Probiotic profiling of bifidobacteria indigenous to the human intestinal mucosa shows alleviation of dysbiosis-associated pathogen biofilms

The present study was undertaken to isolate bifidobacterial probiotics and characterize the biodiversity of mucosal bacteria in the human distal gut through 16S rRNA amplicon sequencing. Bifidobacterial strains obtained by selective culturing were investigated for biofilms and probiotic characteristics. Both culture-dependent and culture-independent approaches revealed substantial microbial diversity. Bifidobacterium strains yielded robust biofilms with predominantly exopolysaccharides and eDNA matrix. Microscopy revealed species-dependent spatial arrangement of microcolonies. Following probiotic profiling and safety assessment, the inter- and intra-specific interactions in in dual strain bifidobacterial biofilms were studied. As a species, only strains of B. bifidum exhibited exclusively inductive type of interactions whereas in other species, the interactions were more varied. On the other hand, in dual species biofilms, a preponderance of inductive interactions was evident between B. adolescentis, B. thermophilum, B. bifidum, and B. longum. The strong biofilm-formers also diminished pathogenic biofilm viability, and some were proficient in cholesterol removal in vitro. None of the strains exhibited harmful enzymatic activities associated with disease pathology. Interaction between biofilm-forming bifidobacterial strains provides an understanding of their functionality and persistence in the human host, and food or medicine. Their anti-pathogenic activity represents a therapeutic strategy against drug-resistant pathogenic biofilms.

Automated summary

The present study aimed to isolate bifidobacterial probiotics and characterize the diversity of mucosal bacteria in the human distal gut using 16S rRNA amplicon sequencing. The obtained bifidobacterial strains were analyzed for biofilms and probiotic properties. Both culture-dependent and culture-independent methods revealed a significant microbial diversity. Bifidobacterium strains formed strong biofilms primarily composed of exopolysaccharides and eDNA matrix. Interactions between different strains varied, with B. bifidum showing exclusively inductive interactions. Additionally, dual species biofilms displayed a predominance of inductive interactions between B. adolescentis, B. thermophilum, B. bifidum, and B. longum. Strong biofilm-forming strains also showed antimicrobial activity and cholesterol removal ability. None of the strains exhibited harmful enzymatic activities. Understanding the interactions and functionality of biofilm-forming bifidobacterial strains is important for their utilization in human health and food or medicine applications.