O‐acetylesterase activity of Bifidobacterium bifidum sialidase facilities the liberation of sialic acid and encourages the proliferation of sialic acid scavenging Bifidobacterium breve

Abstract

Bifidobacterium bifidum possesses two extracellular sialidases (SiaBb1 and SiaBb2) that release free sialic acid from mucin sialoglycans, which can be utilized via cross-feeding by Bifidobacterium breve that, otherwise, is prevented from utilizing this nutrient source. Modification of sialic acids with O-acetyl esters is known to protect mucin glycans from degradation by bacterial sialidases. Compared to SiaBb2, SiaBb1 has an additional O-acetylesterase (Est) domain. We aimed to elucidate the role of the SiaBb1 Est domain from B. bifidum in sialic acid crossfeeding within Bifidobacterium. Pre-treatment of mucin secreted from bovine submaxillary glands (BSM) using His 6 -tagged-Est and -SiaBb2 released a higher amount of sialic acid compared to the pretreatment by His 6 -SiaBb2. Growth of B. breve increased with an increase in nanE expression when supplemented with both His 6 -Est-and His 6 -SiaBb2-treated BSM. These results indicate that the esterase activity of the SiaBb1 Est domain enhances the efficiency of SiaBb2 to cleave sialic acid from mucin. This free sialic acid can be utilized by coexisting sialic acid scavenging B. breve via crossfeeding. Here, we provide the molecular mechanism underlying the unique sialoglycan degradation property of B. bifidum which is mediated by the complementary activities of SiaBb1 and SiaBb2 in the context of sialic acid cross-feeding.

Cross-feeding of bifidobacteria promotes intestinal homeostasis: a lifelong perspective on the host health

“…bifidum releases more lactose by upregulating the gene expression of the enzymes and transporters involved 98 . A similar phenomenon was observed in the co-culture of mucin and sialylated glycan 59 , 99 . Chen et al 100 demonstrated that B .…”

“…The genome of B . breve mostly contains genes involved in the breakdown of lactose, fucose, sialic acid, and amino sulfate 59 – 61 . Specifically, the external sialidase (GH33) in B .…”

Gut Microbial Sialidases and Their Role in the Metabolism of Human Milk Sialylated Glycans

“…The modification of SAs with O -acetyl esters prevents the hydrolysis of mucin O -glycans by bacterial sialidases. It has been demonstrated that the esterase activity of the SiaBb1 O -acetylesterase domain increases the efficiency of SiaBb2 to remove SA from mucin [ 73 ]. Unlike B. bifidum sialidases, the two cloned B. infantis sialidases are located intracellularly and release α-2,3- and α-2,6-linked sialosides, with preference for α-2,6-glycosyl linkage [ 46 ].…”

Construction of Probiotic Double-Layered Multinucleated Microcapsules Based on Sulfhydryl-Modified Carboxymethyl Cellulose Sodium for Increased Intestinal Adhesion of Probiotics and Therapy for Intestinal Inflammation Induced by Escherichia coli O157:H7

“…Bifidobacterium is one of the most widely studied probiotics, which can positively regulate the intestinal microbiota and effectively inhibit enteritis. − On this basis, to ensure the adhesion of probiotics in the microcapsules to the intestine upon release and specifically promote the growth of probiotics rather than pathogenic bacteria, Bifidobacterium extracellular sialidase is used which can enhance the adhesion of probiotics to mucosa and support carbohydrate assimilation. , Bifidobacterium has a positive tolerance to digestive tract conditions, adhesive ability to intestinal epithelial cells, regulatory effect on immune cell activity, regulation of intestinal microbiota, and restoration of the intestinal barrier. , However, the mechanism of improving the symptoms of bacterial enteritis by regulating the intestinal microbiota has not been clarified. In addition, when Bifidobacterium interferes with intestinal microecology as a probiotic, its effective amount and intestinal adhesion play an important role in giving full play to its probiotic characteristics.…”

“…The adhesion of probiotics is mainly based on the nonspecific interaction between two surfaces and the specific interaction between the mucus layer (protein) and the receptor . At the same time, studies have found that intestinal mucus also contains many cysteines, which also exist in the outer membrane of bacteria or the protein layer on the cell surface. , When compounds with sulfhydryl groups are in contact with mucus (glycoprotein), they form strong covalent bonds (S–S disulfide bonds), which ensure the positioning of the probiotic delivery system at the target point, thus enhancing the intestinal adhesion of probiotics . Therefore, thiolation treatment can also be used as one of the methods to prolong the adhesion time of probiotics in the intestine.…”