Treg in an in vitro system, whereas spore forming organisms from MS patients failed
to do so, and even opposed this property of organisms from normal donors
(Cekanaviciute et al. 2018).
18.4.7 Spore-Forming Organisms as Probiotics
Other spore-forming organisms from the environment might also be important
despite not being prominent components of the human microbiota, and despite
mediating imperfectly understood functions, not all of which involve immunoregulation. Spores in soil have tended to be studied by environmental microbiologists and
ecologists, and the soil has been regarded as the natural habitat of the spore-forming
organisms such as Bacillus spp., despite awareness of the fact that many of them can
germinate and replicate in the intestinal tracts of insects and other animals (Nicholson 2002). Recently, it has been reported that spores of Bacillus subtilis can
germinate in the small bowels of mice and rabbits (Casula and Cutting 2002; Tam
et al. 2006). Moreover, after germination they replicated in the small bowel, and then
re-sporulated as they entered the colon. The same was observed in humans. Bacillus
subtilis strains were obtained from biopsies of human ileum and from faecal samples
(Hong et al. 2009a). There is therefore the possibility that B. subtilis and other
environmental spore-forming species should be regarded as gut commensals rather
than soil microorganisms (Hong et al. 2009b). B. subtilis is an important stimulus for
development of the gut-associated lymphoid tissue (GALT) in rabbits and sporulation of live bacilli within the GALT was considered critical to this process (Rhee
et al. 2004). We know little about the role of Bacillus spp. in humans, but bacillus
spores have been used as probiotics for many years (Casula and Cutting 2002; de
Castro et al. 2019). A recent study in Thailand noted that Staphylococcus aureus was
never found in the faecal or nasal microbiota of individuals whose faecal microbiota
included Bacillus species (Piewngam et al. 2018), and a preliminary study in the
Philippines suggested that treatment for a week with about 2 Â 10
9 spores of
Bacillus clausii strains accelerated the termination of acute childhood diarrhoea
(de Castro et al. 2019).
18.4.8 Strains That Adapt to Diet
Whether derived from the air or from soil, a subset of the organisms from the natural
environment can colonise the host, and supplement the microbiota (Fig. 18.2).
Indeed it has proved possible to reconstitute the gut microbiota of germ-free mice
using organisms from soil, though when caged with animals bearing a normal mouse
microbiota the mouse-gut-adapted strains rapidly replaced the soil-derived strains
(Seedorf et al. 2014). Many bacterial species such as Lactobacilli are found both in
soil and in the human gut but are these the same strains? The guess is that the answer
346
G. A. W. Rook
to do so, and even opposed this property of organisms from normal donors
(Cekanaviciute et al. 2018).
18.4.7 Spore-Forming Organisms as Probiotics
Other spore-forming organisms from the environment might also be important
despite not being prominent components of the human microbiota, and despite
mediating imperfectly understood functions, not all of which involve immunoregulation. Spores in soil have tended to be studied by environmental microbiologists and
ecologists, and the soil has been regarded as the natural habitat of the spore-forming
organisms such as Bacillus spp., despite awareness of the fact that many of them can
germinate and replicate in the intestinal tracts of insects and other animals (Nicholson 2002). Recently, it has been reported that spores of Bacillus subtilis can
germinate in the small bowels of mice and rabbits (Casula and Cutting 2002; Tam
et al. 2006). Moreover, after germination they replicated in the small bowel, and then
re-sporulated as they entered the colon. The same was observed in humans. Bacillus
subtilis strains were obtained from biopsies of human ileum and from faecal samples
(Hong et al. 2009a). There is therefore the possibility that B. subtilis and other
environmental spore-forming species should be regarded as gut commensals rather
than soil microorganisms (Hong et al. 2009b). B. subtilis is an important stimulus for
development of the gut-associated lymphoid tissue (GALT) in rabbits and sporulation of live bacilli within the GALT was considered critical to this process (Rhee
et al. 2004). We know little about the role of Bacillus spp. in humans, but bacillus
spores have been used as probiotics for many years (Casula and Cutting 2002; de
Castro et al. 2019). A recent study in Thailand noted that Staphylococcus aureus was
never found in the faecal or nasal microbiota of individuals whose faecal microbiota
included Bacillus species (Piewngam et al. 2018), and a preliminary study in the
Philippines suggested that treatment for a week with about 2 Â 10
9 spores of
Bacillus clausii strains accelerated the termination of acute childhood diarrhoea
(de Castro et al. 2019).
18.4.8 Strains That Adapt to Diet
Whether derived from the air or from soil, a subset of the organisms from the natural
environment can colonise the host, and supplement the microbiota (Fig. 18.2).
Indeed it has proved possible to reconstitute the gut microbiota of germ-free mice
using organisms from soil, though when caged with animals bearing a normal mouse
microbiota the mouse-gut-adapted strains rapidly replaced the soil-derived strains
(Seedorf et al. 2014). Many bacterial species such as Lactobacilli are found both in
soil and in the human gut but are these the same strains? The guess is that the answer
346
G. A. W. Rook