[Halomonas campisalis, an obligatorily alkaliphilic, nitrous oxide-reducing denitrifier with a Mo-cofactor-lacking...

We isolated eight strains of denitrifying bacteria that reduce nitrate and nitrous oxide at pH 10 from Lake Magadi (Kenya). Despite certain differences between the strains, they are similar in terms of G+C content (66.1-68.1 mol %) and DNA-DNA homology (75-92%) and represent different morphotypes of the same species. Based on the results of partial 16S rRNA sequencing, strain Z-7398-2 was most closely related to the Halomonas campisalis isolate from Alkali Lake (USA). The DNA-DNA homology level between the tested strain and the type strain of H. campisalis 4A was 88%. These two strains were also similar phenotypically. However, the culture isolated by us was characterized by peculiar properties, such as obligate alkaliphily, which manifested itself in the culture dependence on carbonates and lack of growth at pH values below 7, a nitrous oxide-reducing capacity, and an unusual nitrate reductase that lacked molybdenum and a Mo cofactor.