Assessing contamination in DNA extraction kits commonly used for microbiome research

Sequencing-based measurements are now routinely used to investigate the microbial world, however, contamination by DNA outside the intended sample remains a problem. Contaminants obscure the true microbial signal and can lead to misleading scientific interpretations. Much work has been done to address the effects of these contaminants including best practices as outlined in Eisenhofer et al. and Fierer et al. Yet, even with best practices in place, the current literature consensus is that contaminants remain impactful, at least in low biomass environments (5, 7, 11, 13, 16). One well-known source of contaminants are those found within DNA extraction kits, as was shown clearly in the pioneering work of Salter et al. 2012 and Karstens et al. 2019. However, given the rapid evolution of DNA sequencing methods, it would be worthwhile to revisit the issue of contaminants in contemporary DNA extraction kits (the "kitome"). Here we provide an updated characterization of the kitomes of DNA extraction kits commonly used for microbiome research. ImportanceMicrobial contamination in commonly used DNA extraction kits has not been recently assessed. Here we evaluate the contamination in DNA extraction kits commonly used in microbiome studies over the past several years, and provide actionable guidance on appropriate DNA extraction kits for low biomass microbiome measurements.