Commensal microbiota is hepatoprotective and prevents liver fibrosis in mice.

Translocation of bacteria and their products across the intestinal barrier is common in patients with liver disease, and there is evidence that experimental liver fibrosis depends on bacterial translocation. The purpose of our study was to investigate liver fibrosis in conventional and germ-free (GF) C57BL/6 mice. Chronic liver injury was induced by administration of thioacetamide (TAA) in the drinking water for 21 wk or by repeated intraperitoneal injections of carbon tetrachloride (CCl4).

D-Ornithine coopts pyrrolysine biosynthesis to make and insert pyrroline-carboxy-lysine.

D-ornithine has previously been suggested to enhance the expression of pyrrolysine-containing proteins. We unexpectedly discovered that uptake of D-ornithine results in the insertion of a new amino acid, pyrroline-carboxy-lysine (Pcl) instead of the anticipated pyrrolysine (Pyl). Our feeding and biochemical studies point to specific roles of the poorly understood Pyl biosynthetic enzymes PylC and PylD in converting L-lysine and D-ornithine to Pcl and confirm intermediates in the biosynthesis of Pyl.

Metabolomics analysis reveals large effects of gut microflora on mammalian blood metabolites.

Although it has long been recognized that the enteric community of bacteria that inhabit the human distal intestinal track broadly impacts human health, the biochemical details that underlie these effects remain largely undefined. Here, we report a broad MS-based metabolomics study that demonstrates a surprisingly large effect of the gut "microbiome" on mammalian blood metabolites. Plasma extracts from germ-free mice were compared with samples from conventional (conv) animals by using various MS-based methods.

Uropathogenic Escherichia coli CFT073 is adapted to acetatogenic growth but does not require acetate during murine urinary tract infection.

In vivo accumulation of D-serine by Escherichia coli CFT073 leads to elevated expression of PAP fimbriae and hemolysin by an unknown mechanism. Loss of D-serine catabolism by CFT073 leads to a competitive advantage during murine urinary tract infection (UTI), but loss of both D- and L-serine catabolism results in attenuation. Serine is the first amino acid to be consumed in closed tryptone broth cultures and precedes the production of acetyl phosphate, a high-energy molecule involved in intracellular signaling, and the eventual secretion of acetate.

Roles of serine accumulation and catabolism in the colonization of the murine urinary tract by Escherichia coli CFT073.

A D-serine deaminase (DsdA) mutant of uropathogenic Escherichia coli strain CFT073 has a hypercolonization phenotype in a murine model of urinary tract infection (UTI) due to increased virulence gene expression by an unknown mechanism (B. J. Haugen et al.

DsdX is the second D-serine transporter in uropathogenic Escherichia coli clinical isolate CFT073.

d-Serine is an amino acid present in mammalian urine that is inhibitory to Escherichia coli strains lacking a functional dsdA gene. Counterintuitively, a dsdA strain of E. coli clinical isolate CFT073 hypercolonizes the bladder and kidneys of mice relative to wild type during a coinfection in the murine model of urinary tract infection.