The Easter oyster, Crassostrea virginica, is an ecologically and economically important species native to the bays and estuaries all along the western Atlantic. However, it has declined to <10% of its pre-industrial numbers and faces further decline due to a combination of overharvesting, habitat destruction, climate change and disease. While efforts have been made to restore the population, a lack of knowledge about the oyster’s genetics and physiology presents an ongoing barrier to restoration. We turned to the microbiome present in the oyster’s extrapallial fluid (EPF) to learn more about this animal’s health and fitness, particularly in light of environmental stress including ocean acidification. Through a combination of marker gene and bacterial metatranscriptome sequencing, we found that the extrapallial fluid harbors a rich core bacterial community which is distinct from the surrounding water and plays potential roles in shell calcification and in pollutant bioremediation and nutrient (C, N, S) cycling both in the host and the environment. Using a limited panel of 36 single nucleotide polymorphisms (SNPs) we also found 7 host genetic markers which correlate with microbiome composition, suggesting that host genetics plays a role in shaping this community. This community is also resilient to low pH stress, suggesting that it is stable, self-sustaining, and able to carry out its role even during ocean acidification. Additional metagenomic studies and genome-wide association studies utilizing now-available C. virginica SNP microarrays may further elucidate this community’s role in host health and pave the way for future restoration-oriented interventions such as the development of probiotic treatments, microbial biomarkers to assess host health, and targeted breeding or genetic engineering guided by better knowledge of the relationship between host genotype and the Eastern oyster microbiome.
Zahorik A., 2023. The microbiome of the eastern oyster, Crassostrea virginica, in health, disease and environmental stress. PhD thesis, University of Delaware. Thesis (restricted access).
