Water chlorination increases the relative abundance of an antibiotic resistance marker in developing sourdough starters

Abstract

Multiple factors explain the proper development of sourdough starters. While the role of raw ingredients and geography, among other things, have been widely studied recently, the possible effect of water chlorination on the overall bacterial communities associated with sourdough remains to be explored. Here, using 16s rRNA amplicon sequencing, we show that water chlorination at levels commonly found in drinking water systems has a limited impact on the overall bacterial communities developing in sourdough starters. However, using targeted sequencing, we found that the abundance of integron 1, a genetic mechanism responsible for the horizontal exchange of antibiotic resistance genes in spoilage and pathogenic bacteria, increased significantly with the level of water chlorination. While our results suggest that water chlorination might not impact sourdough starters at a deep phylogenetic level, they indicate that it can favor the growth of key spoilage bacteria.