Hybrid Plasticizers Enhance Specificity and Sensitivity of an Electrochemical-Based Sensor for Cadmium Detection.

In addition to their use as an additive to improve physical properties of solvent polymeric membranes, plasticizers have a considerable impact on the specificity and sensitivity of membrane-modified electrochemical sensors. In this work, we aim at the hybridization of two different plasticizers using the electropolymerization technique in the development of a cadmium(II)-selective electrochemical sensor based on screen-printed gold electrode along with cyclic voltammetric measurement. At this point, we first screen for the primary plasticizer yielding the highest signal using cyclic voltammetry followed by pairing it with the secondary plasticizers giving rise to the most sensitive current response. The results show that the hybridization of DOS and TOTM with 3:1 weight ratio (~137.7-µm-thick membrane) renders a signal that is >26% higher than that from the sensor plasticized by DOS per se in water. The solution of 0.1 mM hydrochloric acid (pH 4) is the optimal supporting electrolyte. In addition, hybrid plasticizers have adequate redox capacity to induce cadmium(II) transfer from bulk solution to the membrane/water interfaces. Conversion of voltammetric signals to semi-integral currents results in linearity with cadmium(II) concentration, indicating the irreversible cadmium(II) transfer to the membrane. The DOS:TOTM hybrid sensor also exhibits high sensitivity, with a limit of detection (LOD) and limit of quantitation (LOQ) of 95 ppb and 288 ppb, respectively, as well as greater specificity towards cadmium(II) than that obtained from the single plasticizer sensor. Furthermore, recovery rates of spiked cadmium(II) in water samples were higher than 97% using the hybrid plasticizer sensor. Unprecedentedly, our work reports that the hybridization of plasticizers serves as ion-to-electron transducer that can improve the sensor performance in cadmium(II) detection.

Genome Sequence of Streptomyces cavourensis BUU135, Isolated from Soil from a Tropical Fruit Farm in Thailand.

Streptomyces cavourensis BUU135 is a bacterial species isolated from the soil of a tropical fruit farm. The genome of S. cavourensis BUU135 comprises a gene encoding nebramycin 5' synthase, which produces nebramycin 5' by catalyzing the O-carbamoylation reaction of tobramycin. The newly sequenced 7.66-Mb draft genome of S. cavourensis BUU135 may contribute to the discovery of novel natural products derived from this organism.

First Draft Genome Sequence of Thermophilic Laceyella tengchongensis BKK01, Isolated from Municipal Solid Waste in Thailand.

Laceyella tengchongensis BKK01 is a thermophilic bacterium isolated from municipal solid waste. The genome of L. tengchongensis BKK01 includes a gene putatively encoding gramicidin S synthase. Gramicidin S has antibiotic activity against some bacteria and fungi. The newly sequenced 3.44-Mb draft genome of L. tengchongensis BKK01 will shed some light on the biosynthesis of gramicidin S.

Draft Genome Sequence of Haloferax volcanii SS0101, Isolated from Salt Farms in Samut Sakhon, Thailand.

Haloferax volcanii SS0101 is a halophilic archaeon isolated from salt farms in Thailand. The genome sequence of H. volcanii SS0101 contains a gene encoding capreomycidine synthase, a key enzyme for capreomycidine biosynthesis. This 3.8-Mb draft genome sequence of H. volcanii SS0101 will provide the tools for investigating genes involved in capeomycidine production in haloarchaea.

A Novel Nucleic Lateral Flow Assay for Screening phaR-Containing Bacillus spp.

Polyhydroxyalkanoate (PHA) synthase is a key enzyme for PHA production in microorganisms. The class IV PHA synthase is composed of two subunits: PhaC and PhaR. The PhaR subunit, which encodes the phaR gene, is only present in class IV PHA synthases. Therefore, the phaR gene is used as a biomarker for bacteria that contain a class IV PHA synthase, such as some Bacillus spp. The phaR gene was developed to screen phaR-containing Bacillus spp. The phaR screening method involved two steps: phaR gene amplification by PCR and phaR amplicon detection using a DNA lateral flow assay. The screening method has a high specificity for phaR-containing Bacillus spp. The lowest amount of genomic DNA of B. thuringiensis ATCC 10792 that the phaR screening method could detect was 10 pg. This novel screening method improves the specificity and sensitivity of phaR gene screening and reduces the time and cost of the screening process, which could enhance the opportunity to discover good candidate PHA producers. Nevertheless, the screening method can certainly be used as a tool to screen phaR-containing Bacillus spp. from environmental samples.

Draft Genome Sequence of Multidrug-Resistant Proteus mirabilis CKTH01, Isolated from Raw Chicken Meat.

Proteus mirabilis CKTH01 is a pathogenic bacterium isolated from raw chicken meat. The genome sequence of P. mirabilis CKTH01 contains genes encoding multidrug efflux pumps, which are the virulence factors of the antibiotic-resistant bacterium. This 3.98-Mb draft genome sequence of P. mirabilis CKTH01 will contribute to the understanding of the distribution of multidrug-resistant P. mirabilis in raw chicken meat at the open markets.

Draft Genome Sequence of Bacillus salarius IM0101, Isolated from Hypersaline Soil in Inner Mongolia, China.

Bacillus salarius IM0101 is a halophilic bacterium that was isolated from soil in Inner Mongolia, China. The genome sequence of B. salarius IM0101 contains a biomarker gene for polyhydroxyalkanoate (PHA) synthesis. This 6.9-Mb draft genome sequence of B. salarius IM0101 will provide new insights into the organism's PHA production machinery.

A novel nucleic lateral flow assay for screening of PHA-producing haloarchaea.

Polyhydroxyalkanoates (PHAs) are important for biodegradable plastic production, and prokaryotes play a very important role in PHA production. PHA synthase is a key enzyme for the polymerization of PHAs. There are four classes of PHA synthase. The phaC gene is necessary for the production of all classes of PHA synthase, whereas the phaE gene is necessary for the production of class III PHA synthase. This gene is a biomarker for microorganisms that contain class III PHA synthase, such as haloarchaea. Standard techniques for screening of PHA-producing haloarchaea require time for culturing and have poor specificity and sensitivity. Thus, the phaE biosensor was developed to overcome these issues. PCR and DNA lateral flow biosensor techniques were combined for construction of the phaE biosensor. The phaE biosensor has a high specificity for PHA-producing haloarchaea. The lowest amount of genomic DNA of Haloquadratum walsbyi DSM 16854 that the phaE gene could be detected by the biosensor was approximately 250 fg. The phaE biosensor can be applied for screening of PHA-producing haloarchaea from environmental samples. The phaE biosensor is easy to handle and dispose. For screening PHA-producing haloarchaea, the phaE biosensor requires less time and costs less than the standard methods.