A modified method for studies of electron transport system activity in freshwater sediments

Abstract

A method for measuring respiratory electron transport system activity (ETSA) in freshwater sediments is presented. It is a modification of the methods used for marine sediments by Christensen & Packard (1977) and OlBnczuk-Neyman & Vosjan (1977). The assay is based on the reduction of the electron acceptor 2-(p iodophenyl) 3 ( p nitrophenyl) 5 phenyl tetrazolium chloride (INT) by cell-free homogenates of sediment samples. This study shows that the method is sensitive, has good accuracy and can be used for freshwater sediments. The accuracy decreases at high turbidity and as yet has only been tested for sediments of the gyttja type. Untreated samples can be stored at low temperature for several weeks without any loss of activity. ETSA decreases with the depth of sediment and with increased amount of allochthonous material in the sediment.

The use of the tetrazolium reduction test for the detection of the terminal electron transport system (ETS) activity in decomposing reed (Phragmites australis /Cav./ Trin. ex Steud.) rhizome

“…Our results suggest that the incubation time should be less than 20 minutes. A similar incubation time (20 minutes) has also been shown for the in vitro measured ETS activity of sediment, phyto-and zooplankton , Owens & King 1975, Kenner & Ahmed 1975, Broberg 1985. However under the low temperature conditions it may be necessary to incubate samples longer until measurable INT-formazan formation occurs.…”

“…A longer homogenization time (4-6 minutes) is necessary to get a cell free enzyme extract from decomposing reed rhizome than from zooplankton, fish spawn (2-3 minutes), and the phytoplankton (3-4 minutes). Phytoplankton and the sediment require a further 20-30-second and a 4-20-minute ultrasonic treatment, respectively (Broberg 1985, G.-Tóth 1993. G.-Tóth (1999) also recommends ultrasonic treatment for the cell free enzyme extraction of heterotrophic nanoflagellata and bacterial colonies.…”

“…Studies of the relationship between in vitro measured ETS-activity and oxygen consumption (R) have shown that ETS-activity can predict the respiration rate of zooplankton, phytoplankton (Kenner & Ahmed, 1975, Owens & King 1975, Devol & Packard 1978, Packard 1985, sediments (Broberg 1985) and bacteria (Christensen et al 1980). The in vitro measured ETS activity of decomposing reed rhizome is a measure of the potential microbial activity.…”

“…The ETS test developed by Packard (1971), Kenner & Ahmed (1975), King (1975), andBroberg (1985), which is widely used to measure in vitro dehydrogenase activity of organisms, was applied with enzyme kinetic experiments on the decomposing reed rhizome. The aim of this work was to develop a quick and easy method to determine the microbial activity and the potential oxygen consumption of microbial decomposers so as to evaluate the relative contributions of microorganisms to litter breakdown, additional studies were also conducted to examine the seasonal changes in microbial activity and the effect of temperature on potential respiratory activity during the decomposition of the reed rhizome.…”

The phosphorus release pathways and their mechanisms driven by organic carbon and nitrogen in sediments of eutrophic shallow lakes

“…In the process of organic matter decomposition, N90% of the biologically consumed O 2 in the biosphere can be occurred (Packard, 1985), which further influenced the electron transport system. DHA measures microbial metabolic activity as respiratory electron transport and has proved to be a good tool for estimating the respiratory potential of sediment (Broberg, 1984;Blenkinsopp and Lock, 1990). Oxidation of organic matter by DHA occurs mostly in organisms that present respiratory chains (Relexans, 1996).…”