Determination of bacterial diversity and degrees ofbiodegradation on microplastic surfaces found in the barentssea

This thesis aims to identify the bacterial diversity on the surface of microplastics (MP) in the Barents Sea and to investigate the biodegradation processes of these bacteria on microplastics and polyethylene (PE) polymers in detail. Between July and August 2023, microplastics were collected from 20 stations in the Barents Sea using a manta trawl net. Optical fluorescence microscopy and stereomicroscopy were used to characterize the isolated microplastics. Morphological and molecular analyses were conducted to identify bacteria on microplastic surfaces. Both preliminary screening and biodegradation studies were performed on bacterial isolates. Synthetic fibers were identified as the most common type of microplastics in the Barents Sea. The isolated bacteria exhibited high diversity and actively contributed to biodegradation processes on microplastic surfaces. The findings led to the discovery of new species unique to the region and the preservation of bacteria with significant biodegradation capacity. The physical and chemical properties of the microplastics were characterized in detail using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The study confirmed the presence of various bacterial groups on microplastic surfaces. Preliminary results revealed that bacterial isolates degraded polyethylene and fibril-structured microplastics from the region. For PE biodegradation, 10 bacterial strains were identified: Acinetobacter radioresistens, Psychrobacter pulmonis, Staphylococcus hominis, Bacillus pacificus, Bacillus pumilus1, Kocuria polaris, Exiguobacterium alkaliphilum, Bacillus pumilus2, Micrococcus luteus, and Planococcus rifietoensis. For MP biodegradation, three strains were reported: Acinetobacter radioresistens, Staphylococcus hominis, and Bacillus pumilus.