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

Proper development of sourdough starters is critical for making tasty and healthy bread. Although many factors contributing to sourdough development have been studied, the effect of water chlorination on the bacterial communities in sourdough has been largely ignored. Researchers used sequencing techniques to investigate this effect and found 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, they discovered that water chlorination could increase the abundance of integron 1, a genetic mechanism responsible for the horizontal exchange of antibiotic resistance genes in spoilage and pathogenic bacteria. This suggests that water chlorination could favor the growth of key spoilage bacteria and compromise the quality and safety of the bread. These findings emphasize the importance of considering water quality when developing sourdough starters for the best possible bread.