Project description:Direct, untargeted sequencing of environmental samples (metagenomics) and de novo genome assembly enable the study of uncultured and phylogenetically divergent organisms. However, separating individual genomes from a mixed community has often relied on the differential-coverage analysis of multiple, deeply sequenced samples. In the metagenomic investigation of the marine bryozoan Bugula neritina, we uncovered seven bacterial genomes associated with a single B. neritina individual that appeared to be transient associates, two of which were unique to one individual and undetectable using certain "universal" 16S rRNA primers and probes. We recovered high quality genome assemblies for several rare instances of "microbial dark matter," or phylogenetically divergent bacteria lacking genomes in reference databases, from a single tissue sample that was not subjected to any physical or chemical pre-treatment. One of these rare, divergent organisms has a small (593 kbp), poorly annotated genome with low GC content (20.9%) and a 16S rRNA gene with just 65% sequence similarity to the closest reference sequence. Our findings illustrate the importance of sampling strategy and de novo assembly of metagenomic reads to understand the extent and function of bacterial biodiversity.
Project description:Polycyclic Aromatic Hydrocarbons (PAHs) continue to cause environmental challenges due to their release in the environment by a great variety of anthropogenic activities and their accumulation in soil ecosystems. Here we studied the toxicological effect of the model PAH phenanthrene (Phe) on the soil invertebrate model Enchytraeus crypticus at the individual, tissue and molecular level. Organisms were exposed to Phe for 2 and 21 days to the (previously estimated) EC10 and EC50 (population reproduction over 3 weeks). Gene expression profiling did not reveal a typical Phe-induced biotransfor-mation signature, as it usually does in arthropods and vertebrates. Instead, we observed only general metabolic processes to be affected after 2 days of exposure, such as translation and ATP synthesis-coupled electron transport. Histological sections of tissues of 2-day exposed animals did not show any deviations from the control situation. In contrast, prolonged exposure up to 21 days showed histopathological effects: chloragogenous cells were highly vacuolated and hypertrophic. This was corroborated by differential expression of genes related to immune response and oxidative stress at the transcriptomic level. The data exemplify the complexity and species-specific features of PAH toxicity among soil invertebrate communities, which restricts read-across and extrapolation in the context of soil ecological risk assessment.
Project description:Polycyclic Aromatic Hydrocarbons (PAHs) continue to cause environmental challenges due to their release in the environment by a great variety of anthropogenic activities and their accumulation in soil ecosystems. Here we studied the toxicological effect of the model PAH phenanthrene (Phe) on the soil invertebrate model Enchytraeus crypticus at the individual, tissue and molecular level. Organisms were exposed to Phe for 2 and 21 days to the (previously estimated) EC10 and EC50 (population reproduction over 3 weeks). Gene expression profiling did not reveal a typical Phe-induced biotransfor-mation signature, as it usually does in arthropods and vertebrates. Instead, we observed only general metabolic processes to be affected after 2 days of exposure, such as translation and ATP synthesis-coupled electron transport. Histological sections of tissues of 2-day exposed animals did not show any deviations from the control situation. In contrast, prolonged exposure up to 21 days showed histopathological effects: chloragogenous cells were highly vacuolated and hypertrophic. This was corroborated by differential expression of genes related to immune response and oxidative stress at the transcriptomic level. The data exemplify the complexity and species-specific features of PAH toxicity among soil invertebrate communities, which restricts read-across and extrapolation in the context of soil ecological risk assessment. The data presented in our manuscript is an exposure experiment where E. cryticus is exposed to phenanthrene EC10 and EC50 on reproduction for 2 and 21 days. A single channel, interwoven loop design was used to test animals. 4 biological replicates per condition were used containing 25 grams of soil and 5 - 7, adult old animals per replicate. The platform is a 4*180k Agilent platform containing some 86k E. crypticus probes in duplicate. However, only a subset of the probes (23k) was used for the analysis. To see which probes were used in the analysis see the raw data files control type column, only probes which are denoted with a 0 were used.
Project description:The microbiome associated with an animal's gut and other organs is considered an integral part of its ecological functions and adaptive capacity. To better understand how microbial communities influence activities and capacities of the host, we need more information on the functions that are encoded in a microbiome. Until now, the information about soil invertebrate microbiomes is mostly based on taxonomic characterization, achieved through culturing and amplicon sequencing. Using shotgun sequencing and various bioinformatics approaches we explored functions in the bacterial metagenome associated with the soil invertebrate Folsomia candida, an established model organism in soil ecology with a fully sequenced, high-quality genome assembly. Our metagenome analysis revealed a remarkable diversity of genes associated with antimicrobial activity and carbohydrate metabolism. The microbiome also contains several homologs to F. candida genes that were previously identified as candidates for horizontal gene transfer (HGT). We suggest that the carbohydrate- and antimicrobial-related functions encoded by Folsomia's metagenome play a role in the digestion of recalcitrant soil-born polysaccharides and the defense against pathogens, thereby significantly contributing to the adaptation of these animals to life in the soil. Furthermore, the transfer of genes from the microbiome may constitute an important source of new functions for the springtail.