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• Metal(loid)s content and mobility were correlated to microbial activities. • Microbial activities are sensitive bioindicators for metal-contaminated sites. • Surface and 1 m deep layers reached alarming and serious pollution levels. • Cadmium and possibly arsenic were the main contributors to the environmental risk. • Modified combined pollution risk was based on chemical and toxicological indices. Abandoned chemical smelting sites containing toxic substances can seriously threaten and pose a risk to the surrounding ecological environment. Soil samples were collected from different depths (0 to 13 m) and analyzed for metal(loid)s content and fractionation, as well as microbial activities. The potential ecological risk indices for the different soil depths (ordered from high to low) were: 1 m (D-1) > surface (S-0) > 5 m (D-5) > 13 m (D-13) > 9 m (D-9), ranging between 1840.65–13,089.62, and representing extremely high environmental risks, of which Cd (and probably not arsenic) contributed to the highest environmental risk. A modified combined pollution risk index (MCR) combining total content and mobile proportion of metal(loid)s, and relative toxicities, was used to evaluate the degree of contamination and potential environmental risks. For the near-surface samples (S-0 and D-1 layers), the MCR considered that As, Cd, Pb, Sb, and Zn achieved high and alarming degrees of contamination, whereas Fe, Mn, and Ti were negligible or low to moderate pollution degrees. Combined microcalorimetry and enzymatic activity measurements of contaminated soil samples were used to assess the microbial metabolic activity characteristics. Correlation analysis elucidated the relationship between metal(loid)s exchangeable fraction or content and microbial activity characteristics (p < 0.05). The microbial metabolic activity in the D-1 layer was low presumably due to heavy metal stress. Enzyme activity indicators and microcalorimetric growth rate (k) measurements were considered sensitive indicators to reflect the soil microbial activities in abandoned chemical smelting sites. [Display omitted] [ABSTRACT FROM AUTHOR]

The combined contamination of nonferrous metal(loid) mining and smelting areas is a global issue, in need of urgent management. To our knowledge, this is the first report of microbial activities by microcalorimetry in specific nonferrous metal(loid) tailings with oligonutrition and high contents of toxic metal(loid)s. Dynamics of bacterial diversity were also characterized. Here we show that tailings had low microbial activities (P max = 64.1–331 μW g−1), which were accelerated by the presence of dipotassium phosphate (P max = 346–856 μW g−1), as measured by microcalorimetry. Frequent detection of S- and metal-resistant related genera and differences of Thiobacillus and Acidithiobacillus abundances indicated that the tailings were in an early stage of acidification. It has been further confirmed by the presence of a weak acid environment and secondary sulfur associated minerals, such as Sb 2 S 3 , FeAsS, FeS 2 , and CuFeS 2. During the acidification process, phosphate, metal(loid)s, and microbial activity were correlated to the bacterial communities. It is suggested that the bacterial communities have metabolic capacities with a high potential for the use in management processes of multi-contaminated nonferrous metalliferous tailings. • Effects of tailing's nonferrous metal(loid)s on microbe. • Microbial activity and diversity were determined by microcalorimetry and sequencing. • The tailings had low basal microbial metabolism capacity. • Abundances of Thiobacillus and Acidithiobacillus suggested the tailings acidification. • Phosphate, metal(loid)s and microbial activity correlated to the bacterial community. [ABSTRACT FROM AUTHOR]

In non-ferrous metal tailings, combined pollution in the surrounding soil is caused by heavy metals and flotation chemicals. The combined effects of nickel (Ni) and its primary ore processing collector, sodium butyl xanthate (SBX), on soil microbial activity were investigated following the fluorescein diacetate hydrolase (FDA) and sucrase (SA) activities, and isothermal microcalorimetry during 60 days. FDA and SA activities as well as overall soil microbial activity were significantly affected by Ni, SBX and Ni/SBX mixture. The inhibition rate ( I ) of the growth rate constant ( k ) being higher with the Ni/SBX mixture than with SBX alone during the experiment. The growth rate constant ( k ) was positively correlated ( p  < 0.05 or p  < 0.01) with enzyme activities (FDA and SA) indicating that k represented a valuable proxy to evaluate the toxic effect of metals and flotation reagents on soil microorganisms. Thus, microcalorimetry was a useful method to characterize soil microbial communities. [ABSTRACT FROM AUTHOR]

Much endeavor has been dispensed recently to evaluate the potential of CO2 mitigation by microalgae. We introduce an alternative, novel, LED-illumination isothermal microcalorimetric method to assess the thermodynamic behaviors of microalgae for better understanding of their carbon sequestration capacity. Microalgae thermodynamic behaviors were recorded as power-time curves, and their indices such as total heat evolution (QT), maximum power output (Pmax) and heat generated by per algae cell (JN/Q) were obtained. The values for highest (74.80 g L−1) and control sample (0.00 g L−1) of QT, Pmax and JN/Q were 20.85 and 2.32 J; 252.17 and 57.67 μW; 7.91 × −06 and 8.80 × −07 J cell−1, respectively. According to the values of QT, a general order to promote the CO2 sequestration was found at 74.8 g L−1 > 29.92 g L−1 > 14.96 g L−1 > 7.48 g L−1 > 0 g L−1 of C sources, which directly corresponded to carbon availability in the growth medium. Chlorella vulgaris GIEC-179 showed the highest peak Pmax at 74.8 g L−1 concentration which was directly transformed to their biomass during bio-fixation of CO2 process. This study is applicable for better understanding of CO2 fixation performance of algae. [ABSTRACT FROM AUTHOR]

The toxicity of five polyaromatic hydrocarbons (PAHs) to metabolism of Escherichia coli ( E. coli ) was evaluated with key parameters, including growth constant (k) and inhibitory ratio ( I) from microcalorimetry analysis. The results showed that the toxicity followed pyrene > 9-phenanthrol > phenanthrene > 3-phenanthrenecarboxylic acid > naphthalene for the chemicals tested. Basing on physical and chemical parameters of these five PAHs, the quantitative structure–activity relationships (QASRs) equation was established by multiple linear regression analysis, indicating that narcosis, a non-specific and non-reactive toxic action, plays the predominant role in toxicity of these five PAHs to bacterial cells. This study illustrates that the toxicity of PAHs are determined by the number of the aromatic ring and the substituent groups, higher toxicity associated with the higher number of the aromatic rings. [ABSTRACT FROM AUTHOR]

In this study, lead-resistant bacterium Arthrobacter sp. GQ-9 with a resistant capability to cadmium, zinc, and copper was isolated from a heavy metal polluted soil. Microcalorimetry analysis was applied to assess the strain’s microbial activity under Pb(II) stress and suggested that GQ-9’s microbial activities under Pb(II) stress were stronger than a non-resistant strain. Biosorption batch experiments revealed that the optimal condition for adsorption of Pb(II) by GQ-9 was pH 5.5, a biomass dosage of 1.2 g L−1, and an initial Pb(II) concentration of 100 mg L−1 with a maximum biosorption capacity of 17.56 mg g−1.Adsorption-desorption experiments and Fourier transform infrared spectroscopy (FTIR) analysis were applied to elucidate the biosorption mechanisms. Adsorption-desorption analysis showed that GQ-9 cells could sequester 56.60% of the adsorbed Pb(II) ions on the cell wall. FTIR analysis suggested that hydroxyl, carboxyl, amino, nitrile, and sulfhydryl groups and amide I, amide II bands on the GQ-9 cell wall participated in the complexation of Pb(II) ions. The present study illustrates that the lead-resistant bacteria GQ-9 has the potential for further development of an effective and ecofriendly adsorbent for heavy metal bioremediation. [ABSTRACT FROM AUTHOR]

In the present study, heavy metal (HM)-tolerant phosphate solubilizing bacteria (PSB) were isolated and their performance during the remediation of Pb and Cd in contaminated soil was studied. A total of 16 bacterial strains and one consortium were isolated, and the consortium had the highest phosphate solubilizing ability and HM tolerance. Great variations between the Fourier transform infrared (FTIR) spectra of consortium cells before and after adsorption of Pb and Cd revealed that amide I/amide II bonds and carboxyl on the cell surface were involved in binding of metal ions. High-throughput sequencing technique revealed that the consortium was composed of Enterobacter spp., Bacillus spp., and Lactococcus spp. The consortium was added into contaminated soil, and its potential ability in dissolution of phosphate from Ca(PO) and subsequent immobilization of HMs was tested. Results showed that when Ca(PO) was applied at 10.60 mg/g soil, PSB addition significantly increased soil available phosphate content from 12.28 to 17.30 mg/kg, thereby enhancing the immobilization rate of Pb and Cd from 69.95 to 80.76% and from 28.38 to 30.81%, respectively. Microcalorimetric analysis revealed that PSB addition significantly improved soil microbial activity, which was possibly related with the decreased HMs availability and the nutrient effect of the solubilized phosphate. The present study can provide a cost-effective and environmental-friendly strategy to remediate multiple HM-contaminated soils. [ABSTRACT FROM AUTHOR]

Flotation reagents are hugely and increasingly used in mining and other industrial and economic activities from which an important part is discharged into the environment. China could be the most affected country by the resulting pollution. However, their ecotoxicological dimension is still less addressed and understood. This study aimed to analyze the toxic effect of sodium isobutyl xanthate (SIBX) and sodium isopropyl xanthate (SIPX) to soil microbial richness and activity and to make a comparison between the two compounds in regard to their effects on soil microbial and enzymes activities. Different methods, including microcalorimetry, viable cell counts, cell density, and catalase and fluorescein diacetate (FDA) hydrololase activities measurement, were applied. The two chemicals exhibited a significant inhibitory effect ( P < 0.05 or P < 0.01) to all parameters, SIPX being more adverse than SIBX. As the doses of SIBX and SIPX increased from 5 to 300 μg g soil, their inhibitory ratio ranged from 4.84 to 45.16 % and from 16.13 to 69.68 %, respectively. All parameters fluctuated with the incubation time (10-day period). FDA hydrolysis was more directly affected but was relatively more resilient than catalase activity. Potential changes of those chemicals in the experimental media and complementarity between experimental techniques were justified. [ABSTRACT FROM AUTHOR]

In this study, a gram-positive fluoranthene-degrading bacterial strain was isolated from crude oil in Dagang Oilfield and identified as Microbacterium paraoxydans JPM1 by the analysis of 16S rDNA sequence. After 25 days of incubation, the strain JPM1 could degrade 91.78 % of the initial amount of fluoranthene. Moreover, four metabolites 9-fluorenone-1-carboxylic acid, 9-fluorenone, phthalic acid, and benzoic acid were detected in the culture solution. The gene sequence encoding the aromatic-ring-hydroxylating dioxygenase was amplified in the strain JPM1 by PCR. Based on the translated protein sequence, a homology modeling method was applied to build the crystal structure of dioxygenase. Subsequently, the interaction mechanism between fluoranthene and the active site of dioxygenase was simulated and analyzed by molecular docking. Consequently, a feasible degrading pathway of fluoranthene in the strain JPM1 was proposed based on the metabolites and the interaction analyses. Additionally, the thermodynamic analysis showed that the strain JPM1 had high tolerance for fluoranthene, and the influence of fluoranthene for the bacterial growth activity was negligible under 100 to 400 mg L concentrations. Taken together, this study indicates that the strain JPM1 has high potential for further study in bioremediation of polycyclic aromatic hydrocarbon (PAH)-contaminated sites. [ABSTRACT FROM AUTHOR]

Hydrocarbon pollution is a worldwide problem. In this study, five surfactants containing SDS, LAS, Brij 30, Tween 80 and biosurfactant were used to evaluate their effect on crude oil biodegradation. Hydrocarbon degrading bacteria were isolated from oil production water. The biosurfactant used was a kind of cyclic lipopeptide produced by Bacillus subtilis strain WU-3. Solubilization test showed all the surfactants could apparently increase the water solubility of crude oil. The microbial adhesion to the hydrocarbon (MATH) test showed surfactants could change cell surface hydrophobicity (CSH) of microbiota, depending on their species and concentrations. Microcalorimetric experiments revealed these surfactants exhibited toxicity to microorganisms at high concentrations (above 1 CMC), except for SDS which showed low antibacterial activity. Surfactant supplementation (about 0.1 and 0.2 CMC) could improve degradation rate of crude oil slightly, while high surfactant concentration (above 1 CMC) may decrease the degradation rate from 50.5% to 28.9%. Those findings of this work could provide guidance for the application of surfactants in bioremediation of oil pollution. [ABSTRACT FROM AUTHOR]

The sulfide mineral flotation collectors are wildly used in China, whereas their toxic effect on soil microbial activity remains largely unexplored. In this study, isothermal microcalorimetric technique and soil enzyme assay techniques were employed to investigate the toxic effect of typical sulfide mineral flotation collectors on soil microbial activity. Soil samples were treated with different concentrations (0-100 μg•g − 1 soil) of butyl xanthate, butyl dithiophosphate, and sodium diethyldithiocarbamate. Results showed a significant adverse effect of butyl xanthate ( p < 0.05), butyl dithiophosphate, and sodium diethyldithiocarbamate ( p < 0.01) on soil microbial activity. The growth rate constants k decreased along with the increase of flotation collectors concentration from 20.0 to 100.0 μg•g. However, the adverse effects of these three floatation collectors showed significant difference. The IC of the investigated flotation reagents followed such an order: IC (butyl xanthate) > IC (sodium diethyldithiocarbamate) > IC (butyl dithiophosphate) with their respective inhibitory concentration as 47.03, 38.36, and 33.34 μg•g. Besides, soil enzyme activities revealed that these three flotation collectors had an obvious effect on fluorescein diacetate hydrolysis (FDA) enzyme and catalase (CAT) enzyme. The proposed methods can provide meaningful toxicological information of flotation reagents to soil microbes in the view of metabolism and biochemistry, which are consistent and correlated to each other. [ABSTRACT FROM AUTHOR]

Carbon dots (Cdots) have a great potential for their widespread biological applications. However, there are a few studies on the biosafety of Cdots. In this work, the biological effect of Cdots on soil microorganism was analyzed by microcalorimetry, soil enzymatic activities, and denaturing gradient gel electrophoresis (DGGE). The addition of Cdots causes a gradual increase of the maximum heat power ( P peak ) and the growth rate ( k ) at low concentration of Cdots (0.0–50.00 μg/g). But there is no significant effect of Cdots on the total heat output ( Q total ). The urease and fluorescein diacetate esterase activities demonstrate that introduction of Cdots to soil has almost no impact on the structure and function of the soil microbial community and microbial processes. The DGGE results exhibit that the control and the Cdots-treated soils display similar patterns, indicating that Cdots have little effect on the microbial community structure. [ABSTRACT FROM AUTHOR]

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are widespread in various ecosystems and are pollutants of great concern due to their potential toxicity, mutagenecity and carcinogenicity. Surfactant has become a hot topic for its wide application in the bioremediation of PAHs. The aim of this work is to explore a microcalorimetric method to determine the toxic effect of pyrene on Bacillus subtilis (B. subtilis) and the PAH-degrading bacteria Burkholderia cepacia (B. cepacia) and to evaluate the effect of Tween 80 on biodegradation of pyrene. Power–time curves were studied and calorimetric parameters including the growth rate constant (k), half inhibitory concentration (IC 50), and total thermal effect (Q T) were determined. B. subtilis, B. cepacia and B. cepacia with Tween 80 were completely inhibited when the concentration of pyrene were 200, 800 and 1600µgmL−1, respectively. B. cepacia shows better tolerance to pyrene than B. subtilis. Tween 80 significantly improves the biodegradation of pyrene by increasing the bioavailability of pyrene. In addition, the expression of catechol 2,3-dioxygenase (C23O) in B. cepacia is responsible for the degradation of pyrene and plays an important role in improving the biodegradation of pyrene. Moreover, the activity of C23O increases with the application of Tween 80. The enhanced bioavailability and biodegradation of pyrene by Tween 80 shows the potential use of Tween 80 in the PAHs bioremediation. [Copyright &y& Elsevier]

Highlights: [•] The acute toxicity of PFOA to P. putida was studied by microcalorimetry. [•] The interaction of PFOA with Cr (III) and TBA was antagonistic. [•] Free NH3 could not be a significant contributor to the observed toxicity of PFOA. [•] A substantial enhancement of the surface pressure of PFOA due to TBA is observed. [•] The higher the surface pressure, the lower the toxicity of PFOA. [Copyright &y& Elsevier]

Large amounts of metal(loid)s in abandoned non-ferrous metal smelting site are released to the surrounding environment, causing serious harm to the environment. A weighted comprehensive pollution risk score (CRS), combining two typical metal(loid)s pollution and risk index evaluation methods (speciation and total content indices), and two microbial activity evaluation methods (microcalorimetry and enzyme activities), is proposed to evaluate the pollution degree and environmental risk of metal(loid)s. In the surface soil (Site SS) of contaminated site, the CRS identified seven metal(loid)s (CRS As (20) > CRS Cd (19) > CRS Sb (18) > CRS Zn (13) = CRS Cu (13) > CRS Ni (10) > CRS Pb (8)) with higher risks, and six (CRS Cr (7) > CRS Mn (4) = CRS V (4) > CRS Al (3) = CRS Mg (3) > CRS Ti (2)) with lower risks. Different areas were sorted by the potential ecological risk index (RI) and CRS index from large to small: the deep soil (Site SD) > Site SS > the surrounding wasteland (Site Y), indicating that smelting site was heavily polluted by metal(loid)s. In Site SS, microbial activities were low confirming the inhibition effect of metal(loid)s on soil microbial community activities. Microbial activity characteristics were correlated to metal(loid)s concentration and mobility, indicating that microbial activity represents a potential indicator of pollution. Particularly, FDA activity and TMA are sensitive indicators to estimate soil metal(loid)s pollution level. Our study provides a comprehensive assessment of the metal(loid)s pollution risk, including microbial activity, in non-ferrous metal smelting sites, useful information for the management and remediation of metal(loid)s polluted sites. [Display omitted] • Smelting area is highly polluted by metal(loid)s. • Comprehensive pollution risk score based on metal(loid)s content and mobility. • As, Cd, Sb, Zn, Cu, Ni and Pb have higher comprehensive pollution risk score. • Contaminated site has lower microbial activity and enzyme activities. • Metal(loid)s content and mobility are correlated to microbial activities. [ABSTRACT FROM AUTHOR]

Highlights: [•] Microbes isolated from crude oil are more tolerant to hexadecane toxicity. [•] IC 50 value of hexadecane on USTB-2 and BSn5 were 375 and 210μgmL−1, respectively. [•] Overexpression of the oxidoreductase genes in the strain USTB-2. [•] Combine chemistry and molecular biology for in situ oil decontamination. [Copyright &y& Elsevier]

The objective of the present study was to evaluate effects of petroleum hydrocarbon contaminated soil on the leguminous plant, Vigna radiata L. Seed germination, metabolism and early growth performance of V. radiata L. were studied as parameters by applying a combined approach. The employed combined method which included microcalorimetry and analysis of the root cross section revealed dose dependent effects of petroleum hydrocarbon contaminated soil on V. radiata L. for most parameters. Although significant reductions in measured parameters were observed even at low total petroleum hydrocarbon (TPH) levels such as 1 % and 1.5 %, calculated inhibitions, IC values and metabolic heat emission-time curves inferred that substantial negative effects can be expected on V. radiata L. in soils with comparatively high contamination levels, such as 2.5 % TPH and higher. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the toxicity effects of benzene (B), toluene (T), ethylbenzene (E), xylene (X) alone and substrate interactions in binary mixtures of BT, BE and BX mixed with equal mass concentrations on facultative anaerobic Rhodococcus sp. ustb-1 in LB medium were examined by a microcalorimetric method. The results showed that T, E and X alone aren''t severely toxic to strain ustb-1 when the concentrations reach 800 μg mg−1, but B alone and these binary mixtures exhibit obvious inhibitory effects on the growth of ustb-1 at the dose of 100 μg mg−1. The toxicity of B in the presence of T and X is not significantly different from B alone, but E increased the toxicity of B. In mineral salt medium, all T and X were removed within 72 h, while complete degradation of B and E did not occur during biodegradation of these binary mixtures. The degradation of B was stimulated in the presence of T and X, but it was inhibited by E. The decreased degradation of B in BE, compared with the degradation of B alone, was attributed to an increase in the toxicity of B in the presence of E. [Copyright &y& Elsevier]

Abstract: The influence of petroleum contamination on soil microbial activities was investigated in 13 soil samples from sites around an injection water well (Iw-1, 2, 3, 4) (total petroleum hydrocarbons (TPH): 7.5–78mgkg−1), an oil production well (Op-1, 2, 3, 4, 5) (TPH: 149-1110mgkg−1), and an oil spill accident well (Os-1, 2, 3, 4) (TPH: 4500–34600mgkg−1). The growth rate constant (μ) of glucose stimulated organisms, determined by microcalorimetry, was higher in Iw soil samples than in Op and Os samples. Total cultivable bacteria and fungi and urease activity also decreased with increasing concentration of TPH. Total heat produced demonstrated that TPH at concentrations less than about 1gkg−1 soil stimulated anaerobic respiration. A positive correlation between TPH and soil organic matter (OM) and stimulation of fungi–bacteria–urease at low TPH doses suggested that TPH is bound to soil OM and slowly metabolized in Iw soils during OM consumption. These methods can be used to evaluate the potential of polluted soils to carry out self-bioremediation by metabolizing TPH. [Copyright &y& Elsevier]

Currently there are very few researches on studying the vertical changes of metabolic and thermodynamic properties of microbial communities in freshwater lake sediment. In this work, a multi-channel microcalorimetric system was applied to investigate both the metabolism and thermodynamic properties of 0-35 cm sediment cores from Lake Honghu (Jingzhou, Hubei Province, China). It is suggested that the catastrophic flood in 1998 had changed the structure of the 20-25 cm sediment layer. In this layer, both the physicochemical properties of sediment and the thermodynamic activities of microorganisms exhibit distinct differences from other layers. It displays the highest TOC, TN and C/N values. The power-time curves of microcalorimetric measurement on the sediment samples were plotted to illustrate their microbial activities. The 20-25 cm sediment layer showed the lowest microbial activities with a maximum heat flow rate of 56.97 μW, a growth rate constant of 0.06 h-1 and the time to reach the peak was 98 h. A positive correlation (r= 0.972, P< 0.001) was found between the cell specific metabolic enthalpy change rate (ΔH0) and the TOC of the sediment samples. ΔH0 could indicate the utilization efficiency of carbon source which is not affected by the biomass but relies on the intrinsic properties of sediment. Our work shows that the higher the TOC in sediment; the lower the efficiency in assimilating carbon into biomass by the microbes. [ABSTRACT FROM AUTHOR]

Abstract: This work investigated the toxicity of two isomeric alkylphthalates, i.e., di-n-octyl phthalate (DOP) and di-2-ethylhexyl phthalate (DEHP) to two model bacteria, Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis), which have been previously used to study the toxicity of environmental pollutants. Microcalorimetry was used as the key analytical tool alongside scanning electron microscopy (SEM) and traditional microbiology techniques. The thermokinetic parameters from microcalorimetry showed that the phthalates had a biphasic effect on the metabolic activities of the bacteria; serving as energy sources for the bacteria thereby stimulating their growth at low dosages (≤150μg/mL), but displaying inhibitory effects at higher dosages (≥300μg/mL), indicated by a sharp decrease in growth rate constants at 450μg/mL. The SEM revealed that the bacterial cells were morphological deformed, with shrunk cells and elongated strands at 600μg/mL of both phthalates. The elongated strands inferred that the phthalates inhibited the reproductive processes of the bacteria by possibly impeding some stages of cell division. The half inhibitory concentrations of the phthalates showed that DEHP was more toxic than DOP. Additionally, E. coli, a facultative anaerobe, was more susceptible to the toxic effects of phthalates than B. subtilis, an obligate aerobe capable of forming endospores crucial for tolerating extreme environmental conditions. [ABSTRACT FROM AUTHOR]

Abstract: The growth of Halobacillus sp. Y35 has been investigated in HGM hypersaline medium with different doses of As(III) and kaolin. The metabolic heat flux decreases with the increase in As(III) concentration, indicating that strain Y35 lowers their metabolic activity in order to resist the As(III) toxicity. Carbon dioxide flux, cell growth and protein synthesis rates, and total thermal effect have been, for the first time, successfully employed simultaneously to assess the effect of As(III) on strain Y35 in the absence and presence of kaolin. The relative adsorption capacity and adsorption intensity of kaolin for As(III) are higher with strain Y35 than that without strain Y35, demonstrating that it is possible to reduce the toxicity of As(III) to our environment by both using mineral adsorption and biosorption technology. Our work shows the potential application of kaolin and strain Y35 for the removal of As(III) from contaminated groundwater. [Copyright &y& Elsevier]

Abstract: Although phenolic compounds are intensively studied for their toxic effects on the environment, the toxicity of catechol, resorcinol and hydroquinone mixtures are still not well understood because most previous bioassays are conducted solely using single compound based on acute tests. In this work, the adverse effect of individual phenolic compounds (catechol, resorcinol and hydroquinone) and the interactive effect of the binary and tertiary mixtures on Bacillus subtilis (B. subtilis) using microcalorimetric method were examined. The toxicity of individual phenolic compounds follows the order catechol>resorcinol>hydroquinone with their respective half inhibitory concentration as 437, 728 and 934µgmL− 1. The power–time curve of B. subtilis growth obtained by microcalorimetry is in complete agreement with the change in turbidity of B. subtilis against time, demonstrating that microcalorimetric method agrees well with the routine microbiological method. The toxicity data obtained from phenolic compound mixtures show that catechol and hydroquinone mixture possess synergistic effect while the other mixtures display additive joint actions. Furthermore, the concentration addition (CA) and independent action (IA) models were employed to predict the toxicities of the phenolic compounds. The experimental results of microcalorimetry show no significant difference on the toxicity of the phenolic compound mixtures from that predicted by CA. However, IA prediction underestimated the mixture effects in all the experiments. [Copyright &y& Elsevier]

Abstract: The inhibitory effects of the pesticide Chlorpyrifos (CPF) and its oxon derivative (CPO) on soil microbial activity were evaluated through the measurement of metabolic parameters and the microbial urease enzyme. The thermodynamic parameters related to microbial activity were measured and recorded as power–time curves. Microbial growth rate constant k, total heat evolution Q T, metabolic enthalpy ΔH met, mass specific heat rate J Q/S, microbial biomass C and inhibitory ratio I were calculated. They showed the linear relationship with doses of CPF and CPO. Thereinto, the linear correlations, k versus biomass C and ΔH met versus biomass C, elucidated that k and ΔH met were growth yield dependent. In this work, 20% inhibitory ratio IC20 was obtained with 9.8μgg−1 for CPF and 0.37μgg−1 CPO, meaning that the acute toxicity of CPO was 26 times that of CPF, since the CPO had more potent toxicity to living organism due to its active functional group. Comparing the change tendency of ΔH met and other parameter, the values almost kept constant when exposure to CPF (<5.0μgg−1). It illustrates that individual reacted to stress resulted from environment change by shifting resources from other biological activities (such as reproduction or growth) toward survival to some extent. Urease activity responses in relation to the CPF and CPO exposure were observed and consistent with above thermodynamic parameters. [Copyright &y& Elsevier]

Abstract: Microcalorimetry was applied to assess and compare the toxic effect of heavy metals, such as As, Cu, Cd, Cr, Co, Pb and Zn, on the soil microbial activities and community. About 1.0g soil spiked 5.0mg glucose and 5.0mg ammonium sulfate, the microbial activities were recorded as power–time curves, and their indices, microbial growth rate constant k, total heat evolution Q T, metabolic enthalpy ΔH met and mass specific heat rate J Q/S , were calculated. Comparing these thermodynamic parameters associated with growth yield, a general order of toxicity to the soil was found to be Cr > Pb > As > Co > Zn > Cd > Cu. When soil was exposed to heavy metals, the amount of bacteria and fungi decreased with the incubation time, and the bacterial number diminished sharply. It illustrates that fungi are more tolerant, and bacteria–fungi ratio would be altered under metal stress. To determine the status of the glucose consumed, a glucose biosensor with eggshell membrane was used to measure the remaining glucose in soil sample. Results showed that the time at which glucose was consumed completely was agreed with the microcalorimetric time to a large extent, and depended on the toxicity of heavy metals as well. [Copyright &y& Elsevier]

Abstract: Zinc (Zn) plays a special role in soil ecology and fertility because it can support the growth of soil organisms or inhibit their growth depending on its concentrations. In this work, the effects of different concentrations of Zn on soil microbial communities and activities were analyzed by loading five different doses of Zn (160–6000μgg−1) into a wheat surface soil. The microbial metabolic process revealed a significant bimodal pattern at high concentrations of Zn (>1920μgg−1). This phenomenon suggested that soil microorganisms were very sensitive to zincous poisoning. A variety of soil quality properties were also measured and assessed. The results showed slower bacterial growth in soil cultures polluted with high levels of Zn. In addition, two kinds of fungi were identified by morphology and glomalin-related soil protein content in the Zn-contaminated soil. The growth of the first kind was inhibited with increase in Zn concentration. By contrast, the second kind could survive and continue to grow with increasing doses of Zn at 160–1920μgg−1 and its growth began to decline with further increase in Zn concentration. Finally, the fungus could not survive at very high (6000μgg−1) Zn concentration. In this work, we conclude that soil microbial communities and activities can adapt to Zn pollution to a certain extent. [Copyright &y& Elsevier]

Microcalorimetric technique based on heat-output measurement, direct microorganism counting and enzymatic activity determination, have been explored to evaluate the toxic effects of diphenol species (catechol, resorcinol, and hydroquinone) on soil microbial activity. The thermokinetic parameters including growth rate constant (k), inhibitory ratio, half inhibitory concentration and total thermal effect (Q total), were calculated and compared using the data obtained from the power–time curves of the microcalorimeter. It was found that addition of high concentrations of diphenol compounds to the soil samples resulted in low microorganism counts. The trend of the number of cultivable microorganisms with increasing concentration of diphenols was similar to specific growth rate k. It appeared that the higher the water soluble carbon (WSC) content, the higher the Q total value. The low dehydrogenase and β-glucosidase found in the soils treated by catechol and hydroquinone was possibly due to their low WSC concentration and high inhibitory effects, respectively. The results reveal the toxicity of the three diphenols in a descending sequence: hydroquinone, resorcinol and catechol. The combination of the three methods is a more comprehensive toxicological investigation of a complex microbiological system. Microcalorimetry is for studying the metabolic growth of microorganisms, the plate counting method is for quantifying the real microbial growth, and the soil enzyme activity is for assessing the intracellular and extracellular activity of microbial biomass. Our proposed methods can provide toxicological information of diphenols to soil microbes from the metabolic, microbial and biochemical point of views which are consistent with and correlated to each other. [Copyright &y& Elsevier]

Solvent tolerance is important because it allows microorganisms to grow at high concentrations of organic solvents. Organisms capable of surviving under these extreme conditions have great application in bioremediation of contaminated sites. In our study, four strains of Pseudomonas sp. B1 and J2, Acinetobacter sp. B2 and J6 which were isolated from the activated sludge were used to evaluate the solvent tolerance by microcalorimetry. The strains B2 and J2 showed high tolerance to organic solvent as they could grow well in the medium containing 10vol% of benzene and 70vol% of toluene, respectively. The higher the growth rate constant, the higher the solvent tolerance of the strains isolated. The microbial growths obtained by microcalorimetry were in good agreement with the results determined by OD600. The decrease in growth rate constant and the change in total thermal effect in the presence of organic solvents were in agreement with the data reported in the literatures. Strains B1 and B2 degraded about 67% and 94% of 0.1vol% benzene within 72h in a medium with benzene as the sole carbon source, respectively. Strains J2 and J6 degraded approximately 92% and 85% of 0.1vol% toluene within 72h, respectively. The related degradation genes detected in previous study in these strains highlight an important potential use of those bacteria for the clean-up of benzene and toluene in the environment. [Copyright &y& Elsevier]

A series of calorimetric experiments were performed to investigate the toxic effects of beta-cypermethrin (BCP), bensulfuron-methyl (BSM) and prometryne (PM) on Pseudomonas putida (P. putida). The metabolic action of P. putida on the three pesticides was studied by obtaining power-time curves. The growth of P. putida was inhibited completely in each case when the concentrations of pesticides were up to 80 μ g mL- 1. The relationships between the inhibitory ratio (k) and doses of contaminants were approximately linear for the three pesticides. The total heat dissipated per milliliter (Qtotal) for the pesticides decreased during the course of the experiment. The OD600 of P. putida growth in the absence and presence of pesticides was also obtained. The power-time curves of P. putida growth coincided with its turbidity curves. This elucidates that microcalorimetric method agrees well with the routine microbiological method. Among these three pesticides, BSM was found to be the most toxic with an IC50 of 19.24 μ g mL- 1 against P. putida. PM exhibited moderate virulence with an IC50 of 27.86 μ g mL- 1 and BCP had the lowest toxicity with an IC50 of 39.64 μ g mL- 1. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the technique of microcalorimetry based on heat-output by aerobic bacterial respiration was explored to evaluate the toxic effect of cadmium on Candida humicola, Bacillus subtilis, singularly or in a mixture of both. Power–time curves of the growth metabolism of C. humicola and B. subtilis and the effect of Cd2+ were studied using the TAM III (the third generation thermal activity monitor) multi-channel microcalorimetric system, isothermal mode, at 28°C. The differences in shape of the power–time curves and the thermodynamic and kinetic characteristics of microorganisms growth were compared. The effect of cadmium added into microorganism would significantly reduce the life cycle and change the thermal effect of microbial metabolic process with different concentrations of Cd2+. The experimental results revealed that at the same concentration, the sequence of inhibitory ratio (I) and maximum thermal power (P max) of the Cd2+ was: mixed microorganisms> C. humicola > B. subtilis. The sequence of total thermal effect (Q total) and growth rate constant (k) is mixed microorganisms> B. subtilis > C. humicola. These results are important to further studies of the physiology and pharmacology of C. humicola and B. subtilis and may support the theory of restoring contaminated soil. [Copyright &y& Elsevier]

Abstract: A series of calorimetric experiments were performed to investigate toxic action of ammonium ferric sulfate (AFS) on Bacillus subtilis, Pseudomonas putida and Candida humicola. The power–time curves of micro-organism metabolism were obtained, and the action of them by addition of AFS was studied. C. humicola, B. subtilis and P. putida were inhibited completely when the concentrations were up to 320.0, 160.0 and 160.0μgmL−1, respectively. The relationships between growth rate constant (k) and doses of AFS were approximately linear for three microbes, P. putida for 10.0–160.0μgmL−1 (R =−0.9746), B. subtilis for 0–160.0μgmL−1 (R =−0.9868) and C. humicola for 10.0–320.0μgmL−1 (R =−0.9955). The total heat dissipated per milliliter (Q T) for three microbes remained balance approximately during the lower doses, P. putida and B. subtilis less than the dose of 20.0μgmL−1, 0.56±0.01 and 0.26±0.01JmL−1, respectively, C. humicola less than the dose of 40.0μgmL−1, 0.58±0.03JmL−1. The biomass and OD600 of three micro-organisms growth in the absence of AFS also were obtained. The power–time curve of C. humicola growth coincided with its turbidity curve. It elucidates that microcalorimetric method agreed with the routine microbiology method. [Copyright &y& Elsevier]

Abstract: A multi-channel thermal activity monitor was applied to study soil microbial activity in Wuhan brown sandy soil in the presence of different concentrations of hexavalent chromium . In order to stimulate the soil microbial activity, 5.0mg of glucose and 5.0mg of ammonium sulfate were added to a 1.20-g soil sample under a controlled humidity of 35%. The results show that the poisonous species of at an half inhibitory concentration value of against soil microbe, and an increase of the amount of hexavalent chromium is associated to a decrease in the microbial activity of the soil, probably due to an increase in the toxicity of hexavalent chromium, affecting strongly the life in this soil microbial environment. Our work also suggests that microcalorimetry is a fast, simple and more sensitive method that can be easily performed to study the toxicity of different species of heavy metals on microorganism compared to other biological methods. [Copyright &y& Elsevier]

A pure culture using aniline as a sole source of carbon and energy was isolated by selective enrichment culturing on a minimum salt medium (MSM) from the Nanjing Chemical Plant, Nanjing, Jiangsu Province, China. An analysis of the 16S rRNA gene sequence and morphological and physiological characteristics showed that this strain was a member of the genus Rhodococcus, and it was designated as strain AN5. Its optimal conditions for aniline biodegradation were 30°C (pH 7.0). Due to the water insolubility of aniline, growth of strain AN5 at various aniline concentrations was studied via spectrophotometry and microcalorimetry in different culture mediums. Strain AN5 not only utilized aniline as its sole carbon and energy resources, but also degraded phenol, benzoic acid and naphthalin. Glucose, peptone and ammonium sulfate, when utilized as its secondary carbon and nitrogen sources, had no active effect on the aniline biodegradation. Such findings would be valuable in the application of strain AN5 to depurate industrial waste water. [ABSTRACT FROM AUTHOR]

A microcalorimetric technique based on bacterial heat output was explored to evaluate the toxic effect of iron species on Escherichia coli. Power-time curves of the growth metabolism of E. coli and the effect of different iron species on it were studied using the TAM III multichannel microcalorimetric system, isothermal mode, at 37°C. The differences in shape of the power-time curves and the thermodynamic and kinetic characteristics of E. coli growth have been compared. The thermodynamic parameters, that is, growth rate constant (k), inhibitory ratio (I), half-inhibitory concentration (IC50), Pmax, and Qtotal, have been calculated. The experimental results reveal that the sequence of antibiotic activity of the different iron species (three forms) on E. coli growth is Fe3+ (ferric citrate) > Fe2+ (ferrous chloride) > Fe3+ (ferric chloride). These results are important to further studies of the physiology and pharmacology of iron species as antibacterial agents. [ABSTRACT FROM AUTHOR]

A set of bimetallic Pt–Ru catalysts prepared by co-impregnation of carbon black with ruthenium(III) chloride hydrate and hydrogen hexachloroplatinate(IV) hydrate were investigated by temperature-programmed reduction (TPR), chemisorption of hydrogen, transmission electron microscopy (TEM), microcalorimetry of adsorbed CO and a structure-sensitive reaction (n-hexane conversion). The results showed that the volumetric capacities for CO and H2 adsorption is influenced in the bimetallic Pt–Ru catalysts by the formation of a Pt–Ru alloy. The n-hexane reaction revealed that the reaction mechanism for the pure Pt catalyst mainly occurs via cyclic isomerization and aromatization due to the presence of bigger Pt surface ensembles, whereas the Pt–Ru catalysts exhibited predominantly bond-shift isomerization by the diluting effect of Ru metal addition. The differential heats of CO chemisorption on Pt–Ru catalysts fell between the two monometallic Pt and Ru catalysts extremes. [Copyright &y& Elsevier]