Abstract
Genomic analysis was performed on seven strains of Bifidobacterium thermacidophilum, a Sus-associated Bifidobacterium. Three strains from the feces of domestic pigs (Sus scrofa domesticus) and four strains from the rectal feces of free-range Japanese wild boars (S. s. scrofa) were compared. The phylogenetic position of these isolates suggested by genomic analyses were not concordant with that suggested by 16S rRNA sequence. There was biased distribution of genes for virulence, phage, metabolism of aromatic compounds, iron acquisition, cell division, and DNA metabolism. In particular four wild boar isolates harbored fiber-degrading enzymes, such as endoglucanase, while two of the pig isolates obtained from those grown under an intensive feeding practice with routine use of antimicrobials, particularly tetracycline harbored a tetracycline resistance gene, which was further proved functional by disk diffusion test. The tetW gene is associated with a serine recombinase of an apparently non-bifidobacterial origin. The insertion site of the tetW cassette was precisely defined by analyzing the corresponding genomic regions in the other tetracycline-susceptible isolates. The cassette may have been transferred from some other bacteria in the pig gut.
Highlights
Pig intestinal microbiota were investigated in terms of their functionalities in host health and growth promotion (Lee and Mazmanian, 2010; Brestoff and Artis, 2013)
Seven bifidobacterial strains were isolated from pigs or wild boars
According to 16S rRNA phylogeny, isolates were separated into two clusters: one was composed of pig isolates identified as B. thermacidophilum subsp. porcinum with a 99% identity of the 16S rRNA sequence, and the other was composed of wild boar isolates identified as B. thermacidophilum subsp. thermacidophilum with a 98–99% identity of the 16S rRNA gene sequence
Summary
Pig intestinal microbiota were investigated in terms of their functionalities in host health and growth promotion (Lee and Mazmanian, 2010; Brestoff and Artis, 2013). The development of pig intestinal microbiota, the predominance of Lactobacillus spp., is considered a key event for health promotion (Konstantinov et al, 2006; Petri et al, 2010), and this lactobacillal predominance may relate to the significant reduction of Enterobacteriaceae and Clostridium perfringens (Inoue et al, 2005). Such development is affected by the weaning, dietary changes, and host-immune development (Katouli et al, 1997; Mackie et al, 1999; Inoue and Ushida, 2003; Ushida et al, 2008). We need to identify and isolate the Suidae-associated Bifidobacterium carried by both wild boars and domestic pigs
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