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'''Pediococcus''' (often referred to by brewers as "Pedio") are Gram-positive lactic acid bacteria (LAB) used in the production of Belgian style beers where additional acidity is desirable. They are native to plant material and fruits <ref name="ucdavis">[http://wineserver.ucdavis.edu/industry/enology/winemicro/winebacteria/pediococcus_damnosus.html Viticulture & Enology. UC Davis website. Pedioccous damnosus. Retreived 07/28/2015.]</ref>, and often found in spontaneously fermented beer as the primary source of lactic acid production (with ''P. damnosus'' being the only species identified in lambic) <ref>[http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0095384 The Microbial Diversity of Traditional Spontaneously Fermented Lambic Beer. Freek Spitaels, Anneleen D. Wieme, Maarten Janssens, Maarten Aerts, Heide-Marie Daniel, Anita Van Landschoot, Luc De Vuyst, Peter Vandamme. April 18, 2014.]</ref><ref>[[Scientific_Publications#Lambic_and_Spontaneous_Fermentation|Multiple Scientific publications linked on MTF.]]</ref>. The ability to grow in beer is strain dependent rather than species dependent, however genetic differences indicate that ''P. damnosus'' and ''P. claussenii'' are better adapted to surviving in beer than ''P. pentosaceus'' <ref name="Snauwaert">[http://www.biomedcentral.com/content/pdf/s12864-015-1438-z.pdf Comparative genome analysis of Pediococcus damnosus LMG 28219, a strain well-adapted to the beer environment. Isabel Snauwaert, Pieter Stragier, Luc De Vuyst and Peter Vandamme. 2015.]</ref>. Like many bacteria, Pediococci have the ability to [https://en.wikipedia.org/wiki/Horizontal_gene_transfer transfer genes horizontally] without reproduction <ref name="Snauwaert"></ref>. They are generally considered to be facultative anaerobes, which means they grow anaerobically but can also grow in the presence of oxygen <ref>[http://textbookofbacteriology.net/lactics.html Lactic Acid Bacteria. Todar's Online Texbook of Bacteriology. Kenneth Todar, PhD. Pg 1. Retrieved 08/09/2015.]</ref>. Some species/strains (including individual strains of ''P. damnosus'') can have their growth and acid production inhibited by oxygen <ref>[The Journal of General and Applied Microbiology https://www.jstage.jst.go.jp/article/jgam1955/5/3/5_3_95/_article TAXONOMIC STUDIES ON THE GENUS PEDIOCOCCUS. ATSUSHI NAKAGAWA, KAKUO KITAHARA. 1959.]</ref>, while some will have better growth and produce more acid in the presence of oxygen (microaerophilic) <ref>[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC357257/ THE NUTRITION AND PHYSIOLOGY OF THE GENUS PEDIOCOCCUS. Erling M. Jensen and Harry W. Seeley. 1954.]</ref><ref>[http://www.microbialcellfactories.com/content/8/1/3#B5 Pediocins: The bacteriocins of Pediococci. Sources, production, properties and applications. Maria Papagianni and Sofia Anastasiadou. 2009.]</ref>. Strains found in beer are hop tolerant <ref>[http://www.biomedcentral.com/1471-2164/16/267 Comparative genome analysis of Pediococcus damnosus LMG 28219, a strain well-adapted to the beer environment. Isabel Snauwaert, Pieter Stragier, Luc De Vuyst and Peter Vandamme. April 2015.]</ref>. Due to their continued metabolism of longer chain polysaccharides, acid production will increase with storage time. ''Pediococcus'' can form a [[pellicle]].