a system, so the impacts of methylotrophy are likely seasonal. Because some of the one-carbon compounds used by methylotrophs, such as methanol and TMAO, are produced by phytoplankton, their availability will vary temporally and seasonally depending on phytoplankton blooms, weather events, and other ecosystem inputs. This means that methylotrophic metabolism is expected to follow similar dynamics, which will then impact biogeochemical cycles and carbon fluxes. Impacts of methylotrophs were also found in deep-sea hydrothermal vents. Methylotrophs, along with sulfur oxidizers and iron oxidizers, expressed key proteins associated with carbon fixation. These types of studies will contribute to further understanding of deep sea carbon cycling and the connectivity between deep ocean and surface carbon cycling. The expansion of omics technologies has accelerated research on the diversity of methylotrophs, their abundance and activity in a variety of environmental niches, and their interspecies interactions. Further research must be done on these bacteria and the overall effect of bacterial drawdown and transformation of one-carbon compounds in the ocean. Current evidence points to a potentially substantial role for methylotrophs in the