Summary The necromenic nematode Pristionchus entomophagus has been frequently found in nests of the invasive European ant Myrmica rubra in coastal Maine, United States, and may contribute to ant mortality and collapse of colonies by transferring environmental bacteria. Paenibacillus and several other bacterial species were found in the digestive tracts of nematodes harvested from collapsed ant colonies. Serratia marcescens , Serratia nematodiphila , and Pseudomonas fluorescens were collected from the hemolymph of nematode-infected wax moth ( Galleria mellonella ) larvae. Virulence against waxworms varied by the site of origin of the nematodes. In adult nematodes, bacteria were highly concentrated in the digestive tract with none observed on the cuticle. In contrast, juveniles had more on the cuticle than in the digestive tract. Host species was the primary factor affecting bacterial community profiles, but Spiroplasma sp. and Serratia marcescens sequences were shared across ants, nematodes, and nematode-exposed G. mellonella larvae.
Motivation Environmental DNA (eDNA), as a rapidly expanding research field, stands to benefit from shared resources including sampling protocols, study designs, discovered sequences, and taxonomic assignments to sequences. High quality community shareable eDNA resources rely heavily on comprehensive metadata documentation that captures the complex workflows covering field sampling, molecular biology lab work, and bioinformatic analyses. There are limited sources that provide documentation of database development on comprehensive metadata for eDNA and these workflows and no open-source software. Results We present medna-metadata, an open-source, modular system that aligns with Findable, Accessible, Interoperable, and Reusable (FAIR) guiding principles that support scholarly data reuse and the database and application development of a standardized metadata collection structure that encapsulates critical aspects of field data collection, wet lab processing, and bioinformatic analysis. Medna-metadata is showcased with metabarcoding data from the Gulf of Maine (Polinski et al., 2019). Availability The source code of the medna-metadata web application is hosted on GitHub (https://github.com/Maine-eDNA/medna-metadata). Medna-metadata is a docker-compose installable package. Documentation can be found at https://medna-metadata.readthedocs.io/en/latest/?badge=latest. The application is implemented in Python, PostgreSQL and PostGIS, RabbitMQ, and NGINX, with all major browsers supported. A demo can be found at https://demo.metadata.maine-edna.org/. Supplementary information Supplementary data are available at Bioinformatics online.
Background:Necromenic nematode Pristionchus entomophagus has been frequently found in nests of the invasive European ant Myrmica rubra in coastal Maine, United States. The nematodes may contribute to ant mortality and collapse of colonies by transferring environmental bacteria. M. rubra ants naturally hosting nematodes were collected from collapsed wild nests in Maine and used for bacteria identification. Virulence assays were carried out to validate acquisition and vectoring of environmental bacteria to the ants.Results:Multiple bacteria species, including Paenibacillus spp., were found in the nematodes’ digestive tract. Serratia marcescens, Serratia nematodiphila, and Pseudomonas fluorescens were collected from the hemolymph of nematode-infected Galleria mellonella larvae. Variability was observed in insect virulence in relation to the site origin of the nematodes. In vitro assays confirmed uptake of RFP-labeled Pseudomonas aeruginosa strain PA14 by nematodes. Bacteria were highly concentrated in the digestive tract of adult nematodes, a small amount of bacteria were observed in the digestive tract of juveniles with a more significant amount on their cuticle, and none on the cuticle of adults. RFP-labeled P. aeruginosa were not observed in hemolymph of G. mellonella larvae, indicating an apparent lack of bacterial transfer from juvenile nematodes to the insects despite larval mortality.Host species was the primary factor affecting bacterial community profiles. Spiroplasma sp. and Serratia marcescens sequences were shared across ants, nematodes, and nematode-exposed G. mellonella larvae. Alternative to the idea of transferring bacteria from environment to host, we considered whether nematode-exposure might disorder or depauperate the endobiotic community of an insect host. While total bacterial diversity was not statistically lower in nematode-exposed G. mellonella larvae when compared to controls, 16 bacterial sequence variants were less abundant in nematode-exposed larvae, while three were increased, including Serratia, Pseudomonas, and Proteus.Conclusions: This study suggests that transfer of bacteria from nematodes to ants is feasible, although largely serendipitous, and may possibly contributed to ant death and/or collapse of wild colonies in Maine. Hypothetically, the use of an engineered biological control, such as nematodes carrying specifically-seeded bacterial species, may be effective, especially if the pathogenic bacteria are normally found in soil ecosystems and represents a low risk for biosafety control.
Infestations of commercially cultured eastern oysters (Crassostrea virginica) by shell-boring spionid polychaetes are common in the northeastern United States.Historically, infestations were attributed to Polydora websteri, also known as mud-blister worm. Among samples of shell-boring worms sampled from eight oyster farms in northern New England (Maine, New Hampshire, and Massachusetts), we detected P. websteri, as well as worms that were morphologically distinct from P. websteri. Using a combination of light and scanning electron microscopy, along with analysis of molecular variation at the nuclear 18S rRNA and mitochondrial cytochrome c oxidase I (COI) genes, we determined that specimens related to two other species of Polydora, Polydora onagawaensis and Polydora cornuta, were inhabiting burrows within the shells of oysters. Polydora cornuta is not recognized as a shell-boring species and likely invades existing burrows opportunistically. Our analysis of COI sequences identified three distinct genetic lineages among specimens morphologically identified as P. cornuta; one of these lineages is much more geographically widespread than previously had been reported. Polydora onagawaensis is considered a shell-boring species, and our article constitutes the first time this species has been documented in the Northwest Atlantic. We also provide evidence for three divergent COI genetic lineages that occur sympatrically among the specimens provisionally identified as P. onagawaensis in the northeastern United States.
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