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# Scientific research on pellicle formation in beer is currently next to none.
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An often asked question by homebrewers is can a contaminating or wild caught microbe be identified based on the appearance of a pellicle. This is a difficult exercise for a few reasons.
# There is very little research on pellicles when it comes to beer fermentation, so saying anything definitive about them is difficult, and identifying one or more microbes that created a pellicle is currently impossible.
# Numbers and size of bubbles in a pellicle is created by trapped CO2, and thus is not an identifying feature.
# The factors that cause pellicle formation are not well understood. Oxygen is said to cause pellicle formation, but how, why, and in what species is not known. Does more oxygen create a thicker pellicle? If so, for what species does this apply to? Does beer composition (more or less protein content, residual sugars, etc.) affect pellicle appearance? The lack of answers to these questions and others imply that environmental factors are also not helpful in identifying what species of microbe produced a pellicle.
# Identification of microbe species and sometimes even genus under a microscope based on cell morphology alone is not enough to be certain of that identification (see [http://suigenerisbrewing.blogspot.com/2014/12/brett-trois-riddle-wrapped-in-mystery.html this article on Trois identification] as an example), let alone attempting to identify microbes based on a visual "macro-level" formation such as a pellicle.