13,703
edits
Changes
m
no edit summary
As with some things in science that are not greatly explored, terminology isn't always agreed upon or fully established, and thus researching such a topic without a lot of prior knowledge can be challenging. Pellicles are a good example of this. It is sometimes stated that a pellicle is a type of biofilm. However, the widely accepted definition of a "biofilm" in biology refers to something specifically different. A [http://www.biofilm.montana.edu/node/2390 biofilm] in microbiology is an aggregate of microorganisms where the cells adhere to each other on a solid surface <ref>[https://books.google.com/books?id=-ZDKAQAAQBAJ&pg=PT87&lpg=PT87&dq=brock+microbiology+biofilm&source=bl&ots=PwNZ20KFqq&sig=19lvlfqYj8bE7roiA7g4oJ3Xl0E&hl=en&sa=X&ved=0CCcQ6AEwAWoVChMImZaUmN_AxwIVVFmICh1pQgk0#v=onepage&q=brock%20microbiology%20biofilm&f=false e-Study Guide for Brock Biology of Microorganisms, textbook by Michael T. Madigan.]</ref>. Examples of biofilms are dental plaque and the green film produced by algae that covers stones in water streams <ref name="montana">[http://www.biofilm.montana.edu/node/2390 Center For Biofilm Engineering. Montona State University. Retrieved 09/05/2015.]</ref>. Biofilms are encountered in brewing in the form of contaminating microorganisms and poor cleaning/sanitation techniques. Biofilms are a common source of persistent brewhouse infections and can be resistant to the actions of many cleaning and sanitizing agents <ref name="montana"></ref><ref name="Bryan">Private conversation with Dr. Bryan Heit.</ref>. Pellicles in beer do not attach to a solid surface, they appear on the "air-liquid interface" (the surface of the beer). They are also not colonies within an adhesive <ref name="Bryan">[https://www.facebook.com/groups/MilkTheFunk/permalink/1131334646894748/?comment_id=1131986723496207&offset=0&total_comments=57&comment_tracking=%7B%22tn%22%3A%22R3%22%7D Conversation with Bryan Heit about Pellicles on MTF. 08/20/2015.] </ref>. To make matters even more confusing, the two widely accepted definitions of a "pellicle" in biology are the outer boundary of a protozoa cell <ref>[https://books.google.com/books?id=ACBcDjDLuNAC&pg=PA38&lpg=PA38&dq=pellicle+biology&source=bl&ots=58e43A_9h-&sig=ViakT4Ectu4DOlqoSWRCPFJ73iw&hl=en&sa=X&sqi=2&ved=0CGIQ6AEwDGoVChMIp6WkouTAxwIVgpmICh0F1wXO#v=onepage&q=pellicle%20biology&f=false Biology of Protozoa. D.R. Khanna. Discovery Publishing House, Jan 1, 2004. Pg 38.]</ref>, and the protein film that forms on the surface of teeth <ref>[https://en.wikipedia.org/wiki/Dental_pellicle Wikipedia. Dental Pellicle. Retrieved 08/23/2015.]</ref>.
The usage of the term "biofilm" has been used to describe the layer of film that covers sherry known as "Flor" <ref>[http://aem.asm.org/content/76/12/4089.full Ethanol-Independent Biofilm Formation by a Flor Wine Yeast Strain of Saccharomyces cerevisiae. Severino Zara, Michael K. Gross, Giacomo Zara, Marilena Budroni and Alan T. Bakalinsky. 2010.]</ref><ref>[http://femsle.oxfordjournals.org/content/femsle/237/2/425.full.pdf FLO11 is essential for flor formation caused by the C-terminal deletion of NRG1 in Saccharomyces cerevisiae. Mari Ishigami, Youji Nakagawa, Masayuki Hayakawa, Yuzuru Iimura. 2004.]</ref>. The word "pellicle" generally isn't used, although it has appeared on occasion when referring to sherry flor in the 1960's <ref>[http://www.ncbi.nlm.nih.gov/pubmed/5311988 On the pellicle formation by “flor” yeasts. Cantarelli C, Martini A. Antonie Van Leeuwenhoek. 1969.]</ref>. More recently, there have been studies that define a "pellicle" like we see in fermentation as a type of biofilm that forms on the air-liquid interface of a liquid (see references) <ref name="Armitano"></ref><ref>[http://www.ncbi.nlm.nih.gov/pubmed/26122431 Motility, Chemotaxis and Aerotaxis Contribute to Competitiveness during Bacterial Pellicle Biofilm Development. Hölscher T, Bartels B, Lin YC, Gallegos-Monterrosa R, Price-Whelan A, Kolter R, Dietrich LE, Kovács ÁT. J Mol Biol. 2015 Jun 26.]</ref><ref>[http://www.ncbi.nlm.nih.gov/pubmed/24035282 Modulation of curli assembly and pellicle biofilm formation by chemical and protein chaperones. Andersson EK, Bengtsson C, Evans ML, Chorell E, Sellstedt M, Lindgren AE, Hufnagel DA, Bhattacharya M, Tessier PM, Wittung-Stafshede P, Almqvist F, Chapman MR. Chem Biol. 2013 Oct 24.]</ref><ref>[http://www.horadent.com/uploads/media/2005_Branda.pdf Biofilms: the matrix revisited. Steven S. Branda, Ashild Vik, Lisa Friedman and Roberto Kolter. Jan 2005.]</ref><ref>[http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2958.2003.03877.x/full Genes involved in matrix formation in Pseudomonas aeruginosa PA14 biofilms. Lisa Friedman andRoberto Kolter. Dec 2003.]</ref>. However, according to Dr. Bryan Heit, the use (or misuse) of the term "biofilm" in these few studies does not warrant a change in the already established definition of the term <ref name="Bryan"></ref>.
The importance of understanding this terminology becomes apparent when trying to research the topic of pellicles in beer. Currently they have not been studied much at all, whereas pellicles of dentistry and microbiology have been studied in depth, as well as biofilms. Thus, brewers should take care when researching scientific publications.