The gastrointestinal tract is a critical interface for microplastic and nanoplastic exposure, yet causal links to health outcomes remain uncertain. We outline current methodological challenges and provide a list of minimum standards for rigorous study design, standardized reporting and careful attention to interpretations to distinguish mechanism from signals.

Soil-borne pathogens can influence microbial communities and ecosystem function, making it important to understand their broader ecological impacts. We investigated interactions between Phytophthora agathidicida (the causal agent of kauri tree dieback) and soil microbial communities, while also comparing detection and community-profiling methods. Soils from 60 kauri trees across three sites in the Waitākere Ranges, New Zealand, were analysed using loop-mediated isothermal amplification (LAMP) for pathogen detection, and 16S rRNA gene/ITS gene amplicon sequencing alongside shotgun metagenomics for community characterisation. LAMP detected P. agathidicida in 39/60 samples, while shotgun sequencing detected Phytophthora-associated DNA at low abundance across all samples. Microbial community structure and functional potential showed weak association with pathogen presence, though differential abundance testing identified several genera enriched in pathogen-detected soils, including taxa previously linked to disease suppression. Amplicon and shotgun profiles indicated broadly comparable patterns at higher taxonomic and functional levels, while differences between approaches emerged primarily at finer taxonomic resolution. Importantly, functional predictions from PICRUSt2 closely matched shotgun-derived profiles at broader scales, indicating its suitability as a cost-effective tool for broad-scale monitoring. These findings suggest limited direct pathogen effects on microbial communities and highlight how integrating molecular approaches provides complementary insights into soil microbiome-pathogen interactions.

Dynamic oxygen fluctuations in activated sludge were investigated to enhance valuable biochemical production during wastewater treatment. Batch experiments compared constant aeration with rapid cycling between oxygen-rich and oxygen-poor states. Fluctuating oxygen concentrations (0-2 mg/L) significantly increased production of valuable biochemicals compared to constant oxygen concentration (2 mg/L). Continuous oxygen perturbations increased free amino acids by 35.7 f 7.6 % and free fatty acids by 76.4 f 13.0 %, while intermittent perturbations with anoxic periods enhanced free amino acids by 42.4 f 8.1 % and free fatty acids by 39.3 f 7.7 %. Fourteen standard amino acids showed significant increases, and most fatty acids had carbon chain lengths between C12-C22. Mechanistically, oxygen perturbations activated FNR and ArcA regulons, resulting in lower relative abundances of TCA cycle enzymes and higher abundances of amino acid and fatty acid biosynthetic enzymes. These findings demonstrate that controlled oxygen fluctuations in wastewater treatment can enhance the biochemical value of activated sludge with minimal process modifications, facilitating resource recovery.

The gut microbiota is a dynamic component of insects’ physiology and development, yet how these microbes interact with their hosts remains poorly understood. We examined how diet impacts the gut microbiota and metabolome of Spodoptera litura fed three different diets under laboratory conditions (i.e., Chinese cabbage, tobacco and an artificial diet). Our results revealed significant dietary influences on microbial community structure and metabolite abundance. We also identified the prevalence of microbe–metabolome interactions across populations with distinct metabolite variations. Notably, dietary-driven patterns in these interactions were observed, including a complete turnover of microbial taxa contributing to metabolites related to vitamin B metabolism (such as nicotinate) when comparing natural plant-fed hosts to those fed artificial diets, despite the identical overall contributions of all taxa to this metabolism between dietary groups. Furthermore, most microbe–host interactions observed in individuals fed artificial diets were predominantly related to metabolites associated with amino acid metabolisms, such as L-methionine, L-citrulline and urea, likely due to the high quantity and variety of proteins contained in their diets. These results underscore the previously overlooked impacts of artificial diets, affecting not only gut microbial communities or host metabolomes independently, but also microbe–insect interactions. Our study highlights the importance of investigating microbial functions and their metabolic interactions with hosts instead of focusing solely on descriptive taxonomic research. Additionally, our findings emphasise that a thorough assessment of the often-overlooked effect of laboratory-rearing technologies using artificial diets is important when designing future experiments or drawing conclusions about real-world scenarios based on in-house experiments.

AimPlant growth-promoting bacteria (PGPB) play crucial roles in supporting plant growth and, therefore, in undisturbed ecosystems and agricultural systems. We aimed to understand how these microbial communities change under different land use and environmental conditions. This is an important prerequisite to utilising the positive impact PGPB may have for sustainable food production.Location537 sites across Aotearoa New Zealand.Time Period2013-2018.Major Taxa StudiedPlant growth-promoting bacteria (PGPB).MethodsWe surveyed the PGPB in indigenous and exotic plantation forests, sheep and beef grasslands, dairy pastures and horticulture sites.ResultsPGPB community alpha-diversity increased with land use intensity, and the greatest portion of explainable variation in alpha-diversity was accounted for by soil nutrients, metal concentrations, and unexplained spatial patterns. Variation in PGPB community composition, on the other hand, was highest in the forest and horticulture sites and lowest in the grazed pastures. The variation was best accounted for by shared variation among land use, soil nutrients and soil metal concentrations. The relative abundance of nitrogen-fixing PGPB taxa decreased with land use intensity, largely driven by a decrease in Rhizobiales. In contrast, taxa in the order Bacillales, known for phosphate and potassium solubilisation, increased in relative abundance. Key environmental variables limiting the distributions of specific PGPB taxa included soil pH, several nutrients and the concentrations of cadmium and zinc.Main ConclusionsOverall, we showed that PGPB show distinct patterns in response to land use and soil environmental variables, and these results contribute towards an understanding of the interplay between how we use our soil, their physicochemical properties and the function of the microbial communities within them. This increased understanding of the distribution of PGPB is crucial for advancing our ability to optimise and take advantage of the benefits these bacteria bring to both natural and agricultural land.

Plastics in the worlds oceans are exposed to diverse environmental stressors that fragment them, accelerating the leaching of associated additives. The impact of potentially toxic plastic degradation products and additives on marine microorganisms remains poorly understood. We assessed the impact of plastic leachate on marine microbial communities in vitro by exposure to one of four plastic leachates (from linear low-density polyethylene [LLPDE], polyamide-6 [or polycaprolactam; PA6], polyethylene terephthalate [PET] and polylactic acid [PLA]), prepared by immersing plastics in artificial seawater salts broth for three months at 80 C. Microbial communities were then exposed to different leachates, noting that lower concentrations of plastic additives leached from the more inert plastic types (LLDPE and PET), as determined by GC-MS. PLA-leachate exposed communities differed significantly in composition from other plastic-leachate-exposed communities (PERMANOVA, P=0.001) as assessed by 16S rRNA gene and ITS region amplicon sequencing. Communities exposed to PLA-leachate contained a higher proportion of Proteobacteria, specifically Halomonas spp., previously reported to degrade LDPE and common plasticisers. Greater relative abundances of Psathyrellaceae fungi also distinguished these communities from those exposed to other plastic leachates. However, despite significant differences in the structure of communities exposed to PLA-leachate, we found no difference in the relative abundances of gene transcripts associated with plastic degradation. While biodegradable plastics such as PLA may persist for shorter times in the environment than more inert plastics, our study indicates greater consequences for marine microbial communities. ### Competing Interest Statement The authors have declared no competing interest.

Oceanic plastic pollution provides surfaces for microbial biofilm development, which may potentiate ecosystem dysbiosis by releasing toxins, providing carbon for microbial growth, and transporting pathogens and invasive species. This study investigated how plastic type, physico-chemical characteristics, ultraviolet-ageing, water temperature, depth and submersion duration (up to twelve weeks) influence marine plastisphere communities across Aotearoa New Zealand. Initial colonisation was dominated by diatoms, with network analyses identifying keystone diatom taxa such as Bacillariaceae during the first week, followed by bacterial taxa such as Sulfurovum by week two. Early-stage community composition differed between seawater and hard surfaces (plastic and glass), and between plastics. Bacterial alpha-diversity was reduced on more hydrophobic plastics, while beta-diversity was influenced by manganese and zinc content (for bacteria), and crystallinity (for diatoms and bacteria). Random Block-Forest modelling revealed distinct microbial associations with polyamide and polyolefins (LLDPE and oxo-LLDPE), whereas PET exhibited lower taxonomic specificity and was frequently misclassified as PLA, its fellow polyester. Considering risk species, the pathogen Balamuthia was present on plastics but not from seawater, and the non-indigenous tunicates Ciona savigny and Ascidiella aspersa, and plant pathogen Puccinia graminis, were important plastic-specific indicator species. Our findings contribute to a holistic understanding of how plastic physico-chemical properties shape marine plastisphere dynamics and succession. They also highlight how plastics act as selective substrates for harmful and invasive species, posing risks to biodiversity, ecosystems, and marine industries.

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.

Microbial degradation can provide an avenue for the remediation of plastic pollution, contributing to the urgent environmental problem of global plastic waste. We demonstrate the degradation of polycaprolactone (PCL) by Clonostachys rosea and elucidate its underlying molecular mechanisms. We constructed the genome of this fungal strain and monitored changes in gene expression when exposed to PCL. Twelve genes linked to PCL degradation were found in the genome of C. rosea, and some of them were upregulated in the presence of the plastic, including genes coding for two cutinases. We heterologously expressed the enzymes coded by both genes and confirmed their activity against PCL polymers. We also demonstrate that one of the enzymes was active against polyethylene terephthalate polymers. Glucose inhibited the expression of both genes, completely halting the plastic biodegradation process, possibly serving as a preferred and readily metabolizable carbon source compared with PCL. We confirm the presence of key metabolic pathways linked to PCL degradation in C. rosea, including fatty acid degradation, providing further evidence of the mechanisms central to plastic biodegradation.IMPORTANCEPlastic pollution is one of our most pressing environmental challenges, with billions of tons of plastic waste accumulating in our ecosystems. While recycling helps, it cannot fully address this crisis, making it crucial to find new solutions. Our study reveals how a common soil fungus, Clonostachys rosea, can break down certain plastics, specifically polycaprolactone and polyethylene terephthalate. We identified the exact genes and enzymes responsible for this ability and showed how different environmental conditions affect the fungus's plastic-degrading capabilities. Notably, we discovered that adding glucose completely stops the fungus from breaking down plastic, suggesting that careful control of growth conditions is essential for effective plastic degradation. These findings are significant because they provide a detailed blueprint for optimizing plastic biodegradation using fungi, potentially leading to more effective ways to tackle plastic pollution. This research represents a crucial step toward developing practical, environmentally friendly solutions for plastic waste management.

Plastics in the world's oceans are exposed to diverse environmental stressors that accelerate fragmentation and the leaching of associated additives. The impact of potentially toxic plastic degradation products and additives on marine microorganisms remains poorly understood. We assessed the impact of plastic leachate on marine microbial communities in vitro by exposure to one of four plastic leachates [from linear low-density polyethylene (LLPDE), polyamide-6 (or polycaprolactam; PA6), polyethylene terephthalate (PET), and polylactic acid (PLA)], prepared by immersing plastics in artificial seawater salts broth for three months at 80°C. Microbial communities were then exposed to different leachates. PLA-leachate-exposed communities differed significantly in composition from other plastic-leachate-exposed communities (PERMANOVA, P=0.001) as assessed by 16S rRNA gene and ITS region amplicon sequencing. Communities exposed to PLA leachate contained a higher proportion of Proteobacteria, specifically Halomonas spp. Greater relative abundances of Psathyrellaceae fungi also distinguished PLA-leachate communities. Despite significant differences in the structure of communities exposed to PLA leachate, we found no difference in the relative abundances of differentially expressed gene transcripts associated with known plastic degradation genes. While biodegradable plastics persist for shorter times in the environment than traditional plastics, our study indicates the potential for these plastic types to impact marine microbial communities.

Abstract Background Stream ecosystems comprise complex interactions among biological communities and their physicochemical surroundings, contributing to their overall ecological health. Despite this, many monitoring programs ignore changes in the bacterial communities that are the base of food webs in streams, often focusing on stream physicochemical assessments or macroinvertebrate community diversity instead. We used 16S rRNA gene sequencing to assess bacterial community compositions within 600 New Zealand stream biofilm samples from 204 sites within a 6-week period (February–March 2010). Sites were either dominated by indigenous forests, exotic plantation forests, horticulture, or pastoral grasslands in the upstream catchment. We sought to predict each site’s catchment land use and environmental conditions based on the composition of the stream bacterial communities. Results Random forest modelling allowed us to use bacterial community composition to predict upstream catchment land use with 65% accuracy; urban sites were correctly assigned 90% of the time. Despite the variation inherent when sampling across a ~ 1000-km distance, bacterial community data could correctly differentiate undisturbed sites, grouped by their dominant environmental properties, with 75% accuracy. The positive correlations between actual values and those predicted by the models built using the stream biofilm bacterial data ranged from weak (average log N concentration in the stream water, R2 = 0.02) to strong (annual mean air temperature, R2 = 0.69). Conclusions Freshwater bacterial community data provide useful insights into land use impacts on stream ecosystems; they may be used as an additional measure to screen stream catchment attributes.

Globally, there is a move towards using local, native species for ecotoxicological risk assessments. Anthropogenic stressors from urban, agricultural, and industrial activities can impact the health of receiving ecosystems. Biomarkers can provide valuable insights as early warning signals of the potential environmental impacts of stressors. The aim of this study was to develop biomarkers in the green-lipped mussel (Perna canaliculus), a potential bioindicator of environmental health for coastal marine ecosystems in New Zealand. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) assays targeting the expression of genes involved in oxidative stress, xenobiotic transfer, membrane transportation, cellular and DNA response/repair, and endocrine disruption were developed and validated for P. canaliculus. We found significant modulation of genes associated with oxidative stress, xenobiotic transfer, membrane transport, endocrine disruption, and genotoxicity in P. canaliculus following 48-hour exposures to copper and benzo[α]pyrene. These results demonstrate the potential of P. canaliculus as a bioindicator species for environmental risk assessment. The gene expression assays showed potential as early indicators of exposure to the chemicals tested but require additional validation to assess their ability to predict effects at higher levels of biological organisation.

Plastic pollution causes detrimental environmental impacts, which are increasingly attributed to chemical additives. However, the behaviour of plastic additives in the marine environment is poorly understood. We used a marine deployment experiment to examine the impact of weathering on the extractables profile, analysed by liquid chromatography-mass spectrometry, of four plastics at two locations over nine months in Aotearoa/New Zealand. The concentration of additives in polyethylene and oxo-degradable polyethylene were strongly influenced by artificial weathering, with deployment location and time less influential. By comparison, polyamide 6 and polyethylene terephthalate were comparatively inert with minimal change in response to artificial weathering or deployment time. Non-target analysis revealed extensive differentiation between non-aged and aged polyethylene after deployment, concordant with the targeted analysis. These observations highlight the need to consider the impact of leaching and weathering on plastic composition when quantifying the potential impact and risk of plastic pollution within receiving environments.

Wastewater treatment facilities can filter out some plastics before they reach the open environment, yet microplastics often persist throughout these systems. As they age, microplastics in wastewater may both leach and sorb pollutants and fragment to provide an increased surface area for bacterial attachment and conjugation, possibly impacting antimicrobial resistance (AMR) traits. Despite this, little is known about the effects of persistent plastic pollution on microbial functioning. To address this knowledge gap, we deployed five different artificially weathered plastic types and a glass control into the final maturation pond of a municipal wastewater treatment plant in Ōtautahi-Christchurch, Aotearoa/New Zealand. We sampled the plastic-associated biofilms (plastisphere) at 2, 6, 26, and 52 weeks, along with the ambient pond water, at three different depths (20, 40, and 60 cm from the pond water surface). We investigated the changes in plastisphere microbial diversity and functional potential through metagenomic sequencing. Bacterial 16S ribosomal RNA genes composition did not vary among plastic types and glass controls (P = 0.997) but varied among sampling times [permutational multivariate analysis of variance (PERMANOVA), P = 0.001] and depths (PERMANOVA, P = 0.011). Overall, there was no polymer-substrate specificity evident in the total composition of genes (PERMANOVA, P = 0.67), but sampling time (PERMANOVA, P = 0.002) and depth were significant factors (PERMANOVA, P = 0.001). The plastisphere housed diverse AMR gene families, potentially influenced by biofilm-meditated conjugation. The plastisphere also harbored an increased abundance of genes associated with the biodegradation of nylon, or nylon-associated substances, including nylon oligomer-degrading enzymes and hydrolases.IMPORTANCEPlastic pollution is pervasive and ubiquitous. Occurrences of plastics causing entanglement or ingestion, the leaching of toxic additives and persistent organic pollutants from environmental plastics, and their consequences for marine macrofauna are widely reported. However, little is known about the effects of persistent plastic pollution on microbial functioning. Shotgun metagenomics sequencing provides us with the necessary tools to examine broad-scale community functioning to further investigate how plastics influence microbial communities. This study provides insight into the functional consequence of continued exposure to waste plastic by comparing the prokaryotic functional potential of biofilms on five types of plastic [linear low-density polyethylene (LLDPE), nylon-6, polyethylene terephthalate, polylactic acid, and oxygen-degradable LLDPE], glass, and ambient pond water over 12 months and at different depths (20, 40, and 60 cm) within a tertiary maturation pond of a municipal wastewater treatment plant.

In this study, we examine public perceptions of the importance of addressing marine ecosystem problems by including an item (which we treated as a dependent variable) in the Environment IV module of the International Social Survey Programme (ISSP) in New Zealand. Overall importance perception was high (mean rating of 4.44 on a 5-point scale). However, our hypotheses that ratings on ISSP items, which implicitly represent marine stressors (e.g., air pollution, nuclear waste), would be consistently associated with high-importance ratings for addressing marine ecosystem problems were not supported. This observation suggests that perceptions of marine issues are not necessarily underpinned by an understanding of multiple marine stressors. Including compulsory marine-related items in the ISSP could provide a clearer understanding of public perceptions of marine ecosystems and assist in informing public education and communication. This inclusion would offer a valuable global perspective, given that the ISSP is implemented in Western and non-Western countries. The ISSP offers questions on multiple environmental domains, including attitudinal, behavioral, and political and unique demographic questions that would enable in-depth country-comparative analyses of marine-related perceptions not possible in existing international environmental perception surveys.

BACKGROUND:Plastic pollution is a severe threat to marine ecosystems. While some microbial enzymes can degrade certain plastics, the ability of the global ocean microbiome to break down diverse environmental plastics remains limited. We employed metatranscriptomic data from an international ocean survey to explore global and regional patterns in microbial plastic degradation potential.RESULTS:On a global oceanic scale, we found no significant correlation between levels of plastic pollution and the expression of genes encoding enzymes putatively identified as capable of plastic degradation. Even when looking at different regional scales, ocean depth layers, or plastic types, we found no strong or even moderate correlation between plastic pollution and relative abundances of transcripts for enzymes with presumed plastic biodegradation potential. Our data, however, indicate that microorganisms in the Southern Ocean show a higher potential for plastic degradation, making them more appealing candidates for bioprospecting novel plastic-degrading enzymes.CONCLUSION:Our research contributes to understanding the complex global relationship between plastic pollution and microbial plastic degradation potential. We reveal that the transcription of putative plastic-degrading genes in the global ocean microbiome does not correlate to marine plastic pollution, highlighting the ongoing danger that plastic poses to marine environments threatened by plastic pollution.

The fragmentation of plastic debris is a key pathway to the formation of microplastic pollution. These disintegration processes depend on the materials' physical and chemical characteristics, but insight into these interrelationships is still limited, especially under natural conditions. Five plastics of known polymer/additive compositions and processing histories were deployed in aquatic environments and recovered after six and twelve months. The polymer types used were linear low density polyethylene (LLDPE), oxo-degradable LLDPE (oxoLLDPE), poly(ethylene terephthalate) (PET), polyamide-6 (PA6), and poly(lactic acid) (PLA). Four geographically distinct locations across Aotearoa/New Zealand were chosen: three marine sites and a wastewater treatment plant (WWTP). Accelerated UV-weathering under controlled laboratory conditions was also carried out to evaluate artificial ageing as a model for plastic degradation in the natural environment. The samples' physical characteristics and surface microstructures were studied for each deployment location and exposure time. The strongest effects were found for oxoLLDPE upon artificial ageing, with increased crystallinity, intense surface cracking, and substantial deterioration of its mechanical properties. However, no changes to the same extent were found after recovery of the deployed material. In the deployment environments, the chemical nature of the plastics was the most relevant factor determining their behaviours. Few significant differences between the four aquatic locations were identified, except for PA6, where indications for biological surface degradation were found only in seawater, not the WWTP. In some cases, artificial ageing reasonably mimicked the changes which some plastic properties underwent in aquatic environments, but generally, it was no reliable model for natural degradation processes. The findings from this study have implications for the understanding of the initial phases of plastic degradation in aquatic environments, eventually leading to microplastics formation. They can also guide the interpretation of accelerated laboratory ageing for the fate of aquatic plastic pollution, and for the testing of aged plastic samples.

The presence and persistence of microplastics (MPs) in diverse aquatic environments are of global concern. Microplastics can impact marine organisms via direct physical interaction and the release of potentially harmful chemical additives incorporated into the plastic. These chemicals are physically bound to the plastic matrix and can leach out. The hazards associated with chemical additives to exposed organisms is not well characterized. We investigated the hazards of plastic additives leaching from plastic. We used the common plasticizer dibutyl phthalate (DBP) as a chemical additive proxy and the New Zealand green-lipped mussel (Perna canaliculus) as a model. We used early-adult P. canaliculus exposed to combinations of virgin and DBP-spiked polyvinyl chloride (PVC), MPs, and DBP alone for 7 days. Whole transcriptome sequencing (RNA-seq) was conducted to assess whether leaching of DBP from MPs poses a hazard. The differences between groups were evaluated using pairwise permutational multivariate analysis of variance (PERMANOVA), and all treatments were significantly different from controls. In addition, a significant difference was seen between DBP and PVC MP treatment. Transcriptome analysis revealed that mussels exposed to DBP alone had the most differentially expressed genes (914), followed by PVC MP + DBP (448), and PVC MP (250). Gene ontology functional analysis revealed that the most enriched pathway types were in cellular metabolism, immune response, and endocrine disruption. Microplastic treatments enriched numerous pathways related to cellular metabolism and immune response. The combined exposure of PVC MP + DBP appears to cause combined effects, suggesting that DBP is bioavailable to the exposed mussels in the PVC MP + DBP treatment. Our results support the hypothesis that chemical additives are potentially an important driver of MP toxicity. Environ Toxicol Chem 2024;43:1604-1614. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Replanting is an important tool for ecological recovery. Management strategies, such as planting areas with monocultures or species mixtures, have implications for restoration success. We used 16S and ITS rRNA gene amplicon sequencing and shotgun metagenomics to assess how the diversity of neighboring tree species impacted soil bacterial and fungal communities, and their functional potential, within the root zone of manuka ( Leptospermum scoparium ) trees. We compared data from monoculture and mixed tree species plots and confirmed that soil microbial taxonomic and functional community profiles significantly differed ( p < 0.001). Compared to the diversity of neighboring tree species within the plot, soil environmental conditions and geographic distance was more important for structuring the microbial communities. The bacterial communities appeared more impacted by soil conditions, while the fungal communities displayed stronger spatial structuring, possibly due to wider bacterial dispersal. The different mechanisms structuring bacterial and fungal communities could have implications for ecological restoration outcomes.