Beer Spoilage Ability of Lactic Acid Bacteria is a Plasmid-Encoded Trait

Abstract

Beer spoilage ability of lactic acid bacteria (LAB) is known to be a strain-specific trait, while some plasmid-encoded genes were identified in the past 15 years, which are considered to mediate hop tolerance and beer spoilage potential. By comparing up to 114 LAB genomes of brewery and non-brewery isolates, comprising well characterized beer spoiling and non-spoiling strains of the most hazardous LAB species, we investigated the role of plasmids for LAB beer spoilage ability in the context of experimental data. We identified a brewery-specific, plasmid-encoded and highly homologous (between species and strains) shared gene pool. This gene pool encodes for the already known hop tolerance genes horA and horC, but it is also enriched in genes related to cell envelope metabolism and modification, cation homeostasis, oxidative stress tolerance and pH homeostasis. While most of these genes are suggested to have an auxiliary role for beer spoilage potential, there are others, which are obligatory for LAB growth in beer. These genes include promising diagnostic marker genes for the targeted differentiation of beer-spoiling and non-spoiling LAB.