Brevibacterium from Austrian hard cheese harbor a putative histamine catabolism pathway and a plasmid for adaptation to the cheese environment

Abstract

<p>The genus <em>Brevibacterium</em> harbors many members important for cheese ripening. We performed real-time quantitative PCR (qPCR) to determine the abundance of <em>Brevibacterium</em> on rinds of Vorarlberger Bergkäse, an Austrian artisanal washed-rind hard cheese, over 160 days of ripening. Our results show that <em>Brevibacterium</em> are abundant on Vorarlberger Bergkäse rinds throughout the ripening time. To elucidate the impact of <em>Brevibacterium</em> on cheese production, we analysed the genomes of three cheese rind isolates, L261, S111, and S22. L261 belongs to <em>Brevibacterium aurantiacum</em>, whereas S111 and S22 represent novel species within the genus <em>Brevibacterium</em> based on 16S rRNA gene similarity and average nucleotide identity. Our comparative genomic analysis showed that important cheese ripening enzymes are conserved among the genus <em>Brevibacterium</em>. Strain S22 harbors a 22 kb circular plasmid which encodes putative iron and hydroxymethylpyrimidine/thiamine transporters. Histamine formation in fermented foods can cause histamine intoxication. We revealed the presence of a putative metabolic pathway for histamine degradation. Growth experiments showed that the three <em>Brevibacterium</em> strains can utilize histamine as the sole carbon source. The capability to utilize histamine, possibly encoded by the putative histamine degradation pathway, highlights the importance of <em>Brevibacterium</em> as key cheese ripening cultures beyond their contribution to cheese flavor production.</p>