The term is "peptiDOglycan" NOT "peptiDIOglycan". Granted, I am not your target demographic, as I am a college graduate with a degree in microbiology, but you might consider teaching the correct terms to your high school students. Presenting mistakes like this might not matter to a student learning this information for the first time, but it SERIOUSLY hurts your credibility when you cannot pronounce or spell the utmost basic terminology for the subject.

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@ James843 and everyone else: Peptidoglycan (spelled p-e-p-t-i-d-o-g-l-y-c-a-n) is indeed found in both Gram-positive and Gram-negative bacteria. Gram-positive bacteria, like B. subtilis, have a thick layer of peptidoglycan. In contrast, Gram-negative bacteria, like E. coli, possess a thin layer of peptidoglycan surrounded by an outer membrane. There is no such thing as p-e-p-t-i-d-i-o-g-l-y-c-a-n. The information in the video is still incorrect. I highly doubt that the 8th edition of Campbell and Reece would be published with the term mispelled, since the 3rd, 5th, 6th, and 7th editions all spell the term correctly and their new editions do not vary that much. However, I do not have access to the AP 8th edition of the text, so it might be a possibility. Stranger things have happened. Regardless, the term is indeed spelled p-e-p-t-i-d-o-g-l-y-c-a-n without the extra I between the D and O.   References:   Journal Publication: "Peptidoglycan Types of Bacterial Cell Walls and their Taxonomic Implications" by Schleifer & Kandler - Published in 1972 Link to the Full Article: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC408328/pdf/bactrev00201-0002.pdf   Biology by Campbell and Reece: 3th Edition - page 517 (ISBN: 0-8053-1880-1) 5th Edition - page 504 (ISBN: 0-8053-6573-7) 6th Edition - page 528 (ISBN: 0-8053-6624-5) 7th Edition - page 535 (ISBN: 0-8053-7171-0)   Lab Manual Companion for the 7th Edition of Biology by Campbell and Reece: Investigating Biology Lab Manual 5th Edition Annotated Instructor's Edition by Morgan & Carter -page 334 (ISBN: 0-8053-7180-X)   Other Science Textbooks: Biology 5th Edition by Solomon, Berg, & Martin - page 491 (ISBN: 0-03-022299-0) Textbook of Diagnostic Microbiology 3rd Edition by Mahon, Lehman & Manuselis - page 11 (ISBN: 1-4160-2581-2) Principles of Biochemistry 5th Edition by Nelson & Cox - page 796 (ISBN: 0-7167-7108-X)