Urease Activity in Blue-Green Algae

Berns, Donald S.; Holohan, P D; Scott, Edith

doi:10.1126/science.152.3725.1077

Cited by 39 publications

(14 citation statements)

References 9 publications

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“…1 . 5 ) that is soluble and cytoplasmic (Berns et al, 1966;Ge et al, 1990;Mackerras & Smith, 1986;Rai & Singh, 1987;Singh, 1990Singh, , 1991Singh, , 1993. The pH and temperature optima for WH7805 urease are toward the upper and lower ends, respectively, of the range reported for other cyanobacterial ureases ( Table 3).…”

Section: Inactivation Of Urecmentioning

confidence: 85%

The marine cyanobacterium Synechococcus sp. WH7805 requires urease (urea amiohydrolase, EC 3.5.1.5) to utilize urea as a nitrogen source: molecular-genetic and biochemical analysis of the enzyme

Collier¹,

Brahamsha²,

Palenik³

1999

Microbiology

119

101

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Cyanobacteria assigned to the genus Synechococcus are an important component of oligotrophic marine ecosystems, where their growth may be constrained by IOW availability of fixed nitrogen. Urea appears to be a major nitrogen resource in the sea, but little molecular information exists about its utilization by marine organisms, including Synechococcus. Oligonucleotide primers were used to amplify a conserved fragment of the urease (urea amidohydrolase, EC 3.5.1.5) coding region from cyanobacteria. A 5 7 kbp region of the genome of the unicellular marine cyanobacterium Synechococcus sp. strain WH7805 was then cloned, and genes encoding three urease structural subunits and four urease accessory proteins were sequenced and identified by homology. The WH7805 urease had a predicted subunit composition typical of bacterial ureases, but the organization of the WH7805 urease genes was unique. Biochemical characteristics of the WH7805 urease enzyme were consistent with the predictions of the sequence data. Physiological data and sequence analysis both suggested that the urease operon may be nitrogenregulated by the ntcA system in WH7805. Inactivation of the large subunit of urease, ureC, prevented WH7805 and Synechococcus WH8102 from growing on urea, demonstrating that the urease genes cloned are essential to the ability of these cyanobacteria to utilize urea as a nitrogen source.Keywords : nitrogen assimilation, cyanobacterium, ammonium, nitrate, phytoplankton INTRODUCTIONThe unicellular cyanobacteria assigned to the genus Synechococcus (Waterbury & Rippka, 1989) are an important component of the phytoplankton in many marine and freshwater planktonic ecosystems (Fogg, 1987;Waterbury et al., 1986). They contribute most significantly to total primary production in their most oligotrophic habitats (Chisholm, 1992;Fogg, 1987 ; . The GenBank accession numbers for the sequences reported in this paper are AF065139 and AF056189. Joint, 1986), such as those large oceanic regions where nitrogen availability is thought to limit primary productivity. The nitrogen utilized by the cyanobacteria and other primary producers in these regions appears to derive largely from the planktonic food-web-driven recycling of nitrogen from biomass into ammonium and urea (Dugdale 8c Goering, 1967;Fogg, 1987;Hayward, 1991 ;Price & Harrison, 1988). Urea, which is generally present in marine waters at levels of 0-1-1 pM (Antia et al., 1991), is formed by bacterial degradation of nucleic and amino acids and excreted by many animals as a waste product (McCarthy, 1980;Walsh, 1997). Urea is also the single dominant component of the diverse group of organic nitrogenous compounds known collectively as dissolved organic nitrogen that is present in the oligotrophic oceans at a total concentration of about 5 pM (Antia et al., 1991). For all phytoplankton that have been examined except the Chlorophytes, urease is the enzyme responsible for decomposing urea (Leftley & Syrett, 1973). Urease (urea amidohydrolase, EC 3.5.1.5) is a nickel-requiring metalloenzyme ...

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Section: Inactivation Of Urecmentioning

confidence: 85%

The marine cyanobacterium Synechococcus sp. WH7805 requires urease (urea amiohydrolase, EC 3.5.1.5) to utilize urea as a nitrogen source: molecular-genetic and biochemical analysis of the enzyme

Collier¹,

Brahamsha²,

Palenik³

1999

Microbiology

119

101

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“…Rapid release of NH,/NH,+ after addition of urea to T. pseudonana would be anticipated if urease were an extracellular enzyme. Extracellular urease activity has been detected in a higher plant (Murray and Knox 1977), but in a variety of organisms, including phytoplankton, urease seems to be intracellular (Berns et al 1966;Leftley and Syrett 1973;McLean et al 1985). During exponential growth of T. pseudonana in nitrate-replete seawater, 14C-labeled organic products derived from urea C are released into the medium.…”

Section: Methodsmentioning

confidence: 99%

Uptake of urea C and urea N by the coastal marine diatom Thalassiosira pseudonana

Price

Harrison

1988

Limnology & Oceanography

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Urea uptake rates of Thalassiusiru pseudonana (clone 3H) were determined using [14C]urea,[15N]urea, and by measuring disappearance of dissolved urea from the medium after adding 10 lg-atoms urea-N liter-'. In nitrate-sufficient cultures, the average [14C]urea uptake rate was 60% of the urea disappearance rate. Nitrate uptake continued in the presence of urea at a reduced rate, and only 15% of the urea N taken up was retained by the phytoplankton.The increase in PON during incubation was roughly equal to the total NO, and urea N taken up. Average urea uptake rates measured by all methods in 24-h nitrate-starved cultures were in excellent agreement with the rate of increase in PON during a l-h incubation. Uptake rate of [14C]urea and disappearance rate of urea were constant and equal. In neither nitrate-sufficient nor nitrate-starved cultures were [15N]urea uptake rates constant, with maximal rates measured 5.-l 5 min after the addition of urea.Ammonium was released by T. pseudonana following uptake of urea and was then taken up. A model of urea uptake and assimilation by T. pseudonana that involves efflux of urea N as NH, and its rapid reabsorption is proposed. These results can explain previous observations and have implications for utilization and cycling of urea N by phytoplankton in nature.Radioactive ( 14C) and stable (l 5N) isotope tracers of urea are used to measure urea uptake rates of phytoplankton in the laboratory and in nature, but uptake rates determined with these two isotopes are not always equal. Harrison et al. (1985) found that [ 14C]urea uptake rates were greater than [15N]urea uptake rates in the eastern Canadian Arctic, and Price and Harrison (in prep.) obtained similar results for urea uptake by Sargasso Sea plankton. In the Sargasso Sea, the time-courses of uptake of both labeled substrates were also different:[15N]urea incorporation by phytoplankton was roughly constant during a 24-h incubation period, while [ 14C]urea uptake was most rapid over the first 6 h of the incubation. Discrepancy between [14C]urea uptake and the change in the concentration of dissolved urea in seawater has also been re-L Present address: R. M. Parsons Laboratory, Bldg. 48-2 13,

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“…To answer this question, one must first consider the available evidence on the distribution of urea-degrading enzymes in algae and the role of Ni 2+ in the action of these enzymes. In summary, this evidence indicates that (i) two alternative urea-degrading enzymes (urease and ATP-urea amidolyase) occur in algae but only one of them is produced by an individual alga grown on urea, (ii) the urea amidolyase is restricted to some members of the Chlorophyceae with no evidence for its presence in any other algal class, while (iii) urease occurs without exception in members of nine other algal classes examined (Berns et al, 1966;Lui & Roels, 1970;Leftley & Syrett, 1973;Syrett & Leftley, 1976;Bekheet & Syrett, 1977;Carvajal et al, 1982). According to Rees & Bekheet (1982), Ni z+ is required for the synthesis of urease but not for that of the amidolyase, thereby implying that all ureaseproducing algae might be expected to require Ni z+ for growth on urea.…”

Section: Discussionmentioning

confidence: 86%

“…The widespread ability of planktonic mmroalgae to grow photoautotrophically using urea as N-source is now well established (Droop, 1961;McCarthy, 1971;Carpenter, Remsen & Watson, 1972;Antia et al, , 1977Turner, 1979;Neilson & Larsson, 1980;Fisher & Cowdell, 1982), and this nutritional ability has been largely substantiated by determinations of urea uptake (McCarthy, 1972a(McCarthy, , 1972bHealey, 1977;Horrigan & McCarthy, 1981) or the characterization of urea-degrading enzymes in algae (Berns, Holohan & Scott, 1966;Leftley & Syrett, 1973;Syrett & Leftley, 1976;Bekheet & Syrett, 1977;Carvajal, Fernfindez, Rodriguez & Donoso, 1982).…”

mentioning

confidence: 99%

Evidence of nickel ion requirement for autotrophic growth of a marine diatom with urea serving as nitrogen source

Oliveira

Antia²

1984

British Phycological Journal

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Urease Activity in Blue-Green Algae

Abstract: The apparent enzymatic hydrolysis of urea has been detected in whole blue-green algae and in cell extracts. Urease is present as an intracellullar component in cultures in which no bacterial contaminants are found. The activity in the cells was recovered from the extracts.

Cited by 39 publications

References 9 publications

The marine cyanobacterium Synechococcus sp. WH7805 requires urease (urea amiohydrolase, EC 3.5.1.5) to utilize urea as a nitrogen source: molecular-genetic and biochemical analysis of the enzyme

The marine cyanobacterium Synechococcus sp. WH7805 requires urease (urea amiohydrolase, EC 3.5.1.5) to utilize urea as a nitrogen source: molecular-genetic and biochemical analysis of the enzyme

Uptake of urea C and urea N by the coastal marine diatom Thalassiosira pseudonana

Evidence of nickel ion requirement for autotrophic growth of a marine diatom with urea serving as nitrogen source

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