Broad similarities in AOA amoA gene sequences predict potentially

Broad similarities in AOA amoA gene sequences predict potentially similar AMO structure and therefore similar sensitivities to photoinhibition, while phylogenetic separation of AOA and AOB sequences and other physiological distinctions between archaea and bacteria suggest that levels of photoinhibition may differ and may

give rise to niche differentiation, which is supported by our results. The effect of light on AOA has not previously been investigated. This study therefore provides the first evidence of photoinhibition in AOA and significantly greater this website inhibition of AOA than that of AOB. In addition, the study demonstrates differences in photosensitivity within AOB and AOA. Photoinhibition may therefore contribute to niche differentiation between and within AOA and AOB and may determine their distribution

and diversity in light-affected ecosystems. Our findings influence explanations for several phenomena in aquatic environments. Nitrite often accumulates at the base of the euphotic zone, forming the primary nitrite maximum, which is explained by either nitrate reduction to nitrite, by light-limited phytoplankton or by differential photoinhibition of ammonia oxidizers and nitrite oxidizers (Lomas & Lipschultz,2006). While other environmental factors may drive the distribution of AOA and AOB, the latter hypothesis assumes a key role for photoinhibition of ammonia oxidizers in surface waters, which is relieved with increasing depth, as light intensity decreases. selleck screening library It further assumes that nitrite oxidizers are more photosensitive than ammonia oxidizers, leading to the accumulation of nitrite through greater inhibition of nitrite production and/or slower recovery following photoinhibition. Cultivation-based studies provide contradictory evidence for this hypothesis, indicating that AOB are more photosensitive than nitrite oxidizers (Guerrero & Jones, 1996a), but that they recover more quickly from photoinhibition when subsequently incubated in the dark (Guerrero & Jones, 1996b). However, this model was developed prior to the

discovery of the dominance of AOA in marine ecosystems. Greater photoinhibition ZD1839 cell line and slower recovery of AOA, compared with AOB, observed in our study suggest that the difference between photoinhibition of ammonia and nitrite oxidizers is less than previously thought, reducing confidence in this explanation of the nitrite maximum. The light intensities investigated are similar to those causing in situ inhibition of nitrification in previous studies: 100 μE m−2 s−1 in the eutrophic Delaware River (Lipschultz et al., 1985) and approximately 40–70 μE m−2 s−1 in a Californian bight (Olson, 1981). In the mixed layer of natural aquatic systems, however, turbidity may promote nitrification both by protecting nitrifiers from photoinhibition and by limiting substrate competition with phytoplankton.

This entry was posted in Uncategorized. Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *


You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>