Potential Alkaline Phosphatase Activity Research Articles

Soil alkaline phosphatase activity and bacterial phoD gene abundance and diversity under long-term nitrogen and manure inputs

The impact of long-term inputs of mineral nitrogen (N) fertilizer and swine manure on soil alkaline phosphatase activity is important for phosphorus (P) availability, although its associated gene abundance and diversity within the soil bacterial community are poorly understood. Topsoil (0–10 cm) samples were taken from triplicate field plots that had been maintained under continuous maize (Zea mays) cropping for 28 years with either no nutrient inputs (control), annual inputs of mineral N (urea), swine manure, or combined mineral N-swine manure. Potential alkaline phosphatase activity was determined, together with phoD gene abundance and diversity that using real-time quantitative polymerase chain reaction (PCR) and high-throughput sequencing. Results showed that potential alkaline phosphatase activity and phoD gene abundance were markedly lower in soil from the mineral N treatment compared with the control. On the other hand, long-term swine manure inputs, with and without mineral N, decreased potential alkaline phosphatase activity and phoD gene abundance compared with the control, although concentrations of plant-available P were higher in manure-amended soils. Distinct separation of phoD gene bacterial communities were associated to each fertilization regime, while less pronounced separation was observed between control and mineral N-swine manure treatments. Furthermore, long-term mineral N and swine manure inputs altered the phoD gene community composition. The relative abundance of Bradyrhizobium was higher in mineral N than control soils, and Pseudomonas was less abundant in swine manure than control soils. Our results indicated that long-term application of mineral N in the absence of P inputs significantly reduced potential alkaline phosphatase activity, abundance and community diversity of phoD gene was attributed to a combination of factors, including a 10-fold increase in soil acidity, decreased soil microbial activity, and the apparent inherent stability of organic P in this soil. The findings of this study demonstrated that long-term mineral N inputs adversely impacted the dynamics and bioavailability of P in soil maintained under continuous cropping.

Alkaline phosphatase activity of water column fractions and seagrass in a tropical carbonate estuary, Florida Bay

Few phosphorus-depleted coastal ecosystems have been examined for their ability to hydrolyze phosphomonoesters. We examined seasonal (August 2006–April 2007) alkaline phosphatase activity in Florida Bay, a phosphorus-limited shallow estuary, using fluorescent substrate at low concentrations (≤2.0 μM). In situ dissolved inorganic and organic phosphorus levels and phosphomonoester concentrations were also determined. Water column alkaline phosphatase activity was partitioned into two particulate size fractions (>1.2 and 0.2–1.2 μm) and freely dissolved enzymes (<0.2 μm). Water column alkaline phosphatase activity was also compared to leaf and epiphyte activity of the dominant tropical seagrass Thalassia testudinum. Our results indicate: (1) potential alkaline phosphatase activity in Florida Bay is high compared to other marine ecosystems, resulting in rapid phosphomonoester turnover times (∼2 h). (2) Water column alkaline phosphatase activity dominates, and is split equally between particulate and dissolved fractions. (3) Alkaline phosphatase activity was highest during cyanobacterial blooms, but not when normalized to chl a. These results suggest that dissolved, heterotrophic and autotrophic alkaline phosphatase activity is stimulated by phytoplankton blooms. (4) The dissolved alkaline phosphatase activity is relatively constant, while the particulate activity is seasonally and spatially dynamic, typically associated with phytoplankton blooms. (5) Phosphomonoester concentrations throughout the bay are low, even though potential hydrolysis rates are high. We propose that bioavailable dissolved organic P is hydrolyzed by dissolved and microbial alkaline phosphatase enzymes in Florida Bay. High alkaline phosphatase activity in the bay is also promoted by long hydraulic residence times. This background activity is primarily driven by carbon and phosphorus limitation of microorganisms, and regeneration of enzymes associated with cell lysis. Pulses of inorganic phosphorus and labile organic phosphorus and nitrogen may stimulate autotrophs, particularly cyanobacteria, which in turn promote biological activity that increase alkaline phosphatase activity of both autotrophs and heterotrophs in the bay.

Alkaline phosphatase activity in marine oligotrophic environments: implications of single-substrate addition assays for potential activity estimations

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 277:285-290 (2004) - doi:10.3354/meps277285 Alkaline phosphatase activity in marine oligotrophic environments: implications of single-substrate addition assays for potential activity estimations Marta Sebastián1,*, F. Xavier Niell2 1Centro Oceanográfico de Málaga, Instituto Español de Oceanografía, PO Box 285, Fuengirola, Málaga, Spain 2Departamento de Ecologia, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain *Email: marta.sebastian@ma.ieo.es ABSTRACT: Measurements of potential enzyme activities are usually carried out to compare enzymatic activity between different systems and minimise the effect of product inhibition or substrate depletion during the assay. There is a general practice of estimating potential alkaline phosphatase activity (APA) using single-substrate addition in excess of saturation, as complete kinetic experiments are time-consuming. Here, complete APA kinetic experiments were carried out in the Subtropical North Atlantic Ocean using from 0.1 to 100 µM concentration of the fluorogenic substrate MUF-P. There was a reduction of the velocity of reaction by excess of substrate in all experiments carried out (n = 7). This reduction could be related either to inhibition processes, to quenching effects, or to a loss of fluorescence of the product of reaction due to some kind of biological transformation. Moreover, the substrate concentration above which activity diminished was different between the cases studied. Therefore, there was only a narrow range of concentration in which single-substrate addition experiments would have given results comparable to the maximum enzyme activity, and this range differed between stations. Hence, in order to estimate APA potential activities in marine oligotrophic environments, complete kinetic experiments should be carried out, since the use of single additions in excess of substrate may give erroneous results. This conclusion may be extendable to other commonly performed assays of hydrolytic activities in aquatic environments that also use MUF-substrates. KEY WORDS: Alkaline phosphatase activity · Exoenzyme · Potential assays · Marine environments Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 277. Online publication date: August 16, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Effects of viruses on nutrient turnover and growth efficiency of noninfected marine bacterioplankton

The effects of virus infection and lysis of a marine Vibrio sp. on C, N, and P turnover and the growth efficiency of noninfected bacterioplankton were studied in a series of dilution cultures. The cultures were enriched with various sources of organic matter and N and P. The growth of the Vibrio host and the growth of the natural bacterioplankton were measured by immunofluorescence and 4(prm1),6-diamidino-2-phenylindole staining methods, respectively. Lysis products resulting from infection of the Vibrio sp. caused an increase in metabolic activity and cell production by the noninfected bacterioplankton. In P-limited cultures, the addition of viruses increased the uptake of dissolved organic carbon by 72% and the potential alkaline phosphatase activity by 89% compared with control cultures without viruses. Our data suggest that input of available phosphorus through virus-induced Vibrio lysates occurred, which caused an increase in the bacterial nutrient uptake. The growth efficiency of noninfected bacteria was reduced in the presence of viruses compared with the control without viruses (growth efficiencies, 0.08 (plusmn) 0.03 and 0.24 (plusmn) 0.02, respectively). We suggest that the decrease in growth efficiency may be explained by an increase in bacterial energy demand associated with extracellular degradation of polymeric organic nitrogen and phosphorus in cell lysates.

Nutrient Interactions and Phytoplankton Growth during the Spring Bloom Period in Lake Erken, Sweden

Factorial enrichment experiments with nitrate-N, phosphate-P and selenite-Se, were conducted in situ, with natural phytoplankton assemblages, during two consecutive spring-bloom periods (1983 and 1984) in Lake Erken, Sweden. Nutrient conditions, biomass indicators and algal physiological status, in experiments and in lake water, were compared. Characteristic peaks of phytoplankton, dominated by diatoms, developed in the lake in both years. In 1984, chlorophyll a biomass (30 μgl−1) reached almost twice that of 1983 (17 μgl−1). Inorganic P resources were depleted in both years, but inorganic N was exhausted only in 1984. In 1983, Stephanodiscus hantzschii GRUN v. pusillus GRUN. KRIEGER completely dominated the biomass peak. In 1984, Melosira islandica v. helvetica O. MULL occurred in great numbers along with S. hantzschii v. pusillus. The growth rate of S. hantzschii v. pusillus, surplus phosphorus dynamics and potential alkaline phosphatase activity were different during the two spring periods. In the experiments, eight alternative nutrient situations were tested during four phases of the natural phytoplankton development. The algae responded to enrichments during the entire phytoplankton bloom in 1983 and 1984. Nutrient interactions were important, especially in 1983, and occurred most frequently during the late exponential phase, biomass maximum and declining phase in both years. Interactions between N and P were most common in 1983, occurring during the late exponential phase and biomass maximum. N and Se interaction occurred occasionally. Interactions between P and Se were more frequent in 1983 than in 1984. When nutrients interacted, the combined effect was generally smaller than the sum of their individual effects. P deficiency indicators and the experiments showed clearly that the bloom of 1983 was P limited. In 1984 no such clear pattern was found.

The role of alkaline phosphatase in the sediments of Venice Lagoon on nutrient regeneration

Potential alkaline phosphatase activity and nutrient concentration have been determined in the seawater, interstitial water and sediments of the most polluted area in the Venice Lagoon, at 6 stations, during three cruises performed in the October/November 1982 period, when a minimum phytoplankton standing crop existed. The relationships between parameters were established by linear regression analysis. The results clearly indicate the important role of alkaline phosphatase (APA) in phosphorus regeneration. Indeed, APA appears to be a good indicator of the degree of nutrient regeneration occurring in surface sediments on a global basis. In the Venice Lagoon a significant nutrient release from the sediments to the overlying lagoon water takes place. This process appears to be at least as important as external contributions in both establishing and controlling the concentration of the nutrients in lagoon waters.