Environmental Factors Support the Formation of Specific Bacterial Assemblages on Microplastics

Abstract

While the global distribution of microplastics (MP) in the marine environment is currently being critically evaluated, the potential role of MP as a vector for distinct microbial assemblages or even pathogenic bacteria is hardly understood. To gain a deeper understanding, we investigated how different in situ conditions contribute to the composition and specificity of MP-associated bacterial communities in relation to communities on natural particles. Polystyrene (PS), polyethylene (PE), and wooden pellets were incubated for 2 weeks along an environmental gradient, ranging from marine (coastal Baltic Sea) to freshwater (waste water treatment plant, WWTP) conditions. The associated assemblages as well as the water communities were investigated applying high-throughput 16S rRNA gene sequencing. Our setup allowed for the first time to determine MP-dependent and -independent assemblage factors as subject to different environmental conditions in one system. Most importantly, plastic-specific assemblages were found to develop solely under certain conditions, such as lower nutrient concentration and higher salinity, while the bacterial genus Erythrobacter, known for the ability to utilize polycyclic aromatic hydrocarbons (PAH), was found specifically on MP across a broader section of the gradient. We discovered no enrichment of potential pathogens on PE or PS; however, the abundant colonization of MP in a WWTP by certain bacteria commonly associated with antibiotic resistance suggests MP as a possible hotspot for horizontal gene transfer. Taken together, our study clarifies that the surrounding environment prevailingly shapes the biofilm communities, but that MP-specific assemblage factors exist. These findings point to the ecological significance of specific MP-promoted bacterial populations in aquatic environments and particularly in plastic accumulation zones.

Microbial Colonization in Marine Environments: Overview of Current Knowledge and Emerging Research Topics

“…Through a multi-ocean basin biogeographical survey, Amaral-Zettler et al [77] showed that plastisphere communities developed on different polymer types in the North Pacific and North Atlantic Seas reflected primarily their biogeographic origins, and to a lesser extent the plastic type; therefore, differences in microbial communities among ocean basins were more significant than those among plastic polymers. Similar conclusions were obtained for bacterial communities colonizing plastics along an environmental gradient (from freshwater to marine), which were shaped firstly by the environmental conditions and secondarily by the plastic type [78].…”

“…Oberbeckmann et al [78], investigating microbial colonization of wood, HDPE and PS over 14 days along a gradient ranging from marine (coastal Baltic Sea) to freshwater (wastewater treatment plant) conditions, found that microbial communities did not differ significantly among the polymers.…”

Temporal covariation of epibacterial community and surface metabolome in the Mediterranean seaweed holobiont Taonia atomaria

“…Erythrobacter spp. are marine ubiquitous aerobic anoxygenic phototrophic bacteria, which have already been reported as the major taxa of biofilm communities on artificial surfaces (Briand et al, 2017;Oberbeckmann et al, 2018). As cyanobacteria failed to be identified in the surface community of T. atomaria, Erythrobacter spp.…”

The novel shapeshifting bacterial phylumSaltatorellota

“…Taken together, all isolated Saltatorellota strains apparently possess a continuous PG sacculus that might undergo intensive modulations during shapeshifting, amoeba-like locomotion or trunk-formation. All novel Saltatorellota isolates were obtained from microplastic particles incubated for two weeks either in the Baltic Sea or an inflowing river estuary with salinities of 1-1.5% as described before [47,57]. In order to exclude osmotic stress and to gain deeper insights into the natural habitat of these strains, water samples were taken along the southern and eastern coastline of the Baltic Sea.…”

“…For the isolation of E. mirabilis Pla133 T and R. mirabilis Pla163 T , microplastic and wood particles collected on 04 September 2014 were incubated for 16 days in an inflowing river estuary and at the Baltic Sea coast as previously described [57]. S. ferox Poly30 T was isolated from plastic particles collected on 08 October 2015 (incubation time two weeks) from the Baltic Sea at Heiligendamm pier, Germany.…”