I would preface this to say that what I state is based on observation from myself and others, I have learned that there are few absolutes.
Here are some general references posted below. The intestinal environment is very complex and diverse, pro-biotics play key roles in many functions especially combining with fiber to produce SCFA's etc.
I am not so convinced that indiscriminately supplementing with probiotics is necessarily a good idea much to the dismay of many promoters of probiotics. Dr. Leo Galland has talked about this on his website. He mentions the change in the immune expression by adding probiotics which could be a negative thing. Here is a link to his articles in which he addresses GI health in several different articles http://mdheal.org/articles.htm
There are a number of things that assist such as keeping healthy sIgA levels (colostrum, vitamin a & vitamin d3) along with adequate fiber (non-soluble), healthy organic foods, adequate oxygen levels in the gut, etc.
I think the wise thing to do is if you try the probiotics to assess your situation and not necessarily use them all the time. I am on a number of anti-biotic type of things and find it necessary to supplement with probiotics from time to time.
"Protozoa are tiny single-celled animals that mainly feed on bacteria (think of them as little grazers), although some eat other protozoa and organic matter."
Preferential Feeding by the Ciliates Chilodonella and Tetrahymena spp.
and Effects of These Protozoa on Bacterial Biofilm
Structure and Composition
Andrew Dopheide,1 Gavin Lear,1† Rebecca Stott,2 and Gillian Lewis1*
School of Biological Sciences, University of Auckland, 3a Symonds Street, Auckland, New Zealand,1 and National Institute for
Water and Atmospheric Research, P.O. Box 11-115, Hamilton, New Zealand2
Received 12 October 2010/Accepted 9 May 2011
Protozoa are important components of microbial food webs, but protozoan feeding preferences and their
effects in the context of bacterial biofilms are not well understood. The feeding interactions of two contrasting
ciliates, the free-swimming filter feeder Tetrahymena sp. and the surface-associated predator Chilodonella sp.,
were investigated using biofilm-forming bacteria genetically modified to express fluorescent proteins. According
to microscopy, both ciliates readily consumed cells from both Pseudomonas costantinii and Serratia plymuthica
biofilms. When offered a choice between spatially separated biofilms, each ciliate showed a preference
for P. costantinii biofilms