Role of the intestinal microbiome in low-density polyethylene degradation by caterpillar larvae of the greater wax moth, Galleria mellonella.

Recently, a few insects, including the caterpillar larva of the greater wax moth Galleria mellonella, have been identified as avid 'plastivores'. These caterpillars are able to ingest and metabolize polyethylene at unprecedented rates. While it appears that G. mellonella plays an important role in the biodegradation process, the contribution of its intestinal microbiome remains poorly understood and contested. In a series of experiments, we present strong evidence of an intricate relationship between an intact microbiome, low-density polyethylene (LDPE) biodegradation and the production of glycol as a metabolic by-product. First, we biochemically confirmed that G. mellonella larvae consume and metabolize LDPE, as individual caterpillars fed on polyethylene excreted glycol, but those excretions were reduced by antibiotic treatment. Further, while the gut bacterial communities remained relatively stable regardless of diet, we showed that during the early phases of feeding on LDPE (24-72 h), caterpillars exhibited increased microbial abundance relative to those starved or fed on their natural honeycomb diet. Finally, by isolating and growing gut bacteria with polyethylene as their exclusive carbon source for over 1 year, we identified microorganisms in the genus Acinetobacter that appeared to be involved in this biodegradation process. Taken collectively, our study indicates that during short-term exposure, the intestinal microbiome of G. mellonella is intricately associated with polyethylene biodegradation in vivo.

Proteomic Analysis of Chicken Chorioallantoic Membrane (CAM) during Embryonic Development Provides Functional Insight.

In oviparous animals, the egg contains all resources required for embryonic development. The chorioallantoic membrane (CAM) is a placenta-like structure produced by the embryo for acid-base balance, respiration, and calcium solubilization from the eggshell for bone mineralization. The CAM is a valuable in vivo model in cancer research for development of drug delivery systems and has been used to study tissue grafts, tumor metastasis, toxicology, angiogenesis, and assessment of bacterial invasion. However, the protein constituents involved in different CAM functions are poorly understood. Therefore, we have characterized the CAM proteome at two stages of development (ED12 and ED19) and assessed the contribution of the embryonic blood serum (EBS) proteome to identify CAM-unique proteins. LC/MS/MS-based proteomics allowed the identification of 1470, 1445, and 791 proteins in CAM (ED12), CAM (ED19), and EBS, respectively. In total, 1796 unique proteins were identified. Of these, 175 (ED12), 177 (ED19), and 105 (EBS) were specific to these stages/compartments. This study attributed specific CAM protein constituents to functions such as calcium ion transport, gas exchange, vasculature development, and chemical protection against invading pathogens. Defining the complex nature of the CAM proteome provides a crucial basis to expand its biomedical applications for pharmaceutical and cancer research.

Transcriptional effects of polyethylene microplastics ingestion in developing zebrafish (Danio rerio).

Over the last few decades, plastic waste has become an increasing environmental concern as it accumulates in every environment on our planet. Though traditionally seen as a macroscopic problem (i.e., large plastic debris), plastic pollution is also evident at smaller scales. Indeed, the intentional industrial production of small plastic particles and the physical degradation of larger plastic debris have overtime resulted in an increased environmental prevalence of smaller plastic particles, including microplastics. While the effects of these small polymers on marine biota have been an important research focus, recent global surveys indicate that our freshwater lakes and rivers are also plagued by microplastics. However, despite these discoveries we currently have a limited understanding of the impact these particles may have on freshwater animals, particularly on vertebrate species. Thus, the aim of the present study was to assess the impact of high concentrations of microplastics (5 and 20 mg.L-1) on the early life stages in zebrafish, a model freshwater vertebrate model. To do this, we exposed embryonic and larval zebrafish to fluorescently labelled polyethylene microspheres for up to 14 days and assessed their microplastic content, growth, hatching and oxygen consumption rates. We then explored the molecular underpinnings of the microplastic response by RNA sequencing. Over the course of the exposure, we observed a consistent accumulation of microplastics in the gastrointestinal tract of the fish in a concentration dependent manner, but could not detect any detrimental effects of these particles on larval development, growth or metabolism. However, whole animal transcriptomics revealed that microplastics induced a transient and extensive change in larval gene expression within 48 h exposure, which largely disappeared by 14 days. However, as these transcriptional changes occurred during a critical period of larval development, we suggest that an evaluation of the potential long-term impact of these particles is warranted.