New insights into the structure and function of the prokaryotic communities colonizing plastic debris collected in King George Island (Antarctica): Preliminary observations from two plastic fragments.

In Antarctic regions, the composition and metabolic activity of microbial assemblages associated with plastic debris ("plastisphere") are almost unknown. A macroplastic item from land (MaL, 30 cm) and a mesoplastic from the sea (MeS, 4 mm) were collected in Maxwell Bay (King George Island, South Shetland) and analyzed by Fourier transform infrared spectroscopy in attenuated total reflectance geometry (FTIR-ATR), which confirmed a polystyrene foam and a composite high-density polyethylene composition for MaL and MeS, respectively. The structure and function of the two plastic-associated prokaryotic communities were studied by complementary 16S ribosomal RNA gene clone libraries, total bacterioplankton and culturable heterotrophic bacterial counts, enzymatic activities of the whole community and enzymatic profiles of bacterial isolates. Results showed that Gamma- and Betaproteobacteria (31% and 28%, respectively) dominated in MeS, while Beta- and Alphaproteobacteria (21% and 13%, respectively) in MaL. Sequences related to oil degrading bacteria (Alcanivorax,Marinobacter) confirmed the known anthropogenic pressure in King George Island. This investigation on plastic-associated prokaryotic structure and function represents the first attempt to characterize the ecological role of plastisphere in this Antarctic region and provides the necessary background for future research on the significance of polymer type, surface characteristics and environmental conditions in shaping the plastisphere.