We advise that you perform a search in the library catalogue using the terminology Escherichia coli, first in Subject, then if all items are checked out - in Anywhere. Again, if all items are in use – broaden the search. Try to be less specific: a Subject search of Microbiology (for e-coli) or a Subject search of Molecular Biology (for x-gal testing). Use the index of the book(s) to find your terms. We found x-gal testing and e-coli bacterium information in Basic Methods in Molecular Biology by Davis.