Author Correction: Chemosynthetic symbionts of marine invertebrate animals are capable of nitrogen fixation.

In this Article, the completeness and number of contigs for draft genomes from two individuals of Laxus oneistus are incorrect in the main text, although the correct information is included in Table 1. The original and corrected versions of the relevant sentence are shown in the correction notice.

Ereboglobus luteus gen. nov. sp. nov. from cockroach guts, and new insights into the oxygen relationship of the genera Opitutus and Didymococcus (Verrucomicrobia: Opitutaceae).

We isolated a novel member of the phylum Verrucomicrobia from the hindgut of the cockroach Shelfordella lateralis. Strain Ho45 is a yellow-pigmented, motile coccus that represents a new genus-level lineage with less than 93% sequence similarity to the 16S rRNA genes of other species in the family Opitutaceae. Ultrastructural analysis revealed a Gram-negative cell envelope with an outer membrane and a periplasmic space. In its ability to ferment sugars to propionate and acetate as major products, strain Ho45 resembles its closest relative, Opitutus terrae. However, the strains differed in their relationship to oxygen. Although strain Ho45 grew and consumed oxygen at sub-atmospheric concentrations (1-4%), both growth rate and cell yield decreased strongly with increasing oxygen concentration in the headspace. By contrast, O. terrae, previously described as an obligate anaerobe, proved to be facultatively aerobic, with highest growth rates and cell yields at 2% and 16% oxygen, respectively. Also the closely related Didymococcus (Diplosphaera) colitermitum, previously described as an obligately aerobic microaerophile, showed a fermentative metabolism under anoxic conditions, forming the same products from glucose as strain Ho45 and O. terrae. Based on phenotypic and phylogenetic evidence, we propose strain Ho45 as the type strain of a novel genus, Ereboglobus luteus gen. nov. sp. nov., and provide an emended description of the family Opitutaceae and the genera Opitutus and Didymococcus.

Chemosynthetic symbionts of marine invertebrate animals are capable of nitrogen fixation.

Chemosynthetic symbioses are partnerships between invertebrate animals and chemosynthetic bacteria. The latter are the primary producers, providing most of the organic carbon needed for the animal host's nutrition. We sequenced genomes of the chemosynthetic symbionts from the lucinid bivalve Loripes lucinalis and the stilbonematid nematode Laxus oneistus. The symbionts of both host species encoded nitrogen fixation genes. This is remarkable as no marine chemosynthetic symbiont was previously known to be capable of nitrogen fixation. We detected nitrogenase expression by the symbionts of lucinid clams at the transcriptomic and proteomic level. Mean stable nitrogen isotope values of Loripes lucinalis were within the range expected for fixed atmospheric nitrogen, further suggesting active nitrogen fixation by the symbionts. The ability to fix nitrogen may be widespread among chemosynthetic symbioses in oligotrophic habitats, where nitrogen availability often limits primary productivity.