Horizontal gene transfer of "prototype" Nramp in bacteria

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Eukaryotic Nramp proteins function as divalent metal ion transporters, crucial for nutrition and immunity.
• Bacterial homologs, MntH, are proton-dependent transporters classified into homology groups A, B, and C, with C further divided into Cα, Cβ, and Cγ.

Purpose of the Study:

• To investigate the functional conservation and evolutionary history of bacterial MntH transporters.
• To explore evidence for horizontal gene transfer (HGT) in the dissemination of mntH genes, particularly mntH C.

Main Methods:

• Comparative analysis of MntH protein sequences and hydropathy profiles.
• Functional characterization by expressing bacterial MntH proteins in E. coli to assess metal transport activity.
• Genomic analysis to identify associations of mntH genes with mobile genetic elements and tRNA genes.

Main Results:

• Bacterial MntH B and C proteins from C. tepidum and E. faecalis, respectively, demonstrated conserved divalent metal transport function when expressed in E. coli.
• Genomic evidence strongly suggests HGT of mntH C genes, with associations to tRNA, mobile DNA elements, and sequence similarities between eukaryotic Nramp and bacterial MntH Cα.
• Intronless Nramp genes in invertebrates may represent a source for Nramp gene transfer to bacteria.

Conclusions:

• Bacterial MntH transporters exhibit functional conservation across different homology groups.
• Horizontal gene transfer has played a significant role in the evolution and distribution of bacterial mntH genes.
• Eukaryotic Nramp genes are proposed as ancestral to bacterial MntH C proteins, potentially facilitating bacterial pathogenesis.