a) None of them that I've ever spoken to or met, online or otherwise. Creationists are a huge collection of people, and though some of them may be educated in such matters, the vast majority are basically "anti-evolutionists" too. This is the problem when you lump people into only a handful of categories, and those people still REFER to themselves as those categories (i.e. I'm a mathematician, but it doesn't mean I agree with other mathematicians as regards the utility of IT, for instance).
b) Species has a definition, which basically involves whether they can successfully interbreed again. In this case, you would expect one species to be distinctly different to any other, and for them to "compete" for resources such that they aren't compatible (i.e. one does not co-exist in the presence of the other). It's much deeper and more complicated than that, and there is a certain borderline of interpretation, but things having distinctly different digestion habits is highly indicative of new STRAINS (i.e. species at this level). It'd be like a human suddenly gaining the ability to breathe carbon dioxide, and giving birth to others with the same ability. Not just "oh, that's odd, you're allergic to bread", but an entirely new way of surviving that other strains can NEVER do.
c) It's poorly summarised, maybe, but "This citrate could be a second food source for the bacteria, but one of the defining characteristics of E. coli as a species is its inability to grow on citrate when oxygen is present." - as such it's able to "grow using entirely new food sources" (citrate - oxygen instead of citrate + oxygen).