We have developed a novel workflow (sdDE-FACS, s̲ingle d̲roplet D̲ouble E̲mulsion FACS) that allows robust production, screening, and sorting of single double emulsion droplets with complete nucleic acid recovery.

Microplastics, plastic particles smaller than 5 mm that vary in their chemical makeup depending on the plastic type, are emerging marine pollutants that serve as a novel matrix for microbial colonization in the ocean. The communities growing on the microplastics, also termed the "plastisphere", may ultimately determine their degradation, deposition, and utilization by the food web, but the factors that shape their composition and development, such as environment, plastic type, and exposure time, are still insufficiently understood. In controlled incubation experiments carried out in a tropical bay in Panama, we show that the composition of a microplastics' bacterial biofilm is not shaped by plastic type or time exposed the environment. On the other hand, we found that the eukaryotic plastisphere was shaped by both plastic type and exposure time and found that specifically diatom communities exhibited preference for some plastic types. AbstractMicroplastics in the ocean function as an artificial microbial reef, with diverse communities of eukaryotic and bacterial microbiota colonizing its surface. It is not well understood if these communities are specific for the type of microplastic on which they develop. Here, we carried out a 6-week long incubation experiment of six common plastic polymers in Bocas del Toro, Panama. The community composition of prokaryotes based on 16S rRNA gene sequencing data, when judged under a null model analysis, shows that neither plastic polymer type nor time exposed to the environment plays a significant role in shaping biofilm communities. However, the null model analyses of eukaryotic communities based on 18S rRNA gene sequences reveal that they can be significantly influenced by plastic polymer type and time incubated. This was confirmed by scanning electron microscopy, which allowed us to distinguish plastic-specific diatom communities by the end of the incubation period.

Microfluidic technologies have been used across diverse disciplines ( high-throughput biological measurement, fluid physics, laboratory fluid manipulation) but widespread adoption has been limited in part due to the lack of openly disseminated resources that enable non-specialist labs to make and operate their own devices. Here, we report the open-source build of a pneumatic setup capable of operating both single and multilayer (Quake-style) microfluidic devices with programmable scripting automation. This setup can operate both simple and complex devices with 48 device valve control inputs and 18 sample inputs, with modular design for easy expansion, at a fraction of the cost of similar commercial solutions. We present a detailed step-by-step guide to building the pneumatic instrumentation, as well as instructions for custom device operation using our software, Geppetto, through an easy-to-use GUI for live on-chip valve actuation and a scripting system for experiment automation. We show robust valve actuation with near real-time software feedback and demonstrate use of the setup for high-throughput biochemical measurements on-chip. This open-source setup will enable specialists and novices alike to run microfluidic devices easily in their own laboratories.

Marine picocyanobacteria are ubiquitous primary producers across the world’s oceans, and play a key role in the global carbon cycle. Recent evidence stemming from in situ investigations have shown that picocyanobacteria are able to sink out of the euphotic zone to depth, which has traditionally been associated with larger, mineral ballasted cells. The mechanisms behind the sinking of picocyanobacteria remain a point of contention, given that they are too small to sink on their own. To gain a mechanistic understanding of the potential role of picocyanobacteria in carbon export, we tested their ability to form “suspended” (5–60 μm) and “visible” (ca. > 0.1 mm) aggregates, as well as their production of transparent exopolymer particles (TEP)—which are a key component in the formation of marine aggregates. Additionally, we investigated if interactions with heterotrophic bacteria play a role in TEP production and aggregation in Prochlorococcus and Synechococcus by comparing xenic and axenic cultures. We observed TEP production and aggregation in batch cultures of axenic Synechococcus , but not in axenic Prochlorococcus . Heterotrophic bacteria enhanced TEP production as well as suspended and visible aggregate formation in Prochlorococcus , while in Synechococcus , aggregation was enhanced with no changes in TEP. Aggregation experiments using a natural plankton community dominated by picocyanobacteria resulted in aggregation only in the presence of the ballasting mineral kaolinite, and only when Synechococcus were in their highest seasonal abundance. Our results point to a different export potential between the two picocyanobacteria, which may be mediated by interactions with heterotrophic bacteria and presence of ballasting minerals. Further studies are needed to clarify the mechanistic role of bacteria in TEP production and aggregation of these picocyanobacteria.

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