In Situ Enzyme Activity in the Dissolved and Particulate Fraction of the Fluid from Four Pitcher Plant Species of the Genus Nepenthes

The genus Nepenthes, a carnivorous plant, has a pitcher to trap insects and digest them in the contained fluid to gain nutrient. A distinctive character of the pitcher fluid is the digestive enzyme activity that may be derived from plants and dwelling microbes. However, little is known about in situ digestive enzymes in the fluid. Here we examined the pitcher fluid from four species of Nepenthes. High bacterial density was observed within the fluids, ranging from 7×106 to 2.2×108 cells ml−1. We measured the activity of three common enzymes in the fluid: acid phosphatases, β-d-glucosidases, and β-d-glucosaminidases. All the tested enzymes detected in the liquid of all the pitcher species showed activity that considerably exceeded that observed in aquatic environments such as freshwater, seawater, and sediment. Our results indicate that high enzyme activity within a pitcher could assist in the rapid decomposition of prey to maximize efficient nutrient use. In addition, we filtered the fluid to distinguish between dissolved enzyme activity and particle-bound activity. As a result, filtration treatment significantly decreased the activity in all enzymes, while pH value and Nepenthes species did not affect the enzyme activity. It suggested that enzymes bound to bacteria and other organic particles also would significantly contribute to the total enzyme activity of the fluid. Since organic particles are themselves usually colonized by attached and highly active bacteria, it is possible that microbe-derived enzymes also play an important role in nutrient recycling within the fluid and affect the metabolism of the Nepenthes pitcher plant

Bacterial metabolism of algal extracellular carbon

Measurements of microbial utilization of extracellular organic carbon (EOC) released by phytoplankton commonly consider only EOC fractions subject to rapid uptake. Questions remain whether other EOC fractions are metabolized, what portion is labile, and with what assimilation efficiency this carbon substrate is utilized. 14 C-EOC was prepared by incubation of the natural mixed planktonic community from an oligotrophic lake with H 14 CO 3 in the light. 14 C-EOC which was not rapidly removed by heterotrophs remained in solution and was isolated by filtration. This residual EOC was inoculated with lake microheterotrophs in laboratory microcosms, and utilization kinetics were determined through long-term assays of cumulative 14 CO 2 production. Time-courses for 14 CO 2 production were consistent for all assays and were well described by a deterministic mixed-order degradation model. On twelve sampling occasions, from 29% to 76% of residual 14 C-EOC was labile to further metabolism by lake heterotrophs. First-order rate constants for EOC utilization showed a mode of 0.05 to 0.15 per day. From 33% to 78% of gross 14 C-EOC uptake was respired (mean 50%), indicating appreciable return of algal EOC to the pelagic food web as microbial biomass.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42876/1/10750_2004_Article_BF00015524.pd

A method for determining enzymatically hydrolyzable phosphate (EHP) in natural waters

A method for determining enzymatically hydrolyzable phosphate (EHP) in natural waters is described, based on the determination of released inorganic phosphate after the hydrolysis of organophosphoric esters by free, dissolved phosphohydrolases (mainly phosphatase) produced by the biota. The method gives higher values in highly eutrophic waters than the classical procedure of Strickland and Parsons; in samples from less eutrophic habitats the two methods give similar results. The new method is simple, accurate, and can be used in both freshwater and marine studies. It is particularly recommended for determination in hypereutrophic waters, when Pi concentrations exceed 25 µg P liter−1. Representative field data from the euphotic zone of seven lakes and two marine habitats are presented

The use of the photo-elasticity technology of measurements in slope stability monitoring

W artykule zostały opisane możliwości zastosowania technik elastooptycznych do monitoringu dużych obiektów geotechnicznych. Opisano instalację prototypowej geomaty światłowodowej na osuwisku w KWB "Bełchatów" oraz przedstawiono wyniki pomiarów.The article discusses issues connected with possibilities of the use of photo-elasticity technology in large geotechnical objects. It describes the installation of the prototype geotextile with polymer optic fiber on the slope failure in Bełchatów open cast mine and it presents the results of measurements