Six of L. brevis strains were sequenced and compared. Comparative genomics of hop tolerant and sensitive Lactobacillus brevis isolated from beer

Hop tolerance is a prerequisite for beer spoilage bacteria. Lactobacillus brevis is the major spoiler in beer, affecting beer quality and causing economic losses in breweries. Although several hop resistant genes have been identified, controversies still exist about the number of, and role of, genes associated with growth in beer. In this study, 21 L.brevis were screened for hop tolerance and three hop tolerant as well as two hop-acid sensitive strains were selected for further investigation. Furthermore, one tolerant strain was plasmid-cured rendering it sensitive as determined by growth experiments. Whole genome sequencing of the five strains and the plasmid-cured strain was performed and followed by in-depth comparative genomics analysis between the tested strains as well as between the tested strains and previously published L.brevis genomes. The physiological differences between the tolerant wildtype and the sensitive variant allowed for the identification of chromosome- and plasmid-borne features, which contribute to hop tolerance. In addition, several new genes associated with growth in hop containing media were detected by the genomic comparison of tolerant versus sensitive strains. These genes could serve as additional marker genes to detect very potent spoilage bacteria in breweries. Our findings underline the notion that the ability to grow in beer, which is a hostile environment (low pH, hop-acid, ethanol), is a multi-factorial property, and therefore requires a combination of several marker genes and techniques like multiplex-PCR to predict the spoilage potential of L.brevis in breweries.