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The ubiquity of plastic debris in marine environments raises the question, what impacts do plastics have on our marine microbiota? To investigate this, we applied bacterial 16S rRNA gene and fungal ITS2 region sequencing to identify changes in microbial biofilm community compositions on marine plastic, over time. We sampled biofilm on virgin linear low-density polyethylene (LLDPE), nylon-6 (PA) and glass after 2, 6 and 12 weeks of constant immersion in Te Whakaraupō-Lyttelton Harbour, Aotearoa-New Zealand. Of the prokaryotes, Proteobacteria and Bacteroidetes were predominant in all samples and Verrucomicrobiota were most abundant in mature biofilms. Microbial communities on the three substrate types were significantly distinct from those in the surrounding seawater, regardless of age, but not between attachment substrates. Bacterial communities occurring two weeks after immersion and fungal communities at six weeks were found to vary more among substrate types than at other times; however, no significant substrate-specific communities were identified overall. Taxa closely related to previously reported plastic-biodegrading species were found in very low abundance across all substrates, including on the glass slides. Our findings suggest that microorganisms do not selectively persist on the LLDPE or PA surfaces to gain significant direct metabolic benefit, instead using these plastics primarily as an attachment surface on which they form generalist biofilm communities.

Currently, ca. 30 million m 3 of Pinus radiata are harvested annually in New Zealand to produce timber, pulp and paper, with by-products such as bark and sawdust generated during processing. The most common use for sawdust is as a solid fuel for process heat. However, it is a feedstock that can be processed into platform biochemicals. Although conversion processes focusing on biochemical production from wood are scarce, they are becoming more commercially established. Here, reactive extrusion was explored as a continuous, fast method to depolymerise sawdust into soluble biochemicals with residence times of less than two minutes. This is substantially shorter than other biotechnology routes or conventional batch processing and highlights the potential for integration of reactive extrusion into biorefinery operations. While conventional wood extrusion focused on the solid fraction, this work extensively investigated the liquid biochemical profile. The effects of temperature, moisture content, screw speed, and screw design on the biochemical yield from sawdust were studied. The results indicated that kneading elements in the screw design were key to achieving good processing of the sawdust. A high moisture content of 50% (by weight) was instrumental in the isolation of biochemicals. Moreover, the screw speed had little to no effect on the biochemical composition obtained from the reactive extrusion process. Finally, a maximum of 6.5–7.5% of biochemicals were recovered from sawdust in the liquid phase when processed between 325 °C and 375 °C. The biochemical analyses of the liquor showed a high amount of acetic acid (up to 7913 mg/L) and methanol (up to 2277 mg/L). Furthermore, the furanic content increased with an increase in temperature between 275 °C and 375 °C, while an inverse trend was observed for aromatic phenols. The analyses also revealed that lignin and hemicellulose were depolymerised to produce oligomeric and monomeric breakdown products, while cellulose was untouched. This study successfully demonstrated the successful use of a twin-screw reactive extruder to continuously produce a biochemical-rich liquor from sawdust. Graphical abstract

We characterised plastisphere microbial communities in the polishing pond of a municipal wastewater treatment plant, applying prokaryotic 16S rRNA gene, eukaryotic 18S rRNA gene and fungal ITS2 region sequencing to identify changes in microbial biofilm community compositions over time. Pondwater and biofilm from linear low-density polyethylene (LLDPE), nylon-6 (PA), polyethylene terephthalate (PET), polylactic acid (PLA), oxo-degradable linear low-density polyethylene (OXO) and glass were sampled after 2, 6, 26 and 52 weeks of constant immersion. Microbial communities in ambient pondwater differed significantly from those forming biofilms on solid substrates. Biofilm age and depth in the water influenced microbial community compositions. However, no substrate-specific microbial communities were found among glass and plastic polymer types, regardless of artificial ageing. All substrates housed taxa associated with microbes previously reported to biodegrade plastics, being most abundant at two and 52 weeks for bacteria and fungi, respectively. Potential pathogens were found on all substrates, also being most abundant at two and 52 weeks for bacteria and eukaryotes, respectively. Our study highlights that the volume of plastics, more than its polymer form, may be most important when considering plastic's potential impacts on terrestrial and aquatic ecosystems, and for public health.

The lipid composition of cellular membranes is highly dynamic and undergoes continuous remodeling, affecting the biophysical properties critical to biological function. Here, we introduce an optical approach to manipulate membrane viscosity based on an exogenous synthetic fatty acid with an azobenzene photoswitch, termed FAAzo4. Cells rapidly incorporate FAAzo4 into phosphatidylcholine and phosphatidylethanolamine in a concentration- and cell type-dependent manner. This generates photoswitchable PC and PE analogs, which are predominantly located in the endoplasmic reticulum. Irradiation causes a rapid photoisomerization that decreases membrane viscosity with high spatiotemporal precision. We use the resulting “PhotoCells” to study the impact of membrane viscosity on ER-to-Golgi transport and demonstrate that this two-step process has distinct membrane viscosity requirements. Our approach provides an unprecedented way of manipulating membrane biophysical properties directly in living cells and opens novel avenues to probe the effects of viscosity in a wide variety of biological processes.

The lipid composition of cellular membranes is dynamic and undergoes remodelling affecting biophysical properties, such as membrane fluidity, which are critical to biological function. Here, we introduce an optical approach to manipulate membrane fluidity based on exogenous synthetic fatty acid with an azobenzene photoswitch, termed FAAzo4. Cells rapidly incorporate FAAzo4 into phosphatidylcholine (PC), the major phospholipid in mammalian cells, in a concentration- and cell type-dependent manner. This generates photoswitchable PC analogs (AzoPC), which are predominantly located in the endoplasmic reticulum (ER). Irradiation causes a rapid photoisomerization that increases membrane fluidity with high spatiotemporal precision. We use these PhotoCells to study the impact of membrane mechanics on protein export from the ER and demonstrate that this two-step process has distinct membrane fluidity requirements. Our approach represents an unprecedented way of manipulating membrane fluidity in cellulo and opens novel avenues to probe roles of fluidity in a wide variety of biological processes. Competing Interest Statement The authors have declared no competing interest.