English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Recovery of activity by 2 marine nitrifying bacteria, Nitrosomonas cryotolerans and Nitrobacter sp. Nb297, was monitored after exposure to light and/or carbon monoxide. N. cryotolerans recovered more rapidly after exposure to artificial light (25 W m-') than CO (11.4 PM). The adhtion of 100 yM NH,+ during the time of light or CO exposure allowed the cells to recover faster and decreased the difference observed between the inhibitory effects of light and CO. Cells exposed to sunlight recovered much illore slowly than cells exposed to either CO or artificial hght. The ammonium oxidizer N. cryotolerans when exposed to sunlight (2 h) recovered up to 35 "/o of its original ammonium oxidizing activity. Recovery increased to 57 % in the presence of additional substrate (100 pM NH,'). The nitrite oxidizer Nitrobactersp. Nb297 did not show a noticeable recovery from sunlight whether substrate was added or not. INTRODUCTION without the addition of substrate. A better understanding of this is necessary to aid in answering questions In the oceans, chemolithotrophic nitrifying bacteria dealing with the formation of the nitrite maximum and (ammonium and nitrite oxidizers) are subjected to the ecological importance of these bacteria which repreperiods of low nutrient availability (Morita 1982, Jones sent a link between the carbon and nitrogen cycles in & Morita 1985). During these periods, nitrifying organaquatic systems (Karl e t al. 1984, Morita & Jones 1986). isms may be subjected to additional stresses such as light (Miiller-Neugluck & Engel 1961, Hooper & Terry 1974, Horrigan et al. 1981, Olson 1981a, b, Yoshioka & MATERIALS AND METHODS Saijo 1984, 1985, Shears & Wood 1985, Ward 1985) and CO (Hooper & Terry 1973, Suzuki et al. 1976, Jones & Cultures. The marine ammonium oxidizing bacMorita 1984a, b). Olson (1981b) reported different patterium Nitrosomonas cryotolerans (Jones et al. 1988), terns of photoinhibition for marine nitrifiers; ammoand the nitrite oxidizing bacteria Nitrobacter sp. Nb297 nium oxidizers appeared to be less sensitive to light (provided by S. W. Watson) were grown in the dark, in than nitrite oxidizers. Further, it was postulated that the 4 1 chemostat culture units (0.14 d' dilution rate) primary nitrite maximum is a consequence of the differequipped with automatic pH control that maintained a ential inhibition observed (Olson 1981b). PhotochemipH of 7.8 f 0.05 by addition of 5 % K2C03. Ammonium cally formed CO is moreover a common feature in the oxidizer medium contained 0.011 M of NH4+ as oceans (surface concentrations of 2 to 100 nM; Conrad (NH4)2S04 and the salinity was adjusted to 30 %O using & Seiler 1980, 1985, Conrad et al. 1982). Cycling of Instant Ocean Synthetic Sea Salts (Aquarium Systems, nitrogen in the surface waters of the sea may therefore Inc., Mentor, Ohio; Jones & Hood 1980). Nitrite oxidizdepend upon the ability of these organisms to recover ers were cultured in the same manner in the medium of from light and CO. Vanzella et al. (1989) showed that Watson & Waterbury (1971). The concentration of NO2high substrate concentration benefits actively growing as NaN02 was 0.029 M. Cultures were vigorously aermarine nitrifiers since it increased their tolerance to ated, agitated by a magnetic stirring bar, and kept at a these inhibitors. constant temperature of 25 "C. This paper examines the ability of marine nitrifying Preparation of standard inoculum. Cells were harbacteria to recover from Light and CO inhibition, with or vested from 250 m1 chemostat culture by centrifugation O Inter-ResearcWPrinted in F. R. Germany =2 Mar. Ecol. Prog. Ser. 60: 91-95, 1990 (6000 X g; 15 min; 5"C), washed twice with filtered (Whatman GF/C, 1.2 {(m) Sargasso Sea water (SSW), containing 0.02 M N-2-hydroxyethylpiperazine-N-2ethanesulfonic acid (HEPES) pH 7.8, and then resuspended in 10 m1 of SSW. Cell density was determined using a Petroff-Hauser counting chamber. From this suspension, 0.1 m1 was inoculated into a 60 m1 sterile serum bottle containing 25 m1 of SSW. The final cell density was ca 5 X 10' cells ml-' for the ammonium oxidizer and 1.1 X 10%ells ml-' for the nitrite oxidizer. SSW used for the preparation of cell suspensions had been previously purged for 15 min with CH4and COfree air to remove dissolved C O and CH4. SSW was low enough in nutrients such that it did not interfere with the results (< 20 nM NH, +; < 10 nM NO2-; < 20 nM NO3-). Neither ammonium nor nitrite oxidation was detected in SSW. .U! experiments described below were replicated and samples within each experiment were collected and analyzed in triplicate. All data points reported are mean values of the replicates in individual experiments and fell within a 95 O/O confidence interval. Statistical inferences were made using a I-way analysis of variance (ANOVA), F values were determined and experimental values were found to be significantly different if p was < 0.01. Exposure and recovery from CO inhibition. After inoculation, (NH4)2S04 was added to a final concentration of 0 or 100 1tM NH,'. Bottles were sealed with serum stoppers and C O was injected into the headspace to give final concentrations of 11.4 !tM (Schmidt 1979, Vanzella e t al. 1989). Exposure times ranged from 1 to 3 h. Bottles were incubated in the dark at 25 "C on a rotatory shaker a t 150 rpm. After exposure, cells were harvested by centrifugation, washed with SSW to remove C O and all traces of NH,' and NO2-, and resuspended in SSW. From this suspension 1 m1 was inoculated into 150 m1 serum bottles containing 124 m1 of NH,'-free medium. Final cell concentration was ca 4 X 105 cells ml-l NH4+ as (NH4)2S04, was added to each bottle to achieve a fi.nal concentration of 10 1tM. Bottles were sealed with silicon rubber stoppers and incubated in the dark on a rotatory shaker (150 rpm) at 25°C for up to 24 h. At different time intervals 25 m1 samples were removed from each bottle and assayed for nitrite production as an index of ammonium oxidation (Bendschnetder & Robinson 1952) Recovery of Nitrobacter sp. from CO was not examined since these organisms were not significantly inhibited by any of the CO concentrat~ons previously tested (Vanzella et al. 1989). Exposure and recovery from light inhibition. Standard inocula of Nitrosomonas cryotolerans and Nitrohacter sp. were inoculated into screw-cap test tubes (25 X 117 mm) which contained 25 m1 of SSW Substrate concentrations were either 0 or 100 pM of NH,+ for the ammonium oxidizer and either 0 or 2 btM of NO2for the nitrite oxidizers. Tubes were incubated in a water bath at 25 "C under a daylight fluorescent light (Philips F30T12/DS/R). The temperature-controlled water bath was a flat-black painted box with circulating distilled water. Light intensity was measured with a LI-COR (model 1800) calibrated radiometer. Irradiance was determined to be ca 25 W m-2 at the surface. Tubes were lying horizontally 1 cm under the water surface in a rack placed in the water bath. Control tubes were wrapped in aluminium foil. In order to compare the effects of sunlight on NH4+ or NO2oxidation, the water bath was placed under full sunlight. Sunlight irradiance was measured to be ca 628 W m-'. After a 2 h exposure, cells were harvested and resuspended as described above. In the case of N~trobacter sp. , recovery studies were done using only sunlight, since artificial light has no cffect (Vanzella et al. 1989).

Recovery of nitrification in marine bacteria following exposure to carbon monoxide or light