Neutrophil chemotaxis in systemic lupus erythematosus.

Abstract

<h3>Abstract</h3> Microbial nitrification is a critical process governing nitrogen availability in aquatic systems and provides energy for aphotic carbon fixation. Nitrifiers are phylogenetically and physiologically diverse, but the factors controlling this diversity, and its biogeochemical implications, are poorly understood, particularly in freshwater systems. Here, we characterized the taxonomic, genomic, and metabolic diversity of free-living nitrifiers across Earth’s largest freshwater system, the Laurentian Great Lakes. Surprisingly, ammonia oxidizing Bacteria (AOB) related to <i>Nitrosospira</i> dominated over ammonia oxidizing Archaea (AOA) at most stations, even in oligotrophic lakes with extremely low substrate concentrations. Nitrite oxidizing Bacteria (NOB) <i>Ca</i>. Nitrotoga and <i>Nitrospira</i> each dominated a subset of stations, even switching within a lake. Among four ecotypes of <i>Nitrosospira</i> we identified, one encodes proteorhodopsin, which could enhance survival of this AOB in transparent, low nutrient lakes. Genome reconstructions for free-living AOA, AOB, and NOB indicate small genomes across all taxa and diverse adaptations to sunlight and oxidative stress. Our findings expand the known functional diversity of nitrifiers and provide the first integrated picture of freshwater nitrifier genomics and ecology. As lakes worldwide undergo rapid environmental change, understanding the relationship between microbial biodiversity and nitrogen cycling is essential for predicting future ecosystem health and services.