Identification of a proton-chloride antiporter (EriC) by Himar1 transposon mutagenesis in Lactobacillus reuteri and its role in histamine production

Antonie Van Leeuwenhoek. 2014 Mar;105(3):579-92. doi: 10.1007/s10482-014-0113-8. Epub 2014 Feb 1.

Abstract

The gut microbiome may modulate intestinal immunity by luminal conversion of dietary amino acids to biologically active signals. The model probiotic organism Lactobacillus reuteri ATCC PTA 6475 is indigenous to the human microbiome, and converts the amino acid L-histidine to the biogenic amine, histamine. Histamine suppresses tumor necrosis factor (TNF) production by human myeloid cells and is a product of L-histidine decarboxylation, which is a proton-facilitated reaction. A transposon mutagenesis strategy was developed based on a single-plasmid nisin-inducible Himar1 transposase/transposon delivery system for L. reuteri. A highly conserved proton-chloride antiporter gene (eriC), a gene widely present in the gut microbiome was discovered by Himar1 transposon (Tn)-mutagenesis presented in this study. Genetic inactivation of eriC by transposon insertion and genetic recombineering resulted in reduced ability of L. reuteri to inhibit TNF production by activated human myeloid cells, diminished histamine production by the bacteria and downregulated expression of histidine decarboxylase cluster genes compared to those of WT 6475. EriC belongs to a large family of ion transporters that includes chloride channels and proton-chloride antiporters and may facilitate the availability of protons for the decarboxylation reaction, resulting in histamine production by L. reuteri. This report leverages the tools of bacterial genetics for probiotic gene discovery. The findings highlight the widely conserved nature of ion transporters in bacteria and how ion transporters are coupled with amino acid decarboxylation and contribute to microbiome-mediated immunomodulation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Antiporters / genetics*
  • Antiporters / metabolism*
  • Biological Transport
  • Chlorides / metabolism
  • DNA Transposable Elements*
  • Gene Expression
  • Gene Expression Regulation, Bacterial
  • Gene Order
  • Gene Silencing
  • Genetic Vectors / genetics
  • Histamine / biosynthesis*
  • Histidine Decarboxylase / genetics
  • Lactobacillus reuteri / drug effects
  • Lactobacillus reuteri / genetics*
  • Lactobacillus reuteri / metabolism*
  • Multigene Family
  • Mutagenesis*
  • Mutagenesis, Insertional
  • Probiotics
  • Promoter Regions, Genetic
  • Protons
  • Tumor Necrosis Factors / pharmacology

Substances

  • Antiporters
  • Chlorides
  • DNA Transposable Elements
  • Protons
  • Tumor Necrosis Factors
  • Histamine
  • Histidine Decarboxylase