Diversity in CO 2 -Concentrating Mechanisms among Chemolithoautotrophs from the Genera Hydrogenovibrio , Thiomicrorhabdus , and Thiomicrospira , Ubiquitous in Sulfidic Habitats Worldwide

Autotrophic organisms take up and fix DIC, introducing carbon into the biological portion of the global carbon cycle. The mechanisms for DIC uptake and fixation by autotrophicBacteria andArchaea are likely to be diverse but have been well characterized only for “Cyanobacteria .” Based on genome sequences, members of the generaHydrogenovibrio ,Thiomicrospira , andThiomicrorhabdus have a variety of mechanisms for DIC uptake and fixation. We verified that most of these organisms are capable of growing under low-DIC conditions, when they upregulate carboxysome loci and transporter genes collocated with these loci on their chromosomes. When these genes, which fall into four evolutionarily independent families of transporters, are expressed inE. coli , DIC transport is detected. This expansion in known DIC transporters across four families, from organisms from a variety of environments, provides insight into the ecophysiology of autotrophs, as well as a toolkit for engineering microorganisms for carbon-neutral biochemistries of industrial importance.