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medium must be found that results in translatable
microbiota complexity in a controlled and interpretable
setting.
The 10th Federation for Laboratory Animal Science
Associations (FELASA) symposium in 2007 was the
first FELASA symposium at which this question was
raised in one talk.23 At the 2010 FELASA symposium,
there were five oral presentations on the impact of the
microbiota on laboratory rodents,24 and at the
FELASA symposium in 2013 this further increased.25
In the same period, there was a general transition in
bacteriology from applying cultivation as the method
for screening and characterization of microbes to the
application of sequence-based methods. These began
with polymerase chain reaction-based methods and
have evolved to targeted generic 16S sequencing to
fully metagenomic sequencing. This has brought microbiological characterization from being able to identify
15% to 20% of the members of a microbiota to being
able to describe close to 100%. Moreover, we are now
able to describe not only the microbial phylogeny but
also the full functional capacity of the microbiota.
During the last decade, the costs of these procedures
have declined from being unreachable for routine purposes to being very amenable to routine use.
The emergence of next-generation sequencing tools
has led to a change in terminology and our understanding of microbiota. Previously, we might vaguely
describe normal flora, but this can now be referred to
as microbiota, which describes the complex community
of all microorganisms in the sample. With metagenomics we also now have a better understanding of
the microbiome, the massive collection of functional
genes. The latter represent more than one million
genes expressed by microbiota that far outweigh the
approximately 23,000 genes expressed by the mammalian host. This growing characterization and understanding of the complex microbiota has also led to a
new paradigm in which in addition to considering genetics as a basis for phenotype we must also consider the
influence of differing microbiota on said phenotypes.26
It is still premature to say where this development
will take us. Perhaps we will begin to routinely survey
the microbiome of our research subjects and even provide certificates akin to health certificates. Perhaps animals with specified microbiotas will be requested. It is
also likely that, like inbred strains, not all microbiotas
will be equally beneficial for all studies. If so, perhaps
producers will offer to supply the same strain with different microbiotas. Routine microbiota characterization would also benefit individual studies so
interindividual variation could be considered in
sample size calculations. Regardless, we have an obligation to incorporate anything that can improve science and animal welfare. The editors hope this special

Laboratory Animals 53(3)
issue of Laboratory Animals will provide the reader
contemporary information about this exciting field,
where it has taken animal research today, and where
it may go in the future.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with
respect to the research, authorship, and/or publication of this
article.

Funding
The author(s) received no financial support for the research,
authorship, and/or publication of this article.

ORCID iD
Axel Kornerup Hansen
2507

http://orcid.org/0000-0003-1575-

References
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AK and Nielsen DS (eds) Handbook of laboratory animal
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2015.
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https://orcid.org/0000-0003-1575-2507 https://orcid.org/0000-0003-1575-2507

Laboratory Animals - June Issue

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

Contents
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