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Brucellosis is a widespread zoonotic disease caused by Brucella spp. Immunization with attenuated vaccines has proved to be an effective method of prevention; however, it may also interfere with diagnosis. Brucella abortus strain A19, which is homologous to B. abortus strain S19, is widely used for the prevention of bovine brucellosis in China. For effective monitoring of the control of brucellosis, it is essential to distinguish A19 from field strains. Single-nucleotide polymorphism–based assays offer a new approach to such discrimination studies. In the current study, we developed a cycleave PCR assay that successfully distinguished attenuated vaccine strains A19 and S19 from 22 strains of B. abortus and 57 strains of 5 other Brucella species. The assay gave a negative reaction with 4 non- Brucella species. The minimum sensitivity of the assay, evaluated using 10-fold dilutions of chromosomal DNA, was 7.6 fg for the A19 strain and 220 fg for the single non-A19/non-S19 Brucella strain tested ( B. abortus 104M). The assay was also reproducible (intra- and interassay coefficients of variation: 0.003–0.01 and 0.004–0.025, respectively). The cycleave assay gave an A19/S19-specific reaction in 3 out of 125 field serum samples, with the same 3 samples being positive in an alternative A19/S19-specific molecular assay. The cycleave assay gave a total of 102 Brucella-specific reactions (3 being the A19/S19-specific reactions), whereas an alternative Brucella-specific assay gave 92 positive reactions (all also positive in the cycleave assay). Therefore, this assay represents a simple, rapid, sensitive, and specific tool for use in brucellosis control.

Bioelectrochemical system is an emerging technology for the remediation of soils contaminated by petroleum hydrocarbons. However, performance of such systems can be limited by the inefficient mass transport in soil. Here we report a new method of sand amendment, which significantly increases both oxygen and proton transports, resulting to increased soil porosity (from 44.5% to 51.3%), decreased Ohmic resistance (by 46%), and increased charge output (from 2.5 to 3.5Cg(-1)soil). The degradation rates of petroleum hydrocarbons increased by up to 268% in 135d. The degradation of n-alkanes and polycyclic aromatic hydrocarbons with high molecular weight was accelerated, and denaturing gradient gel electrophoresis showed that the microbial community close to the air-cathode was substantially stimulated by the induced current, especially the hydrocarbon degrading bacteria Alcanivorax. The bioelectrochemical stimulation imposed a selective pressure on the microbial community of anodes, including that far from the cathode. These results suggested that sand amendment can be an effective approach for soil conditioning that will enhances the bioelectrochemical removal of hydrocarbons in contaminated soils.

Background Brucellosis is a widespread zoonotic disease caused by Gram-negative Brucella bacteria. Immunisation with attenuated vaccine is an effective method of prevention, but it can interfere with diagnosis. Live, attenuated Brucella abortus strain 104M has been used for the prevention of human brucellosis in China since 1965. However, at present, no fast and reliable method exists that can distinguish this strain from field strains. Single nucleotide polymorphism (SNP)-based assays offer a new approach for such discrimination. SNP-based minor groove binder (MGB) and Cycleave assays have been used for rapid identification of four Brucella vaccine strains (B. abortus strains S19, A19 and RB51, and B. melitensis Rev1). The main objective of this study was to develop a PCR assay for rapid and specific detection of strain 104M. Results We developed a SNP-based MGB PCR assay that could successfully distinguish strain 104M from 18 representative strains of Brucella (B. abortus biovars 1, 2, 3, 4, 5, 6, 7 and 9, B. melitensis biovars 1, 2 and 3, B. suis biovars 1, 2, 3 and 4, B. canis, B. neotomae, and B. ovis), four Brucella vaccine strains (A19, S19, S2, M5), and 55 Brucella clinical field strains. The assay gave a negative reaction with four non-Brucella species (Escherichia coli, Pasteurella multocida, Streptococcus suis and Pseudomonas aeruginosa). The minimum sensitivity of the assay, evaluated using 10-fold dilutions of chromosomal DNA, was 220 fg for the 104M strain and 76 fg for the single non-104M Brucella strain tested (B. abortus A19). The assay was also reproducible (intra- and inter-assay coefficients of variation = 0.006–0.022 and 0.012–0.044, respectively). Conclusions A SNP-based MGB PCR assay was developed that could straightforwardly and unambiguously distinguish B. abortus vaccine strain 104M from non-104M Brucella strains. Compared to the classical isolation and identification approaches of bacteriology, this real-time PCR assay has substantial advantages in terms of simplicity and speed, and also reduces potential exposure to live Brucella. The assay developed is therefore a simple, rapid, sensitive, and specific tool for brucellosis diagnosis and control.

Here, we report a new microbial electrolysis cell (MEC) system for hydrogen generation that was composed of a microbial fuel cell (MFC) and a bio-photoelectrochemical cell (BPEC). The BPEC consisted of a photocathode and a microbially-catalyzed anode. In the new MEC system, hydrogen was produced by the BPEC photocathode when it was illuminated with visible light, with the voltage for electrolysis supplied by the MFC. The electrons produced from the MFC anode were transferred to the BPEC photocathode through an external circuit and then photogenerated holes captured some of the electrons emitted by the MFC anode under visible light. This prevented the recombination of the photogenerated hole and electron pairs, leaving more photogenerated electrons available for hydrogen evolution reactions. This also allowed the remaining electrons from the MFC anode to participate in hydrogen evolution reactions. Under visible light, hydrogen was continuously produced from the new MEC system, with a maximum current density of 0.68 A m−2 and an average hydrogen-production rate of 1.35 ± 0.15 mL h−1.

To enhance the performance of activated carbon air cathodes for microbial fuel cells (MFCs), scattered and dense air-cathodes are fabricated by the rolling-press method with the gas diffusion layer or the catalyst layer (CL) invaded to stainless steel meshes (SSM). The maximum power density with scattered cathodes (2503 ± 61 mW m−2) is 29% higher than those of dense cathodes because of the decreased internal resistance and increased oxygen reduction reaction activity. The decrease in the electrode volume density and invasion of CL into SSM has been demonstrated to be an optimal structure, with the highest exchange current density up to 1.26 A m−2 and the lowest charge transfer resistance as low as 1.5 Ω. The increase in performance is believed to result from the enhanced mass transport through extra pores and the contact of activated carbon to the current collector. This novel structure of an air-cathode has a promising future as an application in MFCs.

Stainless steel mesh (SSM) with four opening sizes (20–80 M) were investigated as matrixes of activated carbon air–cathodes in microbial fuel cells (MFCs). The highest power density of 2151 ± 109 mW m −2 (at 5.54 ± 0.14 A m −2 ) was obtained using 40 M, with a value 45% higher than 1485 ± 18 mW m −2 of 80 M. The trend of linear sweep voltammetries were in accordant with power output over a cathodic potential range from −0.2 to 0 V. The differences in performance were attributed to the internal resistances. Charge transfer resistance ( R ct ) was the dominant internal resistance in most of air–cathodes, with the lowest value of 2 Ω in 40 M. Density of metal mesh exhibited a more significant correlationship with maximum power densities ( R 2 = 0.9222) compared to opening size ( R 2 = 0.7068), demonstrated that the density of metal current collector was vital to the performance of cathodes.

Bioelectrochemical remediation is an emerging technology for in situ removal of petroleum hydrocarbons in soil. Here we demonstrated that the remediation can be extended to a larger range by adding multilayer anodes in contaminated soils. Using a three anodes system with activated carbon as the cathodic catalyst, 918 C of charge transferred during 180 days in aged saline soil. The degradation of both polycyclic aromatic hydrocarbons (PAHs) and n-alkanes were accelerated in each layer compared to the disconnected control. The net degradation rates of total petroleum hydrocarbons, 16 priority PAHs and total n-alkanes (C8–C40) were 18%, 36% and 29%, respectively. Popular exoelectrogens (such as Geobacteraceae sp.) and Escherichia were identified, which possibly played an important role in this bioelectrochemical process.

The extreme salinity and high internal resistance of saline-alkali soil contaminated by petroleum hydrocarbons were two key limitations for using the bioelectrochemical remediation. In order to solve two problems, we simply rinsed soil, added carbon fiber to polluted soil. The charge output was enhanced by 110% with increase of the maximum current densities from 81 to 304 mA·m−2 while hydrocarbons degradation rate enhanced by 484%, especially the high molecular weight fractions (C28–C36 of n-alkanes and 4–6 rings of PAHs). These effects were possibly due to the selective enrichment of species belonged to δ-Proteobacteria (Proteobacteria), Flavobacteriia (Bacteroidetes) or Clostridia (Firmicutes), the activities of biological electron transfer and enzymes. As we know, oxygenase gene that directly decided the process of degradation, was surveyed for the first time in soil bioelectrochemical remediation system. The results confirmed that the bio-current stimulated the activities of naphthalene dioxygenase and xylene monooxygenase and thus the hydrocarbons degradation and the electricity generation. Given that electricity generation and the remediation performance are governed by multiple factors, understanding of microbial community and enzyme gene is crucial to promote the power yield and the bioelectrochemical remediation applicability.

The electrical conductivity (EC) of soil is generally measured after soil extraction, so this method cannot represent the in situ EC of soil (e.g., EC of soils with different moisture contents) and therefore lacks comparability in some cases. Using a resistance measurement apparatus converted from a configuration of soil microbial fuel cell, the in situ soil EC was evaluated according to the Ohmic resistance (Rs) measured using electrochemical impedance spectroscopy. The EC of soils with moisture content from 9.1% to 37.5% was calculated according to Rs. A significant positive correlation (R2 = 0.896, p < 0.01) between the soil EC and the moisture content was observed, which demonstrated the feasibility of the approach. This new method can not only represent the actual soil EC, but also does not need any pretreatment. Thus it may be used widely in the measurement of the EC for soils and sediments.