Really, this is a no brainer, but it's great that it's finally been "verified". Of course fibre boosts beneficial gut flora! In a healthy gut, that's all that there is for them to eat. All of the useful carbohydrates, proteins and lipids, etc., should have been digested and absorbed. Unfortunately, due to general trends in diet and lifestyle these days, almost everyone's digestion is compromised to some degree. That leads to alterations in gut flora, which is one of the primary causes of the development of inflammatory diseases of the digestive tract. It's sad (but typical) that for decades the medical establishment claimed that probiotics were useless. Another kind of snake oil promoted by natural health practitioners. However, in the last decade they have become the rage, at least among researchers. Their use hasn't percolated down to the doctors and nurses in the front lines to any great degree yet. There's been tons of research on their health promoting benefits, from improving digestion to boosting the immune system. Of course no one admitted they were wrong, but at least this the information is finally getting out there to the general public.
The moral of the story is that for this and many other reasons it's important to eat lots of fibre. In situations where taking probiotics is recommended, take them with some source of (preferably soluble) fibre. I personally recommend taking them with whole flax seeds and/or psyllium husks - certified organic of course!
Many people who take probiotic supplements may have heard of fructooligosaccharides (FOS). These are relatively small polysaccharides composed of fructose units. They are particularly common in the latex and roots of herbs from the Aster family like elecampane (Inula helenium), dandelion (Taraxacum officinale), chicory (Cichorium intybus) and burdock (Arctium spp.). They are undigestible by humans and therefore make up part of the fibre content of our diet. They are one of the kinds of fibre that help promote healthy intestinal flora. Many probiotic supplements include FOS and often charge more money for it. Be forewarned that this is just a gimmick. The amount of FOS in these products is irrelevant. That doesn't mean that some of them aren't good quality products. But their inclusion of FOS is for optics only. It adds virtually no value to the product. If you want FOS, eat Jerusalem artichokes (Helianthus tuberosus) or very young dandelion, burdock or chicory roots (the roots of older plants may make great medicine, but not great eating). When it comes to probiotics, take them with soluble fibre and you'll get much better results.
Elecampane (Inula helenium).