Complete genome sequence of Polaribacter sejongensis NJDZ03 exhibiting diverse macroalgal polysaccharide-degrading activity

Biodegradation of poly(butylene adipate terephthalate) and poly(vinyl alcohol) within aquatic pathway

Understanding the environmental fate of biodegradable plastics in aquatic systems is crucial, given the alarming amount of plastic waste and microplastic particles transported through aquatic pathways. In particular, there is a need to analyze the biodegradation of commercialized biodegradable plastics upon release from wastewater treatment plants into natural aquatic systems. This study investigates the biodegradation behaviors of poly(butylene adipate terephthalate) (PBAT) and poly(vinyl alcohol) (PVA) in wastewater, freshwater, and seawater. Biodegradation of PBAT and PVA assessed through biochemical oxygen demand (BOD) experiments and microcosm tests revealed that the type of aquatic system governs the biodegradation behaviors of each plastic, with the highest biodegradation rate achieved in wastewater for both PBAT and PVA (25.6 and 32.2 % in 30 d, respectively). Plastic release pathway from wastewater into other aquatic systems simulated by sequential incubation in different microcosms suggested that PBAT exposed to wastewater and freshwater before reaching seawater was more prone to degradation than when directly exposed to seawater. On the other hand, PVA displayed comparable biodegradation rate regardless of whether it was directly exposed to seawater or had passed through other environments beforehand. Metagenome amplicon sequencing of 16S rRNA genes revealed distinct community shifts dependent on the type of plastics in changing environments along the simulated aquatic pathway. Several bacterial species putatively implicated in the biodegradation of PBAT and PVA are discussed. Our findings underscore the significant influence of pollution routes on the biodegradation of PBAT and PVA, highlighting the potential for wastewater treatment to facilitate rapid degradation compared to direct exposure to pristine aquatic environments.

Microbial communities associated with kelp detritus in temperate and subantarctic intertidal sediments

Kelp forests, among the most productive ecosystems on Earth, cover large areas of the South Atlantic coast. Sediment heterotrophic bacteria have a pivotal role in the degradation of kelp biomass, however, the response of sediment microbial communities to periodic kelp biomass inputs is mostly unknown. Here, we show that kelp biomass induced rapid changes in overlying water chemistry and shifts in sediment microbial communities, which differed in the experimental systems containing Macrocystis pyrifera (M) and Undaria pinnatifida (U) with sediments of the respective regions. We observed results compatible with the degradation of labile, high molecular weight compounds into smaller and more refractory compounds towards the end of the incubations. The capability of microbial communities to degrade alginate, the major component of kelp cell walls, significantly increased with respect to controls after kelp biomass addition (Absorbance at 235 nm 1.2 ± 0.3 and 1.0 ± 0.2 for M and U, respectively, controls <0.2, t = 4 days). Shifts in microbial community structure (based on 16S rRNA gene amplicon sequencing) were tightly related to the kelp treatment and, to a lesser extent, to the sediment provenance (Principal Coordinates Analysis, 80 % of variation explained in the first two axes). Dissolved oxygen, pH, salinity, alginolytic potential, Absorbance at 235 and 600 nm, total N, total C, and SUVA index correlated significantly with community structure. Differentially abundant populations between kelp-amended treatments and controls included members of the Flavobacteriia class (Algibacter and Polaribacter), and Gammaproteobacteria (Psychromonas and Marinomonas), among others. Metagenomes of M and U-amended sediments contained sequences from 18 of the 19 enzyme families related to alginate or fucoidan degradation. Specific taxonomic groups were associated with enzyme classes targeting different substrates, suggesting niche differentiation. This work expands our knowledge on the patterns of microbial assemblages from intertidal sediments in response to kelp biomass inputs.