Urea uptake by the marine bacterium Deleya venusta HG1

Abstract

The uptake (transport and metabolism) of urea was studied in a strain of the marine bacterium DeZeya uenusta, measuring the uptake of [14C]urea in viuu and the urease reaction in uitru. Urea uptake in uiuo was sodiumdependent and exhibited a K, value of 1-4 p~ for urea, a broad pH optimum between pH 6.0 and 8-5, a distinct temperature optimum at 35 "C and a requirement for energy. Urease activity in uitru exhibited a K, value of 0.86 mM for urea and showed maximum activities at pH 8.5 and 60 OC; the enzyme was neither dependent on the presence of sodium, nor inhibited by metabolic inhibitors. Synthesis of the urea uptake system was subject to nitrogen control; ammonium resulted in a repression of the system, whereas high uptake rates were observed after growth with nitrate or incubation of the cells in the absence of a nitrogen source. The uptake reaction in uiuu, but not the urease activity in uitru, was decreased greatly in the presence of ammonium. This inhibition was relieved by methionine sulphoximine (MSX), a potent inhibitor of glutamine synthetase; in mutant strains impaired in this enzyme no inhibition of urea uptake by ammonium was observed. These results suggest that glutamine formed from ammonium rather than ammonium itself regulates urea uptake activity in D. uenusta.

Mass coral spawning: A natural large‐scale nutrient addition experiment

“…Recent 15 N tracer experiments in the sediments of a subtropical estuary demonstrated that the microbial community uses both urea and amino acids (labile DON) as well as NO { 3 and NH z 4 as N sources (Veuger et al 2007). Other studies have shown that heterotrophic marine bacteria can assimilate urea (Jahns 1992), mangrove bacteria can assimilate dissolved free amino acids (Stanley et al 1987), and DON is an energy source for benthic respiration, particularly by sulfate reducers (Guldberg et al 2002). In tropical coral reef environments where there is very little freely available DIN, labile DON is probably the major N source for heterotrophic bacteria and the associated DOC may be an additional source of labile carbon for benthic metabolism (Eyre and Ferguson 2005).…”

2‐Methoxy‐3‐(1′‐methylpropyl)pyrazine, pea odour, from the marine bacterium Halomonas venusta

“…Submerged cultures (0.5 l): Halomonas venusta was grown for 65 h at 28°C with 250 ml air/min under magnetic stirring at 500 rpm in: (a) mineral medium 10,11 containing 0.5% glucose with 0.5 M NaCl, Na 2 HPO 4 Ð12 H 2 O (9.0 g/l), KH 2 PO 4 (1.5 g/l), MgSO 4 (0.2 g/l), FeCl 3 (0.0012 g/l), CaCl 2 Ð2 H 2 O (0.02 g/l), NH 4 Cl (1.0 g/l) and 1 ml complex trace elements solution, pH 7. …”

Urea and DON uptake by a Lyngbya gracialis dominated microbial mat: a controlled laboratory experiment

“…The microorganisms responsible for the uptake of urea were not identified. Pure culture studies with cyanobacteria (Healey 1977, Rai & Singh 1987, heterotrophic bacteria (Jahns 1992) and studies of mixed natural populations of cyanobacteria (Takamura et al 1987) have shown that both heterotrophic bacteria and cyanobacteria are able to take up urea. The stimulated urea uptake in the light infers that the process was energy dependent, as previously demonstrated for the heterotrophic marine bacterium Deleya venusta HG1 (Jahns 1992) and several pure cultures of cyanobacteria (Rai & Singh 1987).…”