DIVERSITY, DISTRIBUTION AND ENVIRONMENTAL PREFERENCES OF NITRITE OXIDIZING BACTERIA IN THE ETNP

Abstract

Novel species of nitrite oxidizing bacteria (NOB) have been found in the oxycline and the anoxic core of the oxygen minimum zone (OMZ) of the Eastern Tropical South Pacific (ETSP). The contrasting distribution of the putatively anaerobic NOB throughout the OMZ likely indicates that the novel NOBs have different oxygen preferences. In this study, simple contigs from metagenomes of samples taken from the Eastern Tropical North Pacific (ETNP) are used to identify nxrB genes. Phylogenetic trees of the nxrB hits are utilized to understand the distribution and relationship of nxrB at different depths, sampling locations, and incubation conditions. No nxrB hits were found in samples taken from the surface of the OMZ and all hits were found in samples taken from the secondary chlorophyll maximum (SCM). NxrB hits did not cluster due to sampling depth, location, or incubation, instead they were grouped by phylogenetic node. These results lend support to the theory of the ‘cryptic oxygen cycle’ in that some NOBs are specific to conditions unique to the SCM of OMZs and shows that there is a larger diversity of NOB adapted to these conditions than previously thought.