Abstract
Bacteroidales are the most abundant Gram-negative bacteria flourished in the human intestine with great underlying benefits to be discovered and developed as the next-generation probiotics. However, the traditional isolation method limits the mining of low-abundant species. In this study, modified selective medium was established using xylan as the sole carbohydrate source to enrich low-abundant species such as Prevotella copri and Bacteroides xylanisolvens from healthy human fecal samples. The growth rate, transcriptomics, and metabolomics profiles of the enriched low-abundant species were then evaluated. The considerable upregulated genes encoding xylan-associated hydrolysis and transportation, along with the increased xylose production detected in the culture of the enriched Bacteroidales strains based on xylan, were considered as positive proof of the feasibility of the modified methodology.
Highlights
Species or strains with health beneficial functions in addition to the traditional probiotics such as Lactobacillus and Bifidobacterium are under exploiting to be novel new-generation probiotics, of which Bacteroidales species, the most abundant Gram-negative bacteria flourished in human intestine, are one of the most potential candidates (O’Toole et al, 2017)
The well acknowledged techniques for isolating Bacteroidales resort to the Brucella laked blood, kanamycin, and vancomycin medium (LKV) (Zitomersky et al, 2011), through which the difficulties of purifying certain species are determined by their abundance in the sample and Isolation of Low-Abundant Bacteroidales thereby the Bacteroidales species in the healthy human intestine with relatively high abundance of over 1%, which corresponds to B. uniformis, B. vulgatus, B. caccae, Parabacteroides distasonis, P. merdae, and Alistipes putredinis as identified by the nextgeneration sequencing techniques (Tap et al, 2009; Qin et al, 2010; Jeffery et al, 2016), are much easier to be obtained
From the results of the bacterial isolation from both fecal samples and the Bacteroidales consortium, as shown in Tables 2A,B, more probable number of colonies corresponding to B. ovatus, B. uniformis, and B. thetaiotaomicron could be picked out from the control medium, which was a modified version of the standard selective medium for general Bacteroidales species
Summary
Species or strains with health beneficial functions in addition to the traditional probiotics such as Lactobacillus and Bifidobacterium are under exploiting to be novel new-generation probiotics, of which Bacteroidales species, the most abundant Gram-negative bacteria flourished in human intestine, are one of the most potential candidates (O’Toole et al, 2017). Low-abundant species exhibit beneficial talents, such as B. xylanisolvens, which was confirmed to promote the suppression of cancer development via inducing the TFα-specific immunoglobulin M serum antibodies (Ulsemer et al, 2016), and B. acidifaciens JCM10556, which facilitates the maintenance of intestinal mucosa by stimulating the secretion of immunoglobulin A and thereby elevating pathogens that have breached the epithelial walls (Yanagibashi et al, 2013). Methodologies for purifying these low-abundant Bacteroidales species are worth exploration
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