Some bacteria may find plastic yummy

Plastic is an increasingly ubiquitous substratum in the marine environment. Consequently, it is critical to understand its effect on the microbiome. In a series of incubation experiments, Romera-Castillo et al. (2018) found that four widely used plastic types leach dissolved organic carbon (DOC) when exposed to seawater. This plastic-derived DOC may be used by bacteria from Adriatic surface waters, as evidenced by a positive linear relationship between leached DOC and consumed DOC. Importantly, artificial solar radiation decreased the bioavailability of plastic-derived DOC, as indicated by lower bacterial growth and protein synthesis. This is likely due to deleterious free radicals, produced during photodegradation of plastic.

These findings suggest that plastic could be a novel oceanic carbon source, which may alter food-web and carbon cycling dynamics. One shortcoming of this study is the unknown identity of bacterial clades. Moreover, the effect of insolation generally seems more important than that of plastic on bacterial activity, which was only rarely higher in irradiated plastic compared to control treatments. Perhaps plastic is only a meaningful carbon source in the deep sea and its usage by the respective microbiome should be investigated. Finally, the capacity to infer global trends from laboratory experimentation is limited. 

Romera-Castillo, C., Pinto, M., Langer, T. M., Álvarez-Salgado, X. A., & Herndl, G. J. (2018). Dissolved organic carbon leaching from plastics stimulates microbial activity in the ocean. Nature Communications, 9(1), 1430.