Changes

[[File:Brussels brett blend pellicle1.jpg|thumb|Pellicle from The Yeast Bay Brussels Brett Blend; courtesy of Dan Pixley]][[File:Lactobacillus pellicle.jpg|thumb|Lactobacillus pellicle; courtesy of Matt Humbard]] A '''pellicle''' is an aggregation of cells, proteins, and long chain sugars (polysaccharides) formed on the surface of a beer. The "bubble" formations are caused by trapped CO2 beneath the pellicle structurefilm. Pellicles are often formed by [[Brettanomyces]], [[Pediococcus]], and [[Lactobacillus]], as well as ''Acetobacter spp'' <ref>[http://www.ncbi.nlm.nih.gov/pubmed/24559734 Pellicle of thermotolerant Acetobacter pasteurianus strains: characterization of the polysaccharides and of the induction patterns. Perumpuli PA, Watanabe T, Toyama H. Aug 2014.]</ref> and other gram-negative bacteria <ref name="Armitano">[http://www.ncbi.nlm.nih.gov/pubmed/25756106 Gram-negative bacteria can also form pellicles. Armitano J, Méjean V, Jourlin-Castelli C. Environ Microbiol Rep. 2014 Dec.]</ref>. It can also be formed by [[Saccharomyces]] in rare occasions <ref name="matt">[http://phdinbeer.com/2015/01/30/beer-microbiology-what-is-a-pellicle/ Beer Microbiology – What is a pellicle? A PhD in Beer blog. Dr. Matt Humbard. 01/30/2015. Retrieved 04/26/2015.]</ref>.