Qu Songsheng

Microcalorimetric study of bacterial growth

Abstract The fundamental growth thermograms of Escherichia coli, Staphylococcus aureus, Salmonella typhosa, Salmonella chaleraeuis and Shigella flexneri have been determined by the microcalorimetric method. These perfect thermogram curves reflect the changes of bacterial growth patterns (including the lag phase of growth, log growth, stationary phase and decline phase of growth). In our experiments, highly characteristic and reproducible growth patterns are observed under the same conditions; therefore, one can use these thermograms as a “finger print” to identify bacteria. Further research on these thermograms has enabled us to calculate the multiplication rate constant and activation energy of bacterial growth. Obviously, these thermogram curves contain ample information which is very significant for studies in microbiological, bio-ther- mokinetic and clinical fields.

Microcalorimetric study of Staphylococcus aureus growth affected by selenium compounds

Abstract The effect of four kinds of the selenium compounds on Staphylococcus aureus growth was studied by microcalorimetry. The extent and duration of the inhibitory effect on the metabolism as judged from the rate constant ( k ), varied with the different drugs. The rate constant of S. aureus (in log phase) in the presence of the drugs decreased with increasing concentrations of the drugs. The experimental results reveal that the sequence of antibiotic activity of selenomorpholines is: N , N′ -methylene bisselenomorpholine>selenomorpholine and Na 2 SeO 3 >selenomorpholine hydrochloride.

A microcalorimetric method for studying the biological effects of La3+ on Escherichia coli

A microcalorimetric technique based on the bacterial heat-output was explored to evaluate the stimulatory effect of La(3+) on Escherichia coli. The power-time curves of the growth metabolism of E. coli and the effect of La(3+) on it were studied using an LKB-2277 BioActivity Monitor, stopped-flow method, at 37 degrees C. For evaluation of the results, the maximum power (P(max)), the growth rate constants (k) and the heat effects (Q(LOG), Q(STAT)) for the log phase, the stationary phase and the total heat effect (Q(T)) for E. coli were determined. The microcalorimetric method agreed with the conventional methods, such as cell numbers and biomass. La(3+) in the concentration ranges of 0-400 microg/ml has stimulatory effects on E. coli, while La(3+) ion of higher concentrations (>400 microg/ml) can inhibit the growth. This phenomenon is very similar to those observed from the in vitro cells and tissues from animals, plants and some microorganisms by other methods.

Study on interaction between T4 phage and Escherichia coli B by microcalorimetric method

The process that T4 phages multiply in host cells of Escherichia coli B was determined using LKB-2277 Bioactivity Monitor by means of stopped-flow method, and the growth was measured turbidometrically at the same time at 37 degrees C. By analyzing thermo-curves, quantitative parameters could be obtained to characterize the interactions of host cells and phages. The parameters such as k(a), P(max), G etc. change regularly with the decrease of multiplicity of infection (MOI) value. Infection-lysis equations were fitted and the lytic rate constant k(L) was obtained. The results show that the metabolic activity of infected cells is more intensive than that of normal cells. The phenomenon of lysis inhibition (LIN) was first detected with the microcalorimetric method, and the mechanism is discussed.

Thermochemical studies of the toxic actions of heavy metal ions on Rhizopus nigricans.

By using a LKB2277 BioActivity Monitor (heat conduction microcalorimeter), stopped-flow method, the thermogenetic curves of Rhizopus nigricans growth at 25 degrees C inhibited by four kinds of heavy metal ions are determined, parameters such as growth rate constants k, inhibitory ratio I, half inhibitory concentration IC50 et al. are obtained. The experimental results show that heavy metal ions can inhibit Rhizopus nigricans growth obviously, low concentration of Cu2+ has promoting action. The inhibitory sequence is Cd2+ > Hg2+ > Pb2+ > Cu2+, half inhibitory concentration of them are Cd+ 0.8 micro g x ml(-1), Hg2+ 1.7 micro g x ml(-1), Pb2+ 48.0 micro g x ml(-1), Cu2+ 110 micro g x ml(-1). This microclorimetric bioassay for acute cellular toxicity is based on metabolic heat evolution from cultured cells. The assay is quantitative, inexpensive, and versatile; moreover, toxicological information can be obtained with cell from other species of interest.

Kinetics of the toxic action of Pb2+ on Rhizopus nigricans as studied by microcalorimetry

The microcalorimetric bioassay for acute cellular toxicity is based on metabolic heat production from cultured cells. Microcalorimetry is a quantitative, inexpensive, and versatile method for measuring acute toxicity. The biological response to toxicants is the inhibition of the heat production rate in cells and toxicity is expressed as the concentration of toxicant that is 50% effective in this inhibition (IC50) In this paper, the effect of Pb2+ on Rhizopus nigricans growth was investigated at 25 degrees C. The relationship between growth rate constants (k) and concentration of Pb2+ (C) is k = 0.04226 exp[-3.636 x 10(-5) (C + 177.0)(2)], and IC50 is 47.5 mu g ml(-1). These signals are readily obtained by an LKB 2277-204 heat conduction microcalorimeter. This system can therefore measure acute toxicity for a broad range of toxicants having target sites in various cellular metabolic pathways

Microcalorimetric investigation of the toxic action of Cd2+ on Rhizopus nigricans growth

The microcalorimetric bioassay for acute cellular toxicity is based on metabolic heat production from cultured cells. Microcalorimetry is a quantitative, inexpensive, and versatile method for toxicology research. The biological response to toxicants is the inhibition of the heat production rate in cells and toxicity is expressed as the concentration of toxicant that is 50% effective in this inhibition (IC(50)). In this paper, the effect of Cd(2+) on Rhizopus nigricans growth was investigated at 25 degrees C. The relationship between growth rate constants (k) and concentration of Cd(2+) (C) shows a logarithmic normal distribution, and described as k=1. 2742x10(61)exp[-1.810x10(-3)(C+283.0)(2)], and IC(50) is 0.72 microg/ml. These signals are readily obtained by an LKB 2277-204 heat conduction microcalorimeter.

Microcalorimetric studies of the toxic action of La3+ in mitochondria isolated from Star-cross 288 chicken heart tissue cells.

The thermogenic curves of the metabolism of mitochondria isolated from the heart of chicken Star-cross 288 and the effect of La3+ on it were studied by using an LKB-2277 BioActivity Monitor, ampoule method, at 37 degrees C. After isolation from the chicken heart tissue, mitochondria still have metabolic activity and can live for a long time by using the stored nutrients. From the thermogenic curves, we obtained the thermokinetic equations under different conditions. The kinetics show that La3+ has changed the metabolism completely.

Microcalorimetric study of mitochondria isolated from fish liver tissue

We determined the thermogenesis curves of mitochondria isolated from fish liver tissue by using an LKB 2277 Bioactivity Monitor. After isolation from the fish liver, mitochondria still have activity and can live for a long time by using the stored nutrients. We calculated the recovery rate constants of mitochondria. We found that the thermogenesis curves of mitochondria are similar to those obtained from prokaryotic cells, but not similar to those obtained from eukaryotic cells. We determined the metabolic thermogenesis curves of mitochondria isolated from two kinds of carp liver tissue, scattered-scaled mirror carp and harvest carp. There are some important similarities and some important differences between these thermogenesis curves.

The effect of the selenomorpholine derivatives on the growth of Staphylococcus aureus studied by microcalorimetry

Abstract The effect of three kinds of the selenomorpholine derivatives on Staphylococcus aureus growth was studied by microcalorimetry. Differences in their capacities to inhibit the metabolism of this bacterium were observed. The growth rate constant, k , of S. aureus (in log phase) in the presence of the drugs decreased with increasing concentrations of the drugs, c . The relationship of k and c is nearly linear for selenium compounds. Judged from the rate constant k and the half-inhibitory concentration, Ic 50 , the experimental results reveal that the sequence of antibiotic activity of selenomorpholines is N -selenomorpholinemethyl succinimide hydrochloride> N -selenomorpholinemethyl succinimide> N -(α-selenomorpholinebenzyl) succinimide