AUTHOR=Roalkvam Irene , Drønen Karine , Stokke Runar , Daae Frida Lise , Dahle Håkon , Steen Ida Helene 

TITLE=Physiological and genomic characterization of Arcobacter anaerophilus IR-1 reveals new metabolic features in Epsilonproteobacteria

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.00987

DOI=10.3389/fmicb.2015.00987

ISSN=1664-302X

ABSTRACT=<p>In this study we characterized and sequenced the genome of <italic>Arcobacter anaerophilus</italic> strain IR-1 isolated from enrichment cultures used in nitrate-amended corrosion experiments. <italic>A. anaerophilus</italic> IR-1 could grow lithoautotrophically on hydrogen and hydrogen sulfide and lithoheterothrophically on thiosulfate and elemental sulfur. In addition, the strain grew organoheterotrophically on yeast extract, peptone, and various organic acids. We show for the first time that <italic>Arcobacter</italic> could grow on the complex organic substrate tryptone and oxidize acetate with elemental sulfur as electron acceptor. Electron acceptors utilized by most <italic>Epsilonproteobacteria</italic>, such as oxygen, nitrate, and sulfur, were also used by <italic>A. anaerophilus</italic> IR-1. Strain IR-1 was also uniquely able to use iron citrate as electron acceptor. Comparative genomics of the <italic>Arcobacter</italic> strains <italic>A. butzleri</italic> RM4018, <italic>A. nitrofigilis</italic> CI and <italic>A. anaerophilus</italic> IR-1 revealed that the free-living strains had a wider metabolic range and more genes in common compared to the pathogen strain. The presence of genes for NAD<sup>+</sup>-reducing hydrogenase (<italic>hox</italic>) and dissimilatory iron reduction (<italic>fre</italic>) were unique for <italic>A. anaerophilus</italic> IR-1 among <italic>Epsilonproteobacteria</italic>. Finally, the new strain had an incomplete denitrification pathway where the end product was nitrite, which is different from other <italic>Arcobacter</italic> strains where the end product is ammonia. Altogether, our study shows that traditional characterization in combination with a modern genomics approach can expand our knowledge on free-living <italic>Arcobacter</italic>, and that this complementary approach could also provide invaluable knowledge about the physiology and metabolic pathways in other <italic>Epsilonproteobacteria</italic> from various environments.</p>