Salinity Tolerance and Osmoadaptation Strategies in Four Genera of Anammox Bacteria: , , , and .

The salinity tolerance and osmoadaptation strategies in four phylogenetically distant anammox species, , , , and , were investigated by using highly enriched cell cultures. The first-emerged ". Scalindua sp." showed optimum growth at 1.5-3% salinity and was tolerant to ∼10% salinity (a slight halophile). The second-emerged ". Kuenenia stuttgartiensis" was tolerant to ∼6% salinity with optimum growth at 0.25-1.5% (a halotolerant). These early-emerged ". Scalindua sp." and ″. K. stuttgartiensis" rapidly accumulated K ions and simultaneously synthesized glutamate as a counterion. Subsequently, part of the glutamate was replaced by trehalose. In contrast, the late-emerged ". B. sinica" and ". J. caeni" were unable to accumulate sufficient amounts of K─glutamate and trehalose, resulting in a significant decrease in activity even at 1-2% salinity (nonhalophiles). In addition, the external addition of glutamate may increase anammox activity at high salinity. The species-dependent salinity tolerance and osmoadaptation strategies were consistent with the genetic potential required for the biosynthesis and transport of these osmolytes and the evolutionary history of anammox bacteria: first emerged in marine environments and then and other two species gradually expanded their habitat to estuaries, freshwater, and terrestrial environments, while and likely lost their ability to accumulate K─glutamate.