Photoinhibition and recovery of NH4+-oxidizing bacteria and NO2--oxidizing bacteria.

Abstract

The effects of illumination on nitrifying bacteria were investigated with and without substrate. NH4+-oxidizing bacteria (strain H-1, probably Nitrosospira sp.) and N02--oxidizing bacteria (strain 0-1, probably Nitrobacter sp.), isolated from Lake Kizaki, were inhibited by light (about 75 ,uEinsteins/m2/sec,12-hr light: 12-hr dark). Photoinhibited H-1 and 0-1 cells recovered after several to tens of days under dark conditions. However, H-1 cells, illuminated for 7 to 10 days in the absence of NH4+, did not produce N02-significantly for 120 to 350 days in a medium containing 50 uM NH4+. The substrate (NH4+) was found to protect H-1 from photoinhibition, while such an effect of N02-on 0-1 was not so clear. 0-1 was more sensitive to light than H-1 in the short illumination period. However, the inhibitory effect of prolonged illumination was greater on H-1 than on 0-1. It was indicated from growth kinetic analysis that the photoinhibitory effects on both NH4+-oxidizing bacteria and N02--oxidizing bacteria were not only lethal but also bacteriostatic. Nitrification, which is an important microbiological process in the nitrogen cycle, is affected by substrate (NH4+ and N02-) concentration, temperature, oxygen content, pH, and Eh. Light has an inhibitory effect on nitrifying bacteria (1, 2). OLSON (3, 4) and WARD et al. (5) suggested that the formation of the primary nitrite maximum in the ocean was due to the differential photoinhibition of nitrifying bacteria. HORRIGAN et al. (6) found that nitrifying bacteria isolated from sea-surface film were inhibited by light and that no nitrification occurred in the surface films of subtropical seas. From the point of view of the recovery from photoinhibition of nitrifying bacteria, HOOFER and TERRY (7) observed that Nitrosomonas europaea cells 90 %-inactivated by illumination recovered their full activity after 10 hr. HORRIGAN et al, (6) cited the fact that light inhibition was not lethal and that nitrifiers might recover when they mixed to depths of sufficiently low light levels in the sea. In Lake Kizaki, the nitrifying activity of lake water is very low in l51

Cascading trophic effects on aquatic nitrification: experimental evidence and potential implications

“…Studies of nitrification in marine pelagic environments, reviewed by Kaplan (1983) and Ward (1986), indicate that natural populations of nitrifiers can oxidize their substrates at rates several orders of magnitude higher than those predicted from pure cultures. Furthermore, nitrification was detected under 24 h light cycle incubations in the photic zone (Ward 1986), suggesting that light inhibition may be not so severe in the surface waters as previously believed (Yoshioka & Sajo 1984). Nitrification occurs in such extreme environments as hot springs (Bock et al 1989) and Antarctic ice (Arrigo et al 1995).…”

PISCES-v2: an ocean biogeochemical model for carbon and ecosystem studies

“…It is assumed to be photo-inhibited (e.g., Horrigan et al, 1981;Yoshioka and Saijo, 1984) and reduced in suboxic waters:…”

Influence of light on bacterioplankton production and respiration in a subtropical coral reef

“…Whereas light has long been recognized as a factor influencing photosynthesis (Kirk 1994) and the activities of fish and zooplankton (Kampa 1976), the influence of light on the activities of non-photosynthetic aquatic bacteria has only recently been appreciated. Photoinhibition of nitrifying bacteria has been demonstrated in both the field and the laboratory (Hooper & Terry 1974, Ward 1985, Yoshioka & Saijo 1985, Vanzella et al 1989, Horngan & Springer 1990) and has been invoked as a mechanism influencing the spatial distribution of NH,+ and NO2-oxidization in rivers, estuaries and pelagic marine ecosystems (Olsen 1981, Lipshultz et al 1985, Owens 1986). Exposure to solar radiation similarly influences the production and metabolism of heterotrophic bacteria directly, by photoinhibition (Bailey et al 1983, Sieracki & Aquat M~c r o b Ecol 14: 137-148, 1998 Sieburth 1986, Herndl, et al 1993, Miiller-Niklas et al …”