Diversity, relatedness and maintenance of BSR LAB
General LAB characteristics
Problematic BSR LAB and sour-beer fermenting LAB alike traditionally belong to the Firmicutes phylum, order Lactobacillales, in the genera Lactobacillus and Pediococcus (Priest, 2003), with
Lactobacillus brevis, Lactobacillus linderni and Pediococcus damnosus being the most commonly encountered bacteria that spoil beer (Back, 2005; Menz et al., 2010; Priest, 2003; Suzuki, 2008; Thelen et al., 2006). Additional LAB species also have been detected with varying frequencies in brewing environments, including Lactobacillus amylolyticus (Bohak et al., 1998), Lactobacillus backii (Bohak et al., 2006), Lactobacillus brevisimilis (Back, 1987), Lactobacillus buchneri, Lactobacillus casei, Lactobacillus coryneformis, Lactobacillus curvatus, Lactobacillus delbrueckii (Priest, 2003), Lactobacillus dextrinicus (Haakensen et al., 2009a), Lactobacillus fermentum, Lactobacillus fruc- tivorans, Lactobacillus malefermentans (Russell and Walker, 1953), Lactobacillus parabuchneri, (Priest, 2003), Lactobacillusparacollinoides (Suzuki, 2004), Lactobacillus plantarum (Priest, 2003; Thelen et al.,
- 2006), Lactobacillus paraplantarum (Curk et al.,
- 1996), Lactobacillus paucivorans (Ehrmann et al., 2010), Lactobacillus rossiae (Corsetti et al., 2005), Pediococcus claussenii (Dobson et al., 2002), Pediococcus inopinatus, Pediococcus parvulus (Martens et al., 1997) and Pediococcus pentosaceous ( Jespersen and Jakobsen, 1996).
Despite the reported incidence of certain species within breweries, it must be emphasized that the ability for BSR LAB to grow in and spoil beer is not a species attribute, but is an isolate-specific capability, as is the case for most spoilage lactobacilli (Sanders et al., 2015). As this phenomenon indicates that there must be a level of genetic specialization in a BSR LAB isolate that allows for the beer spoilage phenotype, the search for a small number of ‘detectable' genetic markers has long been the focus of analysis. However, this narrow scope of investigation fails to appreciate the degree of genetic dissimilarity inherent among BSR LAB given that these isolates belong to the LAB group as a result of shared functional characteristics (i.e. particular metabolic capacities) and not necessarily genetic relatedness among LAB (Sun et al., 2014). Additionally, the use of ‘common' BSR LAB isolates for the study of genetic differences probably produces results that are non-universal for BSR LAB. Common isolates are those that can grow in routine culture media, and are thus probably consistently over-represented during detection procedures (Suzuki et al., 2008). Given that not all Lactobacillus and Pediococcus isolates can grow in these media, those that can likely skew incidence reports of beer spoilage, and therefore the amount of research interest and available information on BSR LAB.