Are the intestinal microbiota substantially different within a diverticulum of the colon?
The appendix is a type of true diverticulum of the colon, although it is one that is present in everyone (unless a surgeon has removed it). There are bacteria in the gut from the mouth all the way down to the anus, and the numbers and types of bacteria change along the length of the intestinal tract. A recent review from J. Ridlon published in the Journal of Lipid Research (2006) is available online and has documented these observations from a number of investigators. In that paper the bacterial species are described as changing as well as the relative abundances of bacteria which increases along the length of the intestinal tract. Figure 1 from that paper which is open access available from the link above is below.



I think its interesting that the wiki page you're citing states that individuals without an appendix were more likely to develop a recurrent C. diff infection. One could interpret that as they did on that site that somehow the appendix is repopulating the colon and making that individual more resistant to a repeat or "Recurrent" infection. However, I don't know of any studies that have directly tested that hypothesis.

In terms of whether or not the gut flora - aka "gut microbiota" - are significantly different in the appendix is possible, but I don't think anyone has identified that just yet. One of the problems with this would be that we don't routinely remove appendices unless they are infected/inflamed which intrinsically would alter the microbiome locally.

So, is it possible that the microbiome could be significantly different in the appendix itself compared to the cecum just a few centimeters away? The answer would be - potentially, but no one has been able to address that question to date.