Nematode-bacterial symbiosis is largely uncharted territory — there is so much to be discovered!

Plant-parasitic nematode stylet

Endosymbiont Xiphinematobacter within Xiphinema americanum nematode gut wall

Pratylenchus penetrans

Wheat

P. penetrans with endosymbiont Cardinium in yellow

Raspberry

Raspberry without nematicidal fumigant vs. with nematicide

Comparative gene repertoire of Wolbachia strains, including wPpe from P. penetrans

Cotton

Amino acid change in Wolbachia strains for various orthologous groups

Genome-skimming showing microbial associates of nematodes (in color)

Nematodes are (generally) tiny worms that are found in great numbers in most habitats on earth: in the oceans, freshwater, and soils, where they often feed on bacteria.

Many nematodes, however, are parasitic and cause serious diseases in plants, animals, and fungi. These parasitic nematodes tend to have limited diets — sometimes deficient in “animal-essential nutrients” (i.e. nutrients they cannot synthesize de novo). These insects also have other challenges, such as evading their host’s immune response or defending against other microbes.

As a consequence, some parasitic nematodes have become dependent on microbial partners for survival. We focus on plant-parasitic nematodes (PPNs) and their symbionts, such as those pictured above.

We are especially interested in using metagenomics and comparative genomics to study what these communities of nematode-associated microbes do, where they come from, how they vary to benefit or control pest PPNs.

Our recent publications in this area:

2021 Myers KN, Conn D, Brown AMV. Essential amino acid enrichment and positive selection highlight endosymbiont’s role in a global virus-vectoring pest. mSystems 6: e01048-20. doi: 10.1128/mSystems.01048-20

2019 Wasala SK, Brown AMV, Kang J, Howe DK, Peetz AB, Zasada IA, Denver DR. Variable abundance and distribution of Wolbachia and Cardinium endosymbionts in plant-parasitic nematode field populations. Frontiers in Microbiology 10:964. doi:10.3389/fmicb.2019.00964

2018 Howe DK, Smith M, Tom D, Brown AMV, Peetz AB, Zasada IA, Denver DR. Analysis of nematode-endosymbiont coevolution in the Xiphinema americanum species complex using molecular markers of variable evolutionary rates. Nematology (Online publication ahead of print Dec. 7, 2018)

2018 Brown AMV, Wasala SK, Howe DK, Peetz AB, Zasada IA, Denver DR. Comparative genomics of Wolbachia–Cardinium dual endosymbiosis in a plant-parasitic nematode. Frontiers in Microbiology 9:2482 PMC6232779

2018 Brown AMV. Endosymbionts of plant-parasitic nematodes. Annual Review of Phytopathology 56:225-242 doi.org/10.1146/annurev-phyto-080417-045824PMID:30149795

2016 Brown AMV, Wasala SK, Howe DK, Peetz AB, Zasada IA, Denver DR. Genomic evidence for plant-parasitic nematodes as the earliest Wolbachia hosts. Scientific Reports 6: 34955. doi:10.1038/srep34955

2016 Phillips WS, Brown AMV, Howe DK, Peetz AB, Blok VC, Denver DR, Zasada IA. The mitochondrial genome of Globodera ellingtonae is composed of two circles with segregated gene content and differential copy numbers. BMC Genomics 17:706. doi:10.1186/s12864-016-3047-x

2016 Denver DR, Brown AMV, Howe DK, Peetz AB, Zasada IA. Genome skimming: a rapid approach to gaining diverse biological insights into multicellular pathogens. PLoS Pathogens 12(8): e1005713. doi:10.1371/journal.ppat.1005713

2015 Brown AMV, Howe DK, Peetz AB, Wasala SK, Zasada IA, Denver DR. Comparative genomics of an endosymbiont in a plant-parasitic nematode suggest a role in nutritional symbiosis. Genome Biology & Evolution 7(9):2727-2746. doi:10.1093/gbe/evv176