Genomic and physiological characterization of beer spoiling Megasphaera spp.

Beer spoiling bacteria represent a major concern for the brewing industry. Anaerobic spoilers of the genus Megasphaera are especially dreadful. Until now, the genome analysis of Megasphaera spp. was limited to mammal-associated species, yet beer borne Megasphaera species and their abilities to tolerate the multiple high stress factors in their niche were broadly overlooked. This study is the first to carry out an in silico genome comparison of ten strains from three different beer spoiling Megasphaera species ( M. cerevisiae , M. paucivorans and M. sueciensis ). We experimentally show a hitherto unseen resilience of beer spoiling Megasphaera strains, which can grow in lager beer with an isoα-acids content of up to 120 IBU, an ethanol concentration of up to 7.0 % ( v /v) and at pH 4.0. The genomes revealed genes appearing to aid survival in the harsh brewing environment mainly comprised of hop, ethanol and acid stress. • First genome comparison of beer spoiling Megasphaera spp. • Shown tolerance towards hop stress of up to 120 ppm isoα-acids, 7.0 % ( v /v) ethanol stress and a pH of 4.0. • Several hop transporter homologs (HitA, HorA and Nramp) found in all genomes