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''Brettanomyces'' is known for not producing much glycerol in beer. [https://en.wikipedia.org/wiki/Glycerol Glycerol] is a colorless, sweet-tasting, viscous liquid that is thought to be an important contributor to the mouthfeel of beer. Glycerol is produced as a stress response by a wide range of microbes, including ''S. cerevisiae'', and various species and strains of ''Debaryomyces'', ''Candida'', ''Lachancea'', and ''Zygosaccharomyces''. Despite not producing amounts of glycerol that are perceivable in beer, some strains of ''Brettanomyces bruxellensis'' actually produce glycerol which is stored inside of their cells as a response to osmotic stress. They can also uptake glycerol into their cells. Doing so allows the cells to survive osmotic pressure <ref>[https://www.sciencedirect.com/science/article/pii/S0740002013001251?via%3Dihub Osmotic stress response in the wine yeast Dekkera bruxellensis. Silvia Galafassi, Marco Toscano, Ileana Vigentin, Jure Piškur, Concetta Compagno. 2013.]</ref><ref>[https://academic.oup.com/femsle/advance-article-abstract/doi/10.1093/femsle/fny020/4828327?redirectedFrom=fulltext Osmotolerance of Dekkera bruxellensis and the role of two Stl glycerol-proton symporters. Jana Zemančíková, Michala Dušková, Hana Elicharová, Klára Papoušková, Hana Sychrová. 2018.]</ref>. It is currently not known how many strains are capable of producing glycerol internally, or if this amount of glycerol has any impact on perceived mouthfeel of a beer if a substantial amount of ''Brettanomyces'' cells eventually autolyze (see [https://www.facebook.com/groups/MilkTheFunk/permalink/2003626776332193/ this MTF thread]). The role of glycerol in creating mouthfeel is debatable in the wine world <ref>[https://www.winesandvines.com/features/article/68760 Tim Patterson. "Many Roads to Mouthfeel". Wines & Vines Magazine. Nov 2009. Retrieved 03/23/2018.]</ref>.
The genetic diversity of ''Brettanomyces'' is particularly wide. For example, one study that analyzed the whole genomes of 53 strains of ''B. bruxellensis'' found that the overall genetic diversity between different strains of ''B. bruxellensis'' was higher than strains of ''S. cerevisiae'' (however, the entire gene set, known as the ''pangenome'', of all the genes among all of the strains of '''B. bruxellensis'' is much smaller than the entire gene set of ''S. cerevisiae'') <ref name="Gounot_2019" />. Some studies have indicated that strains of ''B. bruxellensis'' have adapted to specific environments. For example, one study found that strains of ''B. bruxellensis'' isolated from wine had 20 genes involved in the metabolism of carbon and nitrogen, whereas strains isolated from beer did not. This indicated that ''B. bruxellensis'' strains living in wine have adapted to the harsher environment of wine <ref name="smith_divol_2016"></ref>. Another study found that one out of the two strains tested that were isolated from soda could not ferment maltose, and only strains isolated from wine were able to grow in wine and the beer/soda strains did not. The wine strains were also more resistant to sulfites, which are commonly used in the wine industry to prevent microbial contamination <ref name="Crauwels_2016" />. The whole genome sequencing of one strain of ''B. naardenensis'' found that it was missing the genes associated with nitrate utilization, indicating that it is not well adapted to survive in beer where nitrates are abundant due to hops <ref name="Tiukova_2019" />.
A genetic survey of 145 different strains of ''B. bruxellensis'' from 29 countries, 5 continents, and 9 different fermentation niches was conducted in 2018 by Avramova et al. They found that these strains formed roughly 6 genetic groups with mostly separate ancestral lineages, and 1 group with a mixed ancestral lineage: 3 wine groups, 1 beer group, 1 kombucha group (most distantly related to the beer group), as well as 1 tequila/ethanol group that has multiple ancestral lineages <ref name="Avramova_2018" />. These groups are partially determined by the identification of at least two hybridization events that happened during the evolution of ''B. bruxellensis'', similar to the hybridization events that created the Saaz and Frohberg subgroups of ''S. pastorianus'' (the parents of these hybridization events in ''B. bruxellensis'', whether from different species or not, has yet to be determined and will require whole genome sequencing of species closely related to ''B. bruxellensis'') <ref name="Gounot_2019" />. This was expressed mostly in the ploidy level of each group (the number of sets of chromosomes), with 2 of the wine groups, the tequila group, and the beer group containing more sets of chromosome pairs than the other groups (diploid vs triploid; this is thought to encourage adaption and hybridization). Additionally, the triploid wine group was generally more tolerant of SO<sup>2</sup> than the diploid wine groups <ref name="Avramova_2018" />. A later study that also looked at the genome of older ''B. bruxellensis'' strains in bottles of wine going back as far as the year 1909 revealed that the SO<sup>2</sup> tolerant triploid strains only started appearing after the year 1990, which corresponds to when the wine industry started using SO<sup>2</sup> in most wine production (although it can also mean that the triploid strains are not as good at surviving in bottles of wine long-term compared to the diploid strains that have been isolated from much older bottles of wine; this will be determined to be the case or not in the future as bottles of wine from the 1990s continue to age). They also identified dozens of examples of wineries throughout France and Italy where the same strain of ''B. bruxellensis'' was found in multiple vintages of bottles of wine going back many decades, indicating that individual ''B. bruxellensis'' strains become long-term residents in wineries. Some identical strains have been found in different regions and even different continents, indicating that some strains have traveled not just due to traditional vectors such as insects or birds, but also probably due to human transportation such as wine bottle imports/exports or exchanges between industrial processes. This also indicates that while ''B. bruxellensis'' becomes rather sedentary and a constant resident in wineries, it can also adapt to the different winemaking conditions in different regions once it's been transported (different grapes, different climates, different fermentation temperatures, etc.), including adapting to improved modern hygienic practices such as higher SO<sup>2</sup> treatment. Overall, the results from this study suggest that ''Brettanomyces'' is able to adapt to living alongside certain human industries and has done so for at least a couple of centuries <ref name="Cibrario_2019">[https://www.biorxiv.org/content/10.1101/763441v1 Brettanomyces bruxellensis wine isolates show high geographical dispersal and long remanence in cellars. Alice Cibrario, Marta Avramova, Maria Dimopoulou, Maura Magani, Cécile Miot-Sertier, Albert Mas, Maria C. Portillo, Patricia Ballestra, View ORCID ProfileWarren Albertin, Isabelle Masneuf-Pomarede, Marguerite Dols-Lafargue. 2019. DOI: https://doi.org/10.1101/763441.]</ref>. The genetic differences between the fermentation substrates (beer, wine, etc.) were lower but still significant, and this was explained by the frequent cross-over of equipment such as wine barrels being used for beer fermentation. When comparing the geographic differences, they found geography contributed only 5% of genetic differences, while geography explained more than 50% of genetic differences in non-wine strains, suggesting that beer, kombucha, and tequila strains are more localized genetically than wine strains and that humans probably helped the wine strains travel across the globe. They also found that although one study reported spore-forming versions of ''B. bruxellensis'' (referred to as ''Dekkera bruxellensis''), the genetic makeup of the analyzed strains determined their ability to sporulate to be non-existent or rare (only one study that we know of by [https://link.springer.com/article/10.1007%2FBF02539015 Walt and Kerken in 1960] has reported sporulation in ''Brettanomyces'' only on specific agar types with vitamins added, indicating that sporulation in ''Brettanomyces'' is extremely rare) <ref name="Avramova_2018" />. See also [https://www.facebook.com/groups/MilkTheFunk/permalink/2022801681081369/ Richard Preiss's discussion of this study on MTF].