on zinc nutrition and the microbiota
Increased dietary zinc oxide changes the bacterial core and enterobacterial composition in the ileum of pigletshttp://animalsci.highwire.org/content/89/8/2430.full
"This study was conducted to investigate the effects of increased dietary ZnO on the bacterial core and enterobacterial composition in the small intestine of piglets that were fed diets containing a total of 124 or 3,042 mg of Zn per kilogram of diet, respectively. ... Increased dietary ZnO led to an increase of less prominent species and, thus, had a major impact on the bacterial composition and diversity in piglets. This effect may help to stabilize the intestinal microbiota in the sensitive postweaning period. ... The dominating L. reuteri was influenced by greater ZnO supplementation, whereas the second most dominant L. amylovorus was not affected. Other lactobacilli, like L. salivarius, L. johnsonii, or L. helveticus, seemed to trade places in rank. The species specific response to ZnO supplementation may indicate different tolerance mechanisms against greater Zn inclusion; however, it could also be a result of interspecies competition. Considering the drastic increase in abundance of Weissella spp. and Leuconostoc spp., bacteriocin production may also have played a role. Like many other LAB, both genera are known to produce bacteriocins active against other LAB (Papathanasopoulos et al., 1997; Srionnual et al., 2007).
Sequences of the Clostridiales order in the bacterial core mainly consisted of Sarcina ventriculi, an acid-tolerant strict anaerobic species, found in the intestinal tract of piglets and other mammals (Crowther, 1971; Vatn et al., 2000; Thanantong et al., 2006). This species seemed to be very sensitive against ZnO or indirect modifications induced by increased dietary ZnO. The fact that S. ventriculi has also been found in the stomach of horses (Husted et al., 2010), lambs, dogs (Vatn et al., 2000), and free-living Colobus monkeys (Owaki et al., 1974), together with its ability to grow at low pH, indicates that this species may be autochthonous to the stomach of mammals.
An interesting result was observed for Enterobacteriaceae. Although not statistically significant, most detected species increased numerically in relative abundance because of increased dietary ZnO. It should be mentioned that sequence data were generated from a PCR using the same concentration of target DNA, and thus, some species with low relative abundance may have fallen below the detection limit because of the high abundance of a few dominant members. Nevertheless, enterobacteria seemingly gained colonization potential by increased dietary ZnO; substantially more enterobacterial species were detected in animals from the high dietary ZnO trial group. This is in agreement with a previous study by Højberg et al. (2005). Furthermore, a survey of Canadian pig farms revealed an increased presence of an enteropathogenic E. coli strain in farms using dietary greater dietary ZnO (Amezcua et al., 2008). Also, an increase in enterobacterial diversity was observed in a study with piglets (Katouli et al., 1999). These results indicate that dietary ZnO causes an enhanced colonization with enterobacteria in the small intestine of piglets. Consequently, the frequently observed diarrhea-reducing effect of ZnO may not be related to direct reducing effects on pathogenic E. coli, but rather to an increase of the enterobacterial group, which would increase competition among enterobacteria."
there.s LOADS of info here on zinc and 'leaky gut' aka intestinal permeability. examples:chronic-cerebrospinal-venous-insufficiency-ccsvi-f40/topic17642-15.html#p174244general-discussion-f1/topic6906.html#p54065
general search results on zinc + tight + junctionssearch.php?keywords=%2Btight+%2Bjunction+%2Bzinc&terms=all&author=jimmylegs&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Searchchronic-cerebrospinal-venous-insufficiency-ccsvi-f40/topic17642-15.html#p174244