Laboratory Animals - June Issue - 237

Basic and Bleich

237

Figure 2. Application of the concept of gnotobiotic rodent husbandry.
The basic concept of gnotobiotic husbandry is to provide specific germ-free/gnotobiotic animal models for experimental
procedures or as a source of new pathogen-free animals. Germ-free animals are rederived from conventional or SPF
animals by hysterectomy or embryo transfer into the sterile environment of an isolator. Gnotobiotic rodent husbandry
represents isolated housing that is completely microbiologically segregated from the room environment. After rederivation, the core germ-free rodent breeding colony is established in an isolator where it can be maintained germ-free over
multiple generations. The progeny of this colony can be utilized in experiments or colonized with defined bacterial
consortia within the isolated system. Furthermore, gnotobiotic rodents can be returned to (conventional) barrier housing
where environmental microorganisms are present. For experimental setup, gnotobiotic animals can be transferred into
experimental isolators or short-term housing systems depending on the duration of the experiment.

Introduction of one or a few microorganisms at a
time provides valuable information on the causative
effect of a particular microbe on the model phenotype.
While this strategy might also be applied in conventional models, extraction of the molecular mechanism
is usually hindered in animals with complex microbiome. For example, in mouse models of inflammatory
bowel disease, association with Lactobacillus spp.35 or
Escherichia coli Nissle36 attenuated the disease, whereas
the introduction of Enterococcus faecalis,37 Bilophila
wadsworthia38 or Helicobacter hepaticus39 triggered colitis. Furthermore, murine norovirus (MNV) was also
shown to have microbe-dependent detrimental effects
on a susceptible host.40,41 However, MNV was also
shown to substitute for the beneficial influence of commensal bacteria in a non-susceptible host.42
Furthermore, E. coli Nissle was shown to promote
defects in the intestinal barrier mechanisms in the
absence of the CD14 gene.43
Associating mice with simplified microbial consortia
contributes to the standardization of the intestinal
microbiota and reduces interindividual variabilities
and the complexity of the microbiota. Furthermore,
mice associated with defined microorganisms can be
morphologically and functionally similar to mice associated with complex microbiota.10 A well-known

example of a defined bacterial microbiota consisting
of bacteria isolated from the murine gut was developed
by Russell W. Schaedler.44 This community was refined
and standardized by Roger P. Orcutt, resulting in the
generation of the 'Altered Schaedler Flora' (ASF), a
model community of eight bacterial species that was
mainly used by commercial rodent vendors.45,46
However, the ASF consortium is also widely used in
biomedical research. This model community can be utilized for a wide range of studies including microbiological, immunological and metabolic studies.46 As
the ASF community represents a normal murine gut
microbiota, this community can be used to gain knowledge about the gut ecology and spatial distribution of
commensal representatives.47 This model community
can also be used to assess perturbations in the enteric
microbiota upon infection with pathogens or colonization by other commensals.46,48 Furthermore, the ASF
community can be used to evaluate the organism-specific impact on the host immune system.49,50 Recently,
several novel human and mouse model communities
were developed. The 'Oligo Mouse Microbiota' is a
new model community composed of 12 bacterial species
isolated from mice that represent members of the major
bacterial phyla in the murine intestine. This microbiota
provides partial resistance to colonization by



Laboratory Animals - June Issue

Table of Contents for the Digital Edition of Laboratory Animals - June Issue

Contents
Laboratory Animals - June Issue - Cover1
Laboratory Animals - June Issue - Cover2
Laboratory Animals - June Issue - Contents
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