ABSTRACT
Microbes can modulate ecosystem function since they harbor a vast genetic potential for biogeochemical cycling. The spatial and temporal dynamics of this genetic diversity should be acknowledged to establish a link between ecosystem function and community structure. In this study, we analyzed the genetic diversity of bacterial phosphorus utilization genes in two microbial assemblages, microbialites and bacterioplankton of Lake Alchichica, a semiclosed (i.e., endorheic) system with marked seasonality that varies in nutrient conditions, temperature, dissolved oxygen, and water column stability. We focused on dissolved organic phosphorus (DOP) utilization gene dynamics during contrasting mixing and stratification periods. Bacterial alkaline phosphatases (phoX and phoD) and alkaline beta-propeller phytases (bpp) were surveyed. DOP utilization genes showed different dynamics evidenced by a marked change within an intra-annual period and a differential circadian pattern of expression. Although Lake Alchichica is a semiclosed system, this dynamic turnover of phylotypes (from lake circulation to stratification) points to a different potential of DOP utilization by the microbial communities within periods. DOP utilization gene dynamics was different among genetic markers and among assemblages (microbialite vs. bacterioplankton). As estimated by the system's P mass balance, P inputs and outputs were similar in magnitude (difference was <10 %). A theoretical estimation of water column P monoesters was used to calculate the potential P fraction that can be remineralized on an annual basis. Overall, bacterial groups including Proteobacteria (Alpha and Gamma) and Bacteroidetes seem to be key participants in DOP utilization responses.
Subject(s)
Bacteria/genetics , Genes, Bacterial/genetics , Genetic Variation , Lakes/microbiology , Phosphorus/metabolism , Phylogeny , Alkaline Phosphatase/genetics , Aquatic Organisms/genetics , Aquatic Organisms/metabolism , Bacteria/enzymology , Bacteria/metabolism , Bacteroidetes/genetics , Bacteroidetes/metabolism , Base Sequence , DNA, Bacterial/analysis , Ecosystem , Environment , Gene Expression Regulation, Bacterial , Genetic Markers/genetics , Mexico , Oxygen/chemistry , Phosphorus/chemistry , Phosphorus Compounds/chemistry , Phosphorus Compounds/metabolism , Polymerase Chain Reaction/methods , Proteobacteria/genetics , Proteobacteria/metabolism , RNA, Bacterial/analysis , Seasons , Sequence Analysis , Water/chemistryABSTRACT
This study aimed to evaluate under field conditions the efficiency in the use ofN coated with urease inhibitor in maize. The experiment was conducted in the year of 2007/2008. The experimental design was a randomized block design in a factorial 2 x 6, with five repetitions, constituted the N sources (common and coated with urease inhibitor) and levels (0, 40, 80, 120, 160 and 200 kg ha-1 of N) sidedressing nitrogen application in the growth stage V4. Based on the data obtained were determined recovery efficiencies, utilization, agronomic and physiological N applied. In all cases, the efficiency levels for maize were influenced by levels of sidedressing nitrogen application, in which increasing levels of N resulted in a decrease of the efficiencies, regardless of the source being common urea or coated with urease inhibitor.
Subject(s)
Crops, Agricultural/drug effects , Enzyme Inhibitors/pharmacology , Fertilizers , Nitrogen/pharmacology , Plant Proteins/antagonists & inhibitors , Urease/antagonists & inhibitors , Zea mays/drug effects , Crops, Agricultural/enzymology , Crops, Agricultural/growth & development , Nitrogen/metabolism , Oxides/metabolism , Oxides/pharmacology , Phosphorus Compounds/metabolism , Phosphorus Compounds/pharmacology , Plant Proteins/metabolism , Potassium Compounds/metabolism , Potassium Compounds/pharmacology , Urea/metabolism , Urea/pharmacology , Urease/metabolism , Zea mays/enzymology , Zea mays/growth & developmentABSTRACT
This study was aimed at determining the spatial and temporal variation of P distribution in sediment of an artificial wetland for sewage and industrial wastewater treatment, and the fraction that is potentially involved in the P exchange processes. Influent, effluent, macrophytes and sediment at the inlet, middle and outlet areas were sampled over 24 months. The P-fractionation in sediment was performed following the EDTA method. Eichhornia crassipes and Typha domingensis removed P efficiently when cover was high, but E. crassipes caused anoxic conditions. The increase in cover of T. domingensis may contribute to attain oxic conditions and to improve P removal. When macrophytes are not present or when cover is low, sediment seems to increase removal efficiency. A significant increase in the concentration of the fraction of Fe(OOH) approximately P and mainly that of CaCO(3) approximately P can be observed at the inlet. High pH, Ca(2+) and CO(3)(-)(2) concentrations in the influent suggest that P co-precipitates together with CaCO(3). Therefore, it seems that CaCO(3) approximately P represents the main precipitating mechanism. However, mineralization of organic matter maintained the sediment at a pH range lower than the high values prevailing in the influent. CO(3)(-)(2) could undergo partial dissolution and the released i-P(diss) could be readsorbed onto the Fe(OOH) approximately P fraction. Since the environment for P retention (high pH, Fe, Ca and ionic concentrations) is largely provided by the influent, the wetland may be expected to continue retaining P as far as the composition of the influent is maintained and there are available adsorption sites in the sediment.