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I decided to dedicate my thesis to the subject of the isolation of lactobacilli and other lactic acid-related bacteria (LARB) from the mucosae of the stomachs and jejuna of healthy
domestic pigs, as the interactions of these indigenous microorganisms and microhabitats are
utterly relevant for host animal nutrition and health.
In a first approach, I applied Lactobacillus-hydrogen peroxide (LHP), a newly developed
culture medium for the one-step direct specific isolation and qualitative analysis of hydrogen peroxide accumulation of lactobacilli. In combination with a screening catalase-benzidine dihydrochloride test, LHP constitutes a simple approach for the detection of manganese catalase-positive isolates of potentially novel Lactobacillus species. The new medium was validated as highly specific and limitedly sensitive for lactobacilli. The application of LHP facilitated the hitherto unreported detection of a haem-independent manganese catalase in the type strain of Lactobacillus plantarum subsp. plantarum. However, a colony isolate with an active catalase was not detected, and hence this first approach resulted in no promisingly novel Lactobacillus strain.
In a second approach, I used commercial mucin from porcine stomach as basal component of
two newly created culture media for the specific isolation of mucosa-associated LARB. The
isolated community comprised all three groups of LARB of the Firmicutes and Actinobacteria, namely the lactic acid-producing bacteria sensu stricto and sensu lato plus the metabolically linked lactic acid-fermenting bacteria. A 16S rRNA gene sequence-based phylogenetic analysis indicated that five of the total 27 isolates belonged to three novel species. I undertook polyphasic taxonomic analyses of four isolates and described Olsenella umbonata and Veillonella magna, a novel lactic acid-producing and -fermenting species, respectively, with now validly published name. These species were phenotypically characterised as being well adapted and, as other olsenellae and veillonellae, presumably indigenous to the gastrointestinal tract of pigs and other homeothermic vertebrates.