Photoinhibition of marine nitrifying bacteria. I. Wavelength-dependent response

Abstract

Axenic cultures of chemolithotrophic nitrifying bacteria (NH, ' and NOz-oxidizers) respond to light in distinct manners. After short-term (2 to 4 h ) monochromatic irradiations both types of nitrifying bacteria demonstrated a widespread photosensitivity in the near-UV region (300 to 375 nm) and a differential photosensitivity in the blue region of the spectrum (400 to 475 nm). Nitrite oxidizers were less sensitive overall to blue llght inhibition than were ammonium oxidizers. Character~stically, the extent of the photoinhibition was species-specific and light response was dose-and wavelength-dependent. Photoprotection by higher substrate concentrations was only observed with ammonium oxidizers. Increased cell densities altered the phototolerance of nitrite oxidizers and made these organisms light-susceptible. Similarly, treatment wlth a low light dose for extended periods was more damaging to nitrite oxidizers, when high cell densities were used. Polychromatic irradiations served to confirm the monochromatic results. Cool-white fluorescent light inhibited NH,' oxidizing activity but not NO2-oxidizing activity. Exposure to sunlight resulted in inhibition of activity in both types of nitrif~e r s .These data demonstrate that the effect of light on autotrophic nitrification depends not only on the type of nitrifier (NH,' or N O 2 oxidizer), but also on the conditions of their environment.

Origin, causes and effects of increased nitrite concentrations in aquatic environments

“…This results in the spatial separation of the two stages of nitrification in marine environments, from which the position of a nitrite maximum in near surface seawater can be explained (Olson 1981). Treatment with a low light dose for extended periods was more damaging to NOB (Guerrero & Jones 1996). Bock (1965) attributes this greater sensitivity of NOB to the relatively low cytochrome c content of Nitrobacter compared to Nitrosomonas.…”

“…Bock (1965) attributes this greater sensitivity of NOB to the relatively low cytochrome c content of Nitrobacter compared to Nitrosomonas. Guerrero and Jones (1996) concluded that the effect of light depends on the type of nitrifier as well as on the conditions of the environment. They also found that phototolerance of NOB was altered by increased cell concentrations which made these organisms light susceptible.…”

Vertical stability and the annual dynamics of nutrients and chlorophyll fluorescence in the coastal, southeast Beaufort Sea

“…On the vertical, the association between the nitrite maximum, the SCM and the nitracline (Figure 6) strongly suggests that the NO 2 À was released by phytoplankton, possibly because irradiance at the SCM was not always sufficient to drive the complete reduction of NO 3 À or because shade-adapted algae used NO 3 À reduction as an electron sink when transiently exposed to higher light intensities [Lomas and Glibert, 1999]. Phytoplankton are hypothesized to be the principal cause of formation and maintenance of the primary nitrite maximum in other stratified oceans (see references given by Lomas and Lipschultz [2006]), which is even more likely in the Beaufort Sea where the maximum is shallow enough for light to inhibit NH 4 + oxidizers during summer [e.g., Guerrero and Jones, 1996]. If this is true, then the NO 3 À produced by the wintertime nitrification of the NO 2 À released in the primary nitrite maximum during summer should be considered allochthonous and not recycled, since the N was not assimilated into biomass.…”

Benthic fluxes of oxygen and nutrients in sublittoral fine sands in a north-western Mediterranean coastal area

“…These differences were due to microphytobenthos nutrient demand that involves nutrient fixation from water column and pore-water. Furthermore, NO 2 -+NO 3 -could be influenced by nitrification inhibition in light conditions (Guerrero and Jones, 1996;Herbert, 1999) According to DO daily fluxes, the well-sorted fine sands behaved as autotrophic only during spring, influenced by high average incident irradiance, thereby leading to a lower DIN release from sediments because of microphytobenthic fixation. Annual metabolic cycle could be linked with light pattern owing to the strong correlation observed between DO daily fluxes and Ī z (r=0.98, p<0.01).…”