Identification of ecotype-specific marker genes for categorization of beer-spoiling Lactobacillus brevis.

The tolerance to hop compounds, which is mainly associated with inhibition of bacterial growth in beer, is a multi-factorial trait. Any approaches to predict the physiological differences between beer-spoiling and non-spoiling strains on the basis of a single marker gene are limited. We identified ecotype-specific genes related to the ability to grow in Pilsner beer via comparative genome sequencing. The genome sequences of four different strains of Lactobacillus brevis were compared, including newly established genomes of two highly hop tolerant beer isolates, one strain isolated from faeces and one published genome of a silage isolate. Gene fragments exclusively occurring in beer-spoiling strains as well as sequences only occurring in non-spoiling strains were identified. Comparative genomic arrays were established and hybridized with a set of L. brevis strains, which are characterized by their ability to spoil beer. As result, a set of 33 and 4 oligonucleotide probes could be established specifically detecting beer-spoilers and non-spoilers, respectively. The detection of more than one of these marker sequences according to a genetic barcode enables scoring of L. brevis for their beer-spoiling potential and can thus assist in risk evaluation in brewing industry.

Lactobacillus paucivorans sp. nov., isolated from a brewery environment.

A Gram-stain-positive, catalase-negative and rod-shaped bacterium was isolated from a brewery environment. Its phylogenetic affiliation was determined by using 16S rRNA gene sequence analysis. It was found that strain TMW 1.1424(T) belongs to the genus Lactobacillus, with the three nearest neighbours Lactobacillus parabrevis LMG 11984(T) (97 %), Lactobacillus brevis DSM 20054(T) (95.9 %) and Lactobacillus hammesii DSM 16381(T) (96.2 %). Comparative sequencing of additional phylogenetic marker genes tuf and pheS confirmed the 16S rRNA gene sequence tree topology. The DNA G+C content of strain TMW 1.1424(T) is 46.6 mol%. Genomic DNA-DNA relatedness values with L. brevis DSM 20054(T), L. parabrevis LMG 11984(T) and L. hammesii DSM 16381(T) do not exceed 52.8 %, revealing that the novel isolate represents a separate genomic species. The strain can be distinguished from other related species of the genus Lactobacillus by physiological and biochemical tests. Based on biochemical, physiological and phylogenetic data, it is proposed that the new isolate be classified as a novel species of the genus Lactobacillus, Lactobacillus paucivorans sp. nov. The type strain is TMW 1.1424(T) (=DSM 22467(T) =LMG 25291(T)).