Blautia is a genus of anaerobic bacteria with probiotic characteristics that occur widely in the feces and intestines of mammals. Based on phenotypic and phylogenetic analyses, some species in the genera Clostridium and Ruminococcus have been reclassified as Blautia, so to date, there are 20 new species with valid published names in this genus. An extensive body of research has recently focused on the probiotic effects of this genus, such as biological transformation and its ability to regulate host health and alleviate metabolic syndrome. This article reviews the origin and biological characteristics of Blautia and the factors that affect its abundance and discusses its role in host health, thus laying a theoretical foundation for the development of new functional microorganisms with probiotic properties.
Fructooligosaccharides (FOS) are a well-known class of prebiotic and are considered to selectively stimulate the growth of bifidobacteria in the gut. Previous studies focused on the growth stimulation of Bifidobacterium, but they did not further investigate the bifidobacterial composition and the specific species that were stimulated. In this study, mice were fed with FOS in different doses for four weeks and the composition of fecal microbiota, in particular Bifidobacterium, was analyzed by sequencing the V3–V4 region and the groEL gene on the MiSeq platform, respectively. In the high-dose group, the relative abundance of Actinobacteria was significantly increased, which was mainly contributed by Bifidobacterium. At the genus level, the relative abundances of Blautia and Coprococcus were also significantly increased. Through the groEL sequencing, 14 species of Bifidobacterium were identified, among which B. pseudolongum was most abundant. After FOS treatment, B. pseudolongum became almost the sole bifidobacterial species (>95%). B. pseudolongum strains were isolated and demonstrated their ability to metabolize FOS by high performance liquid chromatography (HPLC). Therefore, we inferred that FOS significantly stimulated the growth of B. pseudolongum in mice. Further investigations are needed to reveal the mechanism of selectiveness between FOS and B. pseudolongum, which would aid our understanding of the basic principles between dietary carbohydrates and host health.
This
research assessed the anti-inflammatory and hepatoprotective
properties of inosine and the associated mechanism. Inosine pretreatment
significantly reduced the secretion of several inflammatory factors
and serum alanine transaminase (ALT) and aspartate amino transferase
(AST) levels in a dose-dependent manner compared with the lipopolysaccharide
(LPS) group. In LPS-treated mice, inosine pretreatment significantly
reduced the ALT and malondialdehyde (MDA) concentration and significantly
elevated the antioxidant enzyme activity. Furthermore, inosine pretreatment
significantly altered the relative abundance of the genera, Bifidobacterium, Lachnospiraceae UCG-006, and Muribaculum. Correlation
analysis showed that Bifidobacterium and Lachnospiraceae UCG-006 were
positively related to the cecal short-chain fatty acids but negatively
related to the serum IL-6 and hepatic AST and ALT levels. Notably,
inosine pretreatment significantly modulated the hepatic TLR4, MYD88,
NF-κB, iNOS, COX2, AMPK, Nfr2, and IκB-α expression.
These results suggested that inosine pretreatment alters the intestinal
microbiota structure and improves LPS-induced acute liver damage and
inflammation through modulating the TLR4/NF-κB signaling pathway.
Quorum
sensing (QS)-based dynamic regulation has been widely used
as basic tool for fine-tuning gene expression in response to cell
density changes without adding expensive inducers. However, most reported
QS systems primarily relied on down-regulation rather than up-regulation
of gene expression, significantly limiting its potential as a molecular
switch to control metabolic flux. To solve this challenge, we developed
a bifunctional and modular Phr60-Rap60-Spo0A QS system, based on two
native promoters, P
abrB
(down-regulation by Spo0A-P) and P
spoiiA
(up-regulation by Spo0A-P). We constructed
a library of promoters with different capacities to implement down-regulation
and up-regulation by changing the location, number, and sequences
of the binding sites for Spo0A-P. The QS system can dynamically balance
the relationship between efficient synthesis of the target product
and cell growth. Finally, we validated the usefulness of this strategy
by dynamic control of menaquinone-7 (MK-7) synthesis in Bacillus
subtilis 168, a model Gram-positive bacterium, with the bifunctional
Phr60-Rap60-Spo0A quorum sensing system. Our dynamic pathway regulation
led to a 40-fold improvement of MK-7 production from 9 to 360 mg/L
in shake flasks and 200 mg/L in 15-L bioreactor. Taken together, our
bilayer QS system has been successfully integrated with biocatalytic
functions to achieve dynamic pathway regulation in B. subtilis 168, which may be extended for use in other microbes to fine-tune
gene expression and improve metabolites production.
Constipation, which seriously affects living quality of people, is a common gastrointestinal disease. The engagement of the intestinal flora in the development of symptoms of constipation has been frequently hypothesized. In this study, constipated mice induced by loperamide were used to investige the alleviation of constipation by Bifidobacteria. Bifidobacteria was sorted out according to their adhesive properties into two groups. One group combined multiple strains of
Bifidobacterium
with adhesion property (CMB1), the other combined multiple strains of
Bifidobacterium
without adhesion property (CMB2). It was found that CMB1 can alleviate constipation more efficiently by improving the water, propionate and butyrate content in feces, and overall gastrointestinal transit time. Meanwhile, from the perspective of fecal microbiota, CMB1 alleviated constipation mainly by increasing the relative abundances of genera (
Bifidobacterium
,
Lactobacillus
, and
Prevotella
) associated with rapid bowel movement. From the perspective of cecal microbiota, CMB1 alleviated constipation mainly by increasing the relative abundances of genera
Lactobacillus
,
Bacteroides
, unclassified S24-7,
Dorea
,
Ruminococcus
,
Coprococcus
, and
Rikenella
, and decreasing the relative abundances of genera
Oscillospira
,
Odoribacter
and Unclassified F16, which are associated with methane production and colonic transit. Overall, changes of microbiota in caecum by CMB1 reflect the stage of constipation in mice more comprehensively than that in feces.
Fructooligosaccharides (FOS) are considered prebiotics and have been proven to selectively promote the growth of Bifidobacterium in the gut. This study aimed to clarify the effects of FOS intake on the composition of luminal and mucosal microbiota in mice. Briefly, mice were fed a 0% or 25% FOS (w/w)-supplemented diet for four weeks, and the composition of luminal and mucosal microbiota, especially the Bifidobacterium, was analyzed by sequencing the V3–V4 region of 16S rRNA and groEL gene, respectively. After FOS intervention, there were significant increases in the total and wall weights of the cecum and the amount of total short-chain fatty acids (SCFAs) in the cecal contents of the mice. At the phylum level, the results showed a significant increase in the relative abundance of Actinobacteria in the contents and mucosa from the cecum to the distal colon in the FOS group. Besides Bifidobacterium, a significant increase was observed in the relative abundance of Coprococcus in all samples at the genus level, which may be partially related to the increase in butyric acid levels in the luminal contents. Furthermore, groEL sequencing revealed that Bifidobacterium pseudolongum was almost the sole bifidobacterial species in the luminal contents (>98%) and mucosa (>89%). These results indicated that FOS can selectively promote B. pseudolongum proliferation in the intestine, either in the lumen or the mucosa from the cecum to the distal colon. Further studies are required to reveal the competitive advantage of B. pseudolongum over other FOS-metabolizing bacteria and the response mechanisms of B. pseudolongum to FOS.
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