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.S ymbioses between animals and chemosynthetic bacteria are widespread in Earth's oceans 1 . Animals from at least seven phyla have formed such symbioses, and even more chemosynthetic bacterial lineages have evolved symbioses with animal hosts 1 . Chemosynthetic symbionts can use a range of chemicals, such as sulfide, methane, hydrogen and carbon monoxide, to power their metabolism 2-4 . The hosts of chemosynthetic symbionts dominate some animal communities. For example, shallow-water lucinid bivalves, which host sulfur-oxidizing symbionts, often dominate the macrobenthic infaunal community in seagrass meadows, where they can reach densities greater than 3,500 individuals per square metre 5,6 . Their diversity in nature, their persistence over evolutionary timescales and their dominance in many habitats attest to the success of these symbiotic partnerships 1 .Chemosynthetic symbionts are primarily considered 'nutritional symbionts', meaning their primary role is to provide nutrition for their hosts 1,7 . So far, most studies have focused on inorganic carbon fixation by the symbionts and the transfer of fixed organic carbon compounds to the hosts. In addition to organic carbon, all animals require a source of fixed nitrogen. However, nitrogen metabolism in chemosynthetic symbioses has received far less attention. Chemosynthetic symbionts have been shown to gain their nitrogen from ammonium or nitrate in their environment 8-10 and co-occurring nitrogen-fixing and chemosynthetic symbionts have been found in cold-water corals 11 . Nitrogen fixation by chemosynthetic symbionts has long been hypothesized, but so far not yet shown [12][13][14] .Our study focused mainly on the endosymbiosis between bivalves of the family Lucinidae and sulfur-oxidizing bacteria. Lucinids are by far the most diverse and widespread group of bivalves that host chemosynthetic symbionts 15 . There are at least 400 living species, occupying a range of habitats including mangrove sediments, seagrass beds, coral reef sediments and coastal mud and sand 16 . In seagrass...
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.
Due to more and more restrictive emission standards, the air system of Diesel engines has evolved into a complex system with several coupled actuating and controlled variables. In this paper, a linear-quadratic regulator (LQR) is used as a model-based, multivariable, optimal control of the air system. This technique is validated by results of an on-board test.
In many applications with dynamical processes parameter depending systems of nonlinear ordinary differential equations (ODE) are formulated. Often the model description does not perfectly match with realistic data. SQP-methods can be used to identify the parameters of the dynamical model. In conventional approaches the ODE system is solved numerically several times during each of the iteration steps of the optimization process. In this work it is proposed to perform the numerical integration of the ODE system within the optimization process. The benefits of the presented technique will be illustrated by the application of a turbocharger design within the context of diesel engined vehicle development.
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