of pharmacologically active components of exotic foods, as well as reducing the
diversity of microbial intake, and the supply of data to the immune system?
18.4.9 Horizontal Gene Transfer
In addition to microbial molecular signals, and colonising organisms, the natural
environment can provide microbial genes (Hehemann et al. 2010; Smillie et al.
2011). For example, enzymes acquired by horizontal gene transfer (HGT) from
marine seaweed-associated bacteria enable the gut microbiota of Japanese individuals to metabolise seaweed carbohydrates (Hehemann et al. 2010). The frequency of
genes in the human microbiome that appear to have been acquired by HGT is
remarkably high (Liu et al. 2012; Yaffe and Relman 2019), and transfer can occur
between species that diverged in evolution millions of years ago. The natural
environment thus constitutes a resource of genetic diversity for the microbiota and
facilitates adaptation to a changing diet (Forsberg et al. 2012; Smillie et al. 2011).
The process of HGT must also help organisms from the natural environment to adapt
quickly to the gut (Fig. 18.2), so such environment-derived gut strains might rapidly
appear to differ from the environmental precursor (Sousa et al. 2017).
18.4.10 A Microbiota of high Biodiversity. . .Why Is It
Beneficial?
Contact with the natural environment is likely to increase the biodiversity of the
microbiota, and there is a strong correlation between this biodiversity and health.
Most illnesses are accompanied by reduced biodiversity of the microbiota, and a
progressive reduction in biodiversity heralds decline in the elderly (Claesson et al.
2012). Why is this so? Diversity is certainly important for providing data to the
immune system as described above. But it is also possible that it is not only the
diversity per se that is important, but also the increased likelihood of the presence of
essential species driving, for example, immunoregulation (Narushima et al. 2014;
Cekanaviciute et al. 2018) or production of short-chain fatty acids (Dalile et al.
2019), or other necessary functions not yet discovered. Compared to Italian children,
African children from villages in Burkina Faso had higher levels of SCFA (shortchain fatty acids), and their microbiota showed more species richness and biodiversity (De Filippo et al. 2010). Perhaps such richness and diversity reduce the
probability of loss of essential functions of the symbiotic microbial community
during periods of stress, dietary change, or antibiotic use? Ecologists have observed
that species diversity buffers against excessive change-induced damage to environmental ecosystems, because the presence of many species increases the probability
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G. A. W. Rook
diversity of microbial intake, and the supply of data to the immune system?
18.4.9 Horizontal Gene Transfer
In addition to microbial molecular signals, and colonising organisms, the natural
environment can provide microbial genes (Hehemann et al. 2010; Smillie et al.
2011). For example, enzymes acquired by horizontal gene transfer (HGT) from
marine seaweed-associated bacteria enable the gut microbiota of Japanese individuals to metabolise seaweed carbohydrates (Hehemann et al. 2010). The frequency of
genes in the human microbiome that appear to have been acquired by HGT is
remarkably high (Liu et al. 2012; Yaffe and Relman 2019), and transfer can occur
between species that diverged in evolution millions of years ago. The natural
environment thus constitutes a resource of genetic diversity for the microbiota and
facilitates adaptation to a changing diet (Forsberg et al. 2012; Smillie et al. 2011).
The process of HGT must also help organisms from the natural environment to adapt
quickly to the gut (Fig. 18.2), so such environment-derived gut strains might rapidly
appear to differ from the environmental precursor (Sousa et al. 2017).
18.4.10 A Microbiota of high Biodiversity. . .Why Is It
Beneficial?
Contact with the natural environment is likely to increase the biodiversity of the
microbiota, and there is a strong correlation between this biodiversity and health.
Most illnesses are accompanied by reduced biodiversity of the microbiota, and a
progressive reduction in biodiversity heralds decline in the elderly (Claesson et al.
2012). Why is this so? Diversity is certainly important for providing data to the
immune system as described above. But it is also possible that it is not only the
diversity per se that is important, but also the increased likelihood of the presence of
essential species driving, for example, immunoregulation (Narushima et al. 2014;
Cekanaviciute et al. 2018) or production of short-chain fatty acids (Dalile et al.
2019), or other necessary functions not yet discovered. Compared to Italian children,
African children from villages in Burkina Faso had higher levels of SCFA (shortchain fatty acids), and their microbiota showed more species richness and biodiversity (De Filippo et al. 2010). Perhaps such richness and diversity reduce the
probability of loss of essential functions of the symbiotic microbial community
during periods of stress, dietary change, or antibiotic use? Ecologists have observed
that species diversity buffers against excessive change-induced damage to environmental ecosystems, because the presence of many species increases the probability
348
G. A. W. Rook