Respiratory Electron Transport System Activity Research Articles

The effect of temperature on photosynthetic and respiratory electron transport system activity in the shallow and deep‐living phytoplankton of a subalpine lake

SUMMARY. 1. The influence of temperature on in vivo photosynthetic and in vitro respiratory electron transport system (ETS) activity was determined over the season for the 3 m (warm‐water) and a 20m (cold‐water) phytoplankton communities in Castle Lake. The optimum temperature of photosynthesis at 3 m (X̄=20.8°C) was significantly higher than the average optimum at 20 m (X̄=14.8°C).2. Seasonally, the photosynthetic temperature optimum increased when the blue‐green alga Chroococcus limneticus Lemm. was present. The temperature characteristics of this organism were maintained even after it had settled into the cold water of the hypolimnion.3. Temperature optima were not significantly different in experiments conducted under limiting or saturating photosynthetic photon flux densities (PPFD).4. Short‐term (1 h) preincubations with dissolved inorganic nitrogen (DIN) (≃80 μg NH4NO3‐N l−1) had little effect on the temperature characteristics of photosynthesis while the longer (>24 h) incubations provided by a whole‐lake epilimnetic DIN addition (≃75 μg NH4NO3‐ N l−1) significantly lowered the photosynthetic temperature optimum to 12.5°C. Once this epilimnetic DIN was depleted the optimum roseto25°C, a value higher than that present before the enrichment, which coincided with the growth of C limneticus.5. Respiratory ETS activity usually began to inactivate between 19 and 20°C. However, when C. limneticus was abundant the inactivation temperature was often greater ihan 25°C.6. The average energy of activation (E) and Q10 value for the 3 m community (15.9 kcal mol−1 and 2.6 respectively) were significantly higher than those at 20 m (14.2 kcal mol−1 and 2.4 respectively). Seasonally, the highest E and Q10 values of ETS activity occurred during the late‐summer bloom of C. limneticus.7. These results demonstrate that the epilimnetic and hypolimnetic phytoplankton communities in Castle Lake are physiologically distinct with regards to their temperature characteristics.

Influence of physiological state on indices of respiration rate in protozoa

1. 1. Respiratory electron transport system activity (ETS) was determined in cell-free homogenates of three protozoan species. 2. 2. Protozoa in various physiological states were investigated. 3. 3. Maximum ETS activity was usually associated with maximum rates of growth and intact-cell respiration (R). 4. 4. Some variation in the ETS/R ratio may be attributed to time lags while the macromolecular components of the ETS system are synthesized. In these periods the ratio approaches the theoretical minimum value of unity. 5. 5. The maintenance of a relatively constant ETS/R ratio in most physiological states is characteristic of the larger Protozoa and zooplankton. Variation in the ratio in a small flagellate is typical of most microorganisms.

Respiratory electron transport system activity during larval development of lytechinus variegatus lamarck (echinodermata: echinoidea)

Abstract 1. 1. The rate of energy metabolism increased throughout the larval development of the sea urchin, Lytechinus variegatus. Respiratory electron transport system activity was 2.51 μg—at 0 hr −1 mg protein −1 in the blastula and 4.01 μg—at 0 hr −1 mg protein −1 in the feeding pluteus. 2. 2. Larval protein content increased during this period. 3. 3. The increase in organismal metabolic rate was the result of increased protein-specific ETS activity (probably associated with mitochondrial population increase) and larval growth.

Plankton metabolic activity in the eastern tropical North Pacific

Respiratory electron transport system (ETS) activity of nannoplankton and zooplankton in the euphotic zone was measured at 14 stations in the eastern tropical North Pacific. In addition, ETS activity and zooplankton biomass were measured from the surface to 3000 m at two stations. Respiration rates were calculated from the ETS activities using empirically derived constants. The respiration rates in the euphotic zone, when compared to the regional productivity, indicate that most of the carbon fixed in the euphotic zone was respired there. This was supported by a vertical respiration budget that indicated that 75% of the respiration from 0 to 3000 m occurred within the euphotic zone and > 90% occurred above 200 m. ETS-derived respiration rates in the deep sea (1 to 3 km) were in agreement with rates calculated from temperature, salinity, and oxygen data using a vertical advection-diffusion model.

Seasonal changes in respiratory enzyme activity and productivity in Lake Washington microplankton 1

The seasonal cycle of respiratory electron transport system (ETS) activity, 14C uptake, chlorophyll, temperature, and nutrient concentration in the euphotic zone of Lake Washington during 1974 shows minimum ETS activity (4.2 mg Oeqm−2h−1), 14C uptake (84 mg C m−2d−1), and chlorophyll (10.1 mg m−2) occurred in the first few months of the year and coincided with minimum temperature (≃6.2°C) and maximum nutrient concentrations (PO43− = 250 mg m−2, NO3− = 3.5 g m−2). Maximum ETS activity (109.8 mg Oeqm−2h−1), 14C uptake (2,126 mg C m−2d−1) and chlorophyll (121.7 mg m−2) were observed during the spring bloom. Values were intermediate during the fall period of thermal stratification and nutrient depletion. Respiration rates were calculated from ETS activities and used to calculate production:respiration ratios (P:R). The P:R ratios were low in late summer and fall and high in winter. The percentage of primary production oxidized during a 12‐h dark period varied from >100% to 7%: high percentages in summer, low in late winter.

Respiratory electron transport activity and adenosine triphosphate in the oxygen minimum of the eastern tropical North Pacific

The vertical distribution of respiratory electron transport system (ETS) activity has been determined through the oxygen-deficient zone of the eastern tropical North Pacific. Adenosine triphosphate (ATP) concentration has also determined in the Costa Rica Dome area. There is a distinct, local ETS activity maximum associated with the oxygen minimum but no corresponding ATP increase. It is suggested that the ETS activity maximum results from intracellular biochemical modifications of the ETS system in response to the stress imposed by the low oxygen concentrations, because it is not associated with an increase in ATP biomass. These distributions are also discussed in light of recent suggestions of a mid-depth bacterioplankton maximum.

The effect of hydrostatic pressure on respiratory electron transport system activity in marine zooplankton

The pressure dependence of the respiratory electron transport system (ETS) activity was investigated in four species of zooplankton from Puget Sound and in mixed populations of zooplankton from the eastern tropical North Pacific Ocean. The Puget Sound zooplankton showed no significant pressure effect between 1 and 100 atm, the maximum range of pressure these organisms are likely to encounter in nature. The mixed zooplankton, from both epipelagic and bathypelagic waters, showed no significant pressure effect at 265 atm.

The measurement of respiratory electron-transport-system activity in marine zooplankton

A modification of the tetrazolium reduction method (Packard, 1971) for measurement of respiratory electron transport system activity in marine zooplankton is described. A major modification is the addition of Triton X-100 to the reaction mixture to solubilize formazan produced, thus eliminating an organic extraction step and increasing the sensitivity and versatility of the method. The kinetic parameters of the assay are presented and the apparent effects of Triton X-100 are discussed. The correlation between electron-transport-system (ETS) activity and in vivo respiration (ETS/R) for Calanus pacificus has been found to be 2.02±0.29 (standard deviation). The method is presented as providing a reliable estimate of the zooplankton component of oxygen consumption in the sea.

Modification of the electron transport system (ETS) method for routine measurements of respiratory rates of zooplankton

Respiratory Electron Transport System activity (ETS) was determined in cell-free homogenates of mesozooplankton samples. Several assays were run to investigate possible improvements to the ETS method and to reduce sample processing time. The results showed that: (i) liquid nitrogen is a suitable method for preserving ETS activity for up to at least two months; (ii) the processed sample can be stored for up to 90 minutes in an ice-water bath without loss of activity; (iii) a glass-fibre filter, normally used in phytoplankton assays, is not necessary to achieve efficient enzyme extraction; (iv) centrifugation can be done prior to the assay without any significant loss in activity; and (v) the partitioned enzyme activities were different from the overall ETS activity, with NADH- dehydrogenase activity playing the major role (71 %) and succinate dehydrogenase the minor (<5%). The overall precision of the methods was about 10%, and automation of the method is suggested as a means of standardizing the precision for routine use at sea.