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Bifidobacterium bifidum strains, an important component of probiotic foods, can form biofilms on abiotic surfaces, leading to increased self-resistance. However, little is known about the molecular mechanism of B. bifidum biofilm formation. A time series transcriptome sequencing and untargeted metabolomics analysis of both B. bifidum biofilm and planktonic cells was performed to identify key genes and metabolites involved in biofilm formation. Two hundred thirty-five nonredundant differentially expressed genes (DEGs) (including vanY , pstS , degP , groS , infC , groL , yajC , tadB and sigA ) and 219 nonredundant differentially expressed metabolites (including L-threonine, L-cystine, L-tyrosine, ascorbic acid, niacinamide, butyric acid and sphinganine) were identified. Thirteen pathways were identified during the integration of both transcriptomics and metabolomics data, including ABC transporters; quorum sensing; two-component system; oxidative phosphorylation; cysteine and methionine metabolism; glutathione metabolism; glycine, serine and threonine metabolism; and valine, leucine and isoleucine biosynthesis. The DEGs that relate to the integration pathways included asd , atpB , degP , folC , ilvE , metC , pheA , pstS , pyrE , serB , ulaE , yajC and zwf . The differentially accumulated metabolites included L-cystine, L-serine, L-threonine, L-tyrosine, methylmalonate, monodehydroascorbate, nicotinamide, orthophosphate, spermine and tocopherol. These results indicate that quorum sensing, two-component system and amino acid metabolism are essential during B. bifidum biofilm formation.

The prevalence of atopic dermatitis (AD) has increased and a therapeutic strategy using probiotic intervention has been reported. The effects of different Bifidobacterium (B. breve, B. bifidum, B. animalis, B. infants, and B. adolescentis) on gut microbial changes were explored in 2,4-dinitrofluorobenzene (DNFB)-induced AD, a T helper type 2-dominant allergic disease. Oral administration of Bifidobacterium suppressed skin thickening and mast cell infiltration, blocked pro-inflammatory cytokines (IL-4, CCL11, IL-13, and CCL22), increased IL-10 and IFN-γ, and modulated the microbiome and ecology in the gut. Based on 16S rRNA results, DNFB treatment resulted in gut microbial dysbiosis, characterized by a decrease in the proportion of Firmicutes and an increase in Bacteroidetes. The core microbiome related to AD were also observed (Dorea , Prevotella , Sutterella , Odoribacter , and Pseudomonas). B. breve and B. bifidum treatments increased the relative abundance of Adlercreutzia , Streptococcus , Lactobacillus , Anaerostipes , and Anaerotruncus. The functional modules involved in fructose and mannose metabolism, propanoate metabolism, and fatty acid biosynthesis were upregulated, and these might be related to immune regulation and short-chain fatty acids (SCFA) production. Taken together, these results suggested that Bifidobacterium treatments affected gut microbial composition and structure, altered gut microbial ecosystem, and these alterations were closely associated with inflammation and SCFA production. [ABSTRACT FROM AUTHOR]

Biofilms are aggregates of microorganisms that adhere to the surface of certain substances and produce extracellular polymers to improve their resistance to stress. However, only some Bifidobacterium strains can form biofilms on abiotic surfaces. The study evaluated the biofilm-forming abilities of six Bifidobacterium strains on grape seed flour (GSF) with a particle size of 80–120 μm. Bifidobacterium animalis, Bifidobacterium bifidum, and Bifidobacterium adolescentis formed weak biofilms, whereas Bifidobacterium pseudo, Bifibacterium breve, and Bifidobacterium longum formed strong biofilms on GSF. B. pseudo cells formed biofilm particles with a diameter of 2 mm, and their cell numbers reached 2.04 × 109 CFU/g at 32 h. There were almost no viable cells in the culture without GSF after 60 h; however, the number of biofilm cells on GSF was still over 106 CFU/g, indicating that biofilms improve cell survival. Field-emission scanning electron microscopy revealed the following stages in the bifidobacterial biofilm formation process: adsorption to GSF, secretion of extracellular substance, biofilm maturation and dispersal, and cell death. Collectively, these results strongly suggest that GSF is beneficial for Bifidobacterial biofilm growth, providing a theoretical basis for the production of highly resistant probiotics in the food industry. • Grape seed flour (GSF) has a porous structure. • Six Bifidobacterium strains can form biofilms on GSF. • B. animalis, B. bifidum, and B. adolescentis formed weak biofilms on GSF. • B. pseudo, B. breve, and B. longum formed strong biofilms on GSF. • Biofilms improve cell survival. [ABSTRACT FROM AUTHOR]

• • Six Bifidobacterium species biofilm formation ability differs. • • All B. bifidum formed strong biofilms. • • B. adolescentis , B. pseudo, B. breve, and B. longum all had biofilm formation and non– biofilm formation strains. • • Gene-trait matching reveals some special genes associated with biofilm phenotype. Biofilm formation by bacteria represents an adaptation strategy to the environment, and some special genes may lead to a strong biofilm phenotype. In this study, we attempted to find functional genes associated with bifidobacterial biofilm formation. Firstly, we evaluated the biofilm formation ability of bifidobacterial strains from six species, which showed that Bifidobacterium longum , Bifidobacterium breve , Bifidobacterium animalis , Bifidobacterium adolescentis , and Bifidobacterium pseudocatenulatum had biofilm-forming and non-biofilm-forming strains, while all Bifidobacterium bifidum strains could form strong biofilms. Then 48 strains were selected for genome sequencing and comparative analysis. The gene-trait matching analysis revealed that B. bifidum biofilm formation phenotype may associate with their unique genes, involving in stress response, quorum sensing, two components, and peptide synthesis. B. pseudocatenulatum biofilm formation was positively correlated with the eps cluster (rfbX). While no genotype related to the biofilm phenotype was found in B. longum using this analysis, but all contain autoinducer-2 (AI-2) receptor genes. Moreover, luxS, rbsB, rfbX were selected for real-time qPCR analysis, suggesting that their expression are important to biofilm formation. These results indicated that strains carrying certain genes tend to form stronger biofilms than those formed by strains without these genes. [ABSTRACT FROM AUTHOR]