Plastic is a ubiquitous pollutant in the marine environment. Here, we investigated how temporal changes in environmental factors affect the microbial communities formed on plastic (polyethylene terephthalate; PET) versus a ceramic substrate. In situ mesocosms (N = 90 replicates) were deployed at the sediment–water interface of a coastal lagoon and sampled every 4 weeks for 424 days. Sequencing data (16S rRNA) was parsed based on variation in temperature with the exposure starting in fall 2016 and remaining in situ through the next four seasons (winter, spring, summer and fall 2017). PET biofilms were distinct during the summer when salinity and temperature were highest. In particular, a significant shift in the relative abundance of Ignavibacteriales and Cytophagales was observed during the summer, but PET and ceramic communities were again indistinguishable the following fall. Water temperature, salinity and pH were significant drivers of PET biofilm diversity as well as the relative abundance of plastic-discriminant taxa. This study illustrates the temporal and successional dynamics of PET biofilms and clearly demonstrates that increased water temperature, salinity, pH and exposure length play a role in the formation of a plastic-specific microbial community, but this specificity can be lost with a change in environmental conditions.

Marine environments are sinks for many contaminants, including petroleum-based plastic waste. Bioplastics, or biodegradable plastics derived from renewable resources, are considered promising alternatives as numerous studies have demonstrated their degradation in marine environments. However, their rates of degradation vary and microbial consortia responsible for its degradation are not well characterized. Previous research by our group has shown that polyhydroxyalkanoate (PHA) stimulates sulfate reducing microorganisms (SRM), enriches sulfate reduction gene pools, and accumulates antibiotic and metal resistance genes. Here, we quantify the degradation rate of PHA pellets in marine sediment and present the long-term temporal changes in PHA-associated SRM communities over 424 days. For comparative purposes, polyethylene terephthalate (PET) and ceramic served as biofilm controls and the free-living microorganisms in the overlying water column served as a non-biofilm control. PHA experienced a 51% mass loss after 424 days and a generalized additive mixed model predicted that 100% mass loss would require 909 days. Throughout the course of the 424-day exposure, PHA was colonized by a distinct microbial community while PET and ceramic were colonized by similarly structured communities. SRM comprised a larger proportion of the overall community (25 – 40%) in PHA-associated biofilms as compared to PET and ceramic controls across all timepoints. Further, the diversity of SRM was greater within PHA biofilms than PET and ceramic biofilms. This study shows that PHA degrades relatively slowly and promotes a long-term shift in microbial community structure toward sulfate reduction, demonstrating the ability of this manufactured polymer to alter its environment via the disruption of biogeochemical cycling, indicating that PHA rises to the level of pollutant in benthic marine systems.

Aside from two samples collected nearly 50 years ago, little is known about the microbial composition of wind tidal flats in the hypersaline Laguna Madre, Texas. These mats account for ~42% of the lagoon’s area. These microbial communities were sampled at four locations that historically had mats in the Laguna Madre, including Laguna Madre Field Station (LMFS), Nighthawk Bay (NH), and two locations in Kenedy Ranch (KRN and KRS). Amplicon sequencing of 16S genes determined the presence of 51 prokaryotic phyla dominated by Bacteroidota, Chloroflexi, Cyanobacteria, Desulfobacteria, Firmicutes, Halobacteria, and Proteobacteria. The microbial community structure of NH and KR is significantly different to LMFS, in which Bacteroidota and Proteobacteria were most abundant. Twenty-three cyanobacterial taxa were identified via genomic analysis, whereas 45 cyanobacterial taxa were identified using morphological analysis, containing large filamentous forms on the surface, and smaller, motile filamentous and coccoid forms in subsurface mat layers. Sample sites were dominated by species in Oscillatoriaceae (i.e., Lyngbya) and Coleofasciculaceae (i.e., Coleofasciculus). Most cyanobacterial sequences (~35%) could not be assigned to any established taxa at the family/genus level, given the limited knowledge of hypersaline cyanobacteria. A total of 73 cyanobacterial bioactive metabolites were identified using ultra performance liquid chromatography-Orbitrap MS analysis from these commu nities. Laguna Madre seems unique compared to other sabkhas in terms of its microbiology.

Intestinal epithelia regulate barrier integrity when challenged by inflammation, oxidative stress, and microbes. Transforming growth factor-β1 (TGF-β1) is a cytokine with known beneficial effects on intestinal epithelia, including barrier enhancement, after exposure to proinflammatory cytokines and infectious agents. The aim of this study was to determine whether TGF-β1 directly protects intestinal epithelia during hypoxia-reoxygenation (HR). Intestinal epithelial monolayers (T84, Caco-2) were exposed to either hypoxia (1% O2, 1 h) or oxidative stress (hydrogen peroxide, 1 mM), followed by normoxic atmosphere for different time points in the absence and presence of varying concentrations of TGF-β1. Transepithelial electrical resistance (TER) assessed barrier function, with RNA extracted for reverse transcription polymerase chain reaction analysis of GPx-1, HIF-1, heme-oxygenase-1 (HO-1), and NOX-1. In some experiments, intestinal epithelia were exposed to enterohemorrhagic Escherichia coli (EHEC) O157:H7 during the reoxygenation period and TER recorded 7 h after the infectious challenge. Hypoxia-reoxygenation significantly decreased TER in intestinal epithelia compared with normoxic controls. Transforming growth factor-β1 pretreatment ameliorated HR-induced epithelial barrier dysfunction in T84 (at 1 - 3 h) and Caco-2 (1 h) monolayers. Transforming growth factor-β1 preserved barrier integrity for up to 16 h after challenge with hydrogen peroxide. In TGF-β1-treated epithelial monolayers, only HO-1 mRNA significantly increased after HR (P < 0.05 vs. normoxic controls). The EHEC-induced epithelial barrier dysfunction was significantly worsened by intestinal HR (P < 0.05 vs. normoxia-EHEC-infected cells), but this was not protected by TGF-β1 pretreatment. Transforming growth factor-β1 preserves loss of epithelial barrier integrity caused by the stress of HR via a mechanism that may involve the upregulation of HO-1 transcription. Targeted treatment with TGF-β could lead to novel therapies in enteric diseases characterized by HR injury.

Highly managed and built environments such as zoos and aquaria provide a rich source of standardized environmental monitoring data over periods of years to decades. A fifty percent water change in an 11.4-million-liter indoor artificial sea water system housing three species of marine mammals was conducted over a two-month period. Using 16S rRNA gene sequencing, the microbial community structure of the system water and three host sites (feces, skin, and exhaled breath “chuff”) of whales housed in the system were characterized. Diversity measures confirmed massive disruption to the water community structure as an expected result of the water change. Host site-associated communities remained remarkably stable. Improved understanding of host microbial community dynamics in response to environmental system perturbations allows for sound management decisions toward optimizing conditions for resident animals.