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very significant effect that the gut microbiota can have
on the host immune response.15
In summary, these studies show that the microbiota
of wild and laboratory animals differ, and also suggest
that the gut microbiota changes as animals move from
the wild to the laboratory, though the dynamics of this
process needs to be explored further.

Gut microbiota of other wild rodents
The gut microbiota of other wild rodents has also been
studied. A two-year, longitudinal study of wood mice,
Apodemus sylvaticus, showed marked seasonal changes
in the composition of the gut microbiota, hypothesised
to be driven by seasonal changes in the animals' diet.16
Work with A. flavicollis sought relationships between
the gut microbiota and macroparasite infection, finding
no such effect on microbiota diversity, but significant
effects on the composition on the microbiota and on the
abundance of specific bacterial taxa.17
Analysis of the gut microbiota of two species of
Peromyscus spp. showed no significant differences in
the species' microbiota, though there was substantial
inter-individual variation in the microbial communities.18 The gut microbiota of wild naked mole-rats,
Heterocephalus glaber, has also been described and
found to be distinct from those of a range of other
mammals.19

Gut microbiota effects on an animals'
biology
Studies of laboratory animals have shown that the
microbiota has multiple, important effects on animals'
development, immune responses, acquisition of nutrition from food, behaviour, and other physiological processes. Analogous effects are likely to occur in wild
animals, such that multiple aspects of the lives of wild
animals will be affected by their microbiota.20 To date,
this has hardly been examined in wild animals, but
obviously it is a priority to do so.
One important role of the microbiota can be to
detoxify components of an animal's diet.20 This has
been studied in wild woodrats, where dietary toxins
commonly present in their diet can increase the diversity of the microbiota (and so detoxify the toxins),
whereas novel toxins depress the microbiota diversity.21
The oxalate-rich diet of wild woodrats, Neotoma albigula, appears to be important in driving the presence of
potentially oxalate-degrading bacteria in its gut,22,23
consistent with other studies showing how an animal's
diet can finely-tune the composition of its microbiota.24
The important insight from these studies is showing
that hosts have an evolved association with their microbiota and that it contributes to host fitness.21,25,26

Laboratory Animals 53(3)
Studies in bank voles, Myodes glareolus, also show
this. Lines selected for maintaining body mass when
fed a high-fibre diet had an altered gut microbiota community structure (compared with control lines), with the
caecal microbiota being comparatively more diverse.27

Outstanding questions about the gut
microbiota
Despite the relatively few studies of wild rodents, the
picture that is emerging is that in these populations
there are significant inter-individual differences in the
gut microbiota. This is, perhaps, not surprising, but it is
important, especially since this is something that is not
captured in studies of laboratory animals. Indeed, one
of the underlying rationales of using laboratory animals
is to minimise differences among individual animals.
Key questions pertaining to these inter-individual differences in gut microbial diversity in wild animals are
what causes this (for example, the relative importance
of genetic and environmental effects and their interaction), what are the dynamics of this, and what are
the consequences of this both for the constituent taxa
of the microbiota but also for the host itself? As has
been elegantly shown, the gut microbiota has a major
effect on the host immune response.15 By extension,
differences among individual wild animals in their
microbiota would be predicted to drive immuneheterogeneity among wild animals.3 This will also feedback since the differing immune state of animals will
itself affect components of the microbiota.15 A major
focus of laboratory animal studies is the immune
system. That the gut microbiota can change an animals'
immune response to an infection (changing an animal
from being fully susceptible to fully resistant to
viral infection)15 requires a major re-evaluation of the
utility of immunological studies in model laboratory
animals. If laboratory mice are being used as a broadview model of mammals (model, sense 1, above)
then these models would continue to have some validity. However, if they are being used as models of freeliving animals, be those human or non-human (model,
senses 2 and 3, above), then the models' validity and
utility must be severely compromised.

Gut microbiota research opportunities with
wild animals
There are several major themes of gut microbiota
research that have been pursued using laboratory animals, including the study of the immunological interface
between the microbiota and its host, the processes that
assemble and maintain the microbiota community composition, and the functional effect (particularly nutritional) of the microbiota. These have yet to be



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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