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Page 2 of 12 Horie et al. Microbiome Res Rep 2024;3:35 https://dx.doi.org/10.20517/mrr.2024.08

feeding habits of host animals; at the phylum level, Bacillota was predominant in all animals; on the other hand,
herbivores tended to have a higher proportion of Bacteroidota than carnivores, and piscivores tended to have a
higher proportion of Proteobacteria.

Conclusion: Lactic acid bacteria differ among animal species in a manner dependent on the hosts’ feeding habits.

Keywords: Lactobacillaceae, intestinal flora, carnivores, herbivores, piscivores

INTRODUCTION
Probiotics are defined as “live microbial feed supplement which beneficially affects the host animal by
[1]
improving its intestinal balance”, a concept proposed by Fuller in 1989 . Another definition, “mono- or
mixed cultures of live microorganisms which, when applied to animal or man, beneficially affect the host by
improving the properties of the indigenous microflora”, was also proposed by Havenaar and Huis in’t
Veld , and Holzapfel et al. . The Food and Agriculture Organization/the World Health Organization
[2]
[3]
(FAO/WHO) also defined probiotics as “live microorganisms which, when administered in adequate
amounts, confer a health benefit on the host” [4] .

Common beneficial effects of probiotics on the host include preventing diarrheal diseases , stimulating
[5-8]
[13]
the immune system [9,10] , anti-inflammatory effects [11,12] , and inhibiting the growth of pathogenic bacteria .
Other potential benefits of probiotics include regulating blood cholesterol levels, uric acid metabolism ,
[14]
promoting skin wound healing , reducing abdominal visceral fat and total fat levels , and improving liver
[16]
[15]
function . Probiotics also affect the intestinal flora. In pigs treated with Clostridium butyricum MIYAIRI
[17]
588 (CBM588), higher levels of Lactobacillaceae at the family level, Bifidobacterium at the order level, and
Lactobacillus ruminis and Bifidobacterium pseudolongum at the species level were observed compared to the
[18]
non-treated group .
The potential of probiotics depends more on the strain than the bacterial species itself. Specific biological
activities beneficial to the host are associated with particular bacterial strains. The most important bacteria
reported as probiotics are lactic acid bacteria. Limosilactobacillus reuteri (L. reuteri), as a probiotic, is known
to have some beneficial properties to host. L. reuteri CRL 1098 reduced blood cholesterol . L. reuteri ML1
[19]
[20]
stimulated the immune system . Another L. reuteri strain eliminated pathogenic microorganisms and
fungi by secreting the bacteriocin reuterin .
[21]
[13]
Limosilactobacillus fermentum can inhibit the growth of Candida glabrata by depleting ergosterol .
Ingestion of Lacticaseibacillus casei (L. casei) strain Shirota, also known as Yakult, reduced antibiotic-
associated diarrhea . Lactobacillus gasseri SHMB 0001 derived from human milk showed a protective effect
[5]
against DSS-induced mice colitis via enforcing gut barrier, downregulating pro-inflammatory cytokines,
and modulating gut microbiota . Lactic acid bacteria as probiotics exhibit immunostimulatory activity and
[22]
[23]
anti-inflammatory responses through crosstalk with host intestinal epithelium . The benefits of probiotics
have been observed not only in humans but also in other animals like mammals and birds, particularly in
laboratory and domestic animals. For instance, lambs given a mixture of L. casei HM-09 and
Lactiplantibacillus plantarum HM-10 experienced decreased visceral fat accumulation and increased
unsaturated fatty acids in muscle while saturated fatty acids decreased . Chickens fed Lacticaseibacillus
[24]
chiayiensis AACE3 showed higher body weight gain and digestive enzyme activity, along with lower levels
of pro-inflammatory cytokines compared to those not given the probiotic .
[25]