GC/MS Method for Positive Detection of Bacillus anthracis Endospores

Integrative Metabolomics and Proteomics Allow the Global Intracellular Characterization of Bacillus subtilis Cells and Spores

Reliable and comprehensive multi-omics analysis is essential for researchers to understand and explore complex biological systems more completely. Bacillus subtilis (B. subtilis) is a model organism for Gram-positive spore-forming bacteria, and in-depth insight into the physiology and molecular basis of spore formation and germination in this organism requires advanced multilayer molecular data sets generated from the same sample. In this study, we evaluated two monophasic methods for polar and nonpolar compound extraction (acetonitrile/methanol/water; isopropanol/water, and 60% ethanol) and two biphasic methods (chloroform/methanol/water, and methyl tert-butyl ether/methanol/water) on coefficients of variation of analytes, identified metabolite composition, and the quality of proteomics profiles. The 60% EtOH protocol proved to be the easiest in sample processing and was more amenable to automation. Collectively, we annotated 505 and 484 metabolites and identified 1665 and 1562 proteins in B. subtilis vegetative cells and spores, respectively. We also show differences between vegetative cells and spores from a multi-omics perspective and demonstrate that an integrative multi-omics analysis can be implemented from one sample using the 60% EtOH protocol. The results obtained by the 60% EtOH protocol provide comprehensive insight into differences in the metabolic and protein makeup of B. subtilis vegetative cells and spores.

The Detection of Anthrax Biomarker DPA by Ratiometric Fluorescence Probe of Carbon Quantum Dots and Europium Hybrid Material Based on Poly(ionic)- Liquid

Bacillus anthracis has gained international attention as a deadly bacterium and a potentially deadly biological warfare agent. Dipicolinic acid (DPA) is the main component of the protective layer of anthracis spores, and is also an anthrax biomarker. Therefore, it is of great significance to explore an efficient and sensitive DPA detection method. Herein, a novel ratio hybrid probe (CQDs-PIL-Eu3+) was prepared by a simple one-step hydrothermal method using carbon quantum dots (CQDs) as an internal reference fluorescence and a covalent bond between CQDs and Eu3+ by using a polyionic liquid (PIL) as a bridge molecule. The ratiometric fluorescence probe was found to have the characteristics of sensitive fluorescence visual sensing in detecting DPA. The structure and the sensing properties of CQDs-PIL-Eu3+ were investigated in detail. In particular, the fluorescence intensity ratio of Eu3+ to CQDs (I616/I440) was linear with the concentration of DPA in the range of 0-50 μM, so the detection limit of the probe was as low as 32 nm, which was far lower than the DPA dose released by the number of anthrax spores in human body (60 μM) and, thus, can achieve sensitive detection. Therefore, the ratiometric fluorescence probe in this work has the characteristics of strong anti-interference, visual sensing, and high sensitivity, which provides a very promising scheme for the realization of anthrax biomarker DPA detection.

A Smartphone Integrated Platform for Ratiometric Fluorescent Sensitive and Selective Determination of Dipicolinic Acid

A desirable lanthanide-based ratiometric fluorescence probe was designed as a multifunctional nanoplatform for the determination of dipicolinic acid (DPA), a unique bacterial endospore biomarker, with high selectivity and sensitivity. The carbon dots (CDs) with blue emission wavelengths at 470 nm are developed with europium ion (Eu³⁺) to form Eu³⁺/CDs fluorescent probes. DPA can specifically combine with Eu³⁺ and then transfer energy from DPA to Eu³⁺ sequentially through the antenna effect, resulting in a distinct increase in the red fluorescence emission peak at 615 nm. The fluorescence intensity ratio of Eu³⁺/CDs (fluorescence intensity at 615 nm/fluorescence intensity at 470 nm) showed good linearity and low detection limit. The developed ratiometric nanoplatform possesses great potential for application in complex matrices owing to its specificity for DPA. In addition, the integration of a smartphone with the Color Picker APP installed enabled point-of-care testing (POCT) with quantitative measurement capabilities, confirming the great potential of the as-prepared measurement platform for on-site testing.

Eu doped Ti3C2 quantum dots to form a ratiometric fluorescence platform for visual and quantitative point-of-care testing of tetracycline derivatives

Antibiotic residues have become a public health issues, the fast detection of tetracycline (Tc) in the environment is urgently required. In this work, Ti₃C₂ quantum dots (Ti₃C₂ QDs) and Europium ions jointly constructed a ratiometric fluorescence (FL) platform for the detection of Tc, based on synergistic impact of the Foster Resonance Energy Transfer (FRET) from Ti₃C₂ QDs to Eu³⁺ ions and the Antenna Effect (AE) between Tc and Eu³⁺ ions. And we proposed a ratiometric FL platform for detecting Tc with good linear response range (100-1000 uM) and low detection limit (48.79 nM). Meanwhile, we applied this platform to detect a serious of β-diketone ligands of Eu³⁺ ions, demonstrating the platform's versatility for this category of chemical. Furthermore, based on the color changes of QDs@Eu³⁺ from blue to red at 365 nm ultraviolet light, an intelligent detection smart device was built for the visual semi-quantitative detection of Tc in actual samples. We proved the applicability of the device in complicated samples and the potential for rapid, sensitive, intuitive and point-of-care detection in the field of environment, food, pharmaceutical and agriculture.

Three novel metal-organic frameworks with different coordination modes for trace detection of anthrax biomarkers

Dipicolinic acid (DPA) is an anthrax biomarker. Its serious consequences make its detection a great need. In this paper, three novel metal-organic frameworks (MOFs) with different coordination modes were synthesized by a simple solvothermal method, which can be used as highly efficient fluorescence sensors for the highly selective and sensitive trace detection of DPA. MOFs 1-3 showed rapid responses to DPA (<30 s), and the limits of detection (LODs) were calculated to be 1.01 × 10^-6 M^-1 (MOF 1), 1.17 × 10^-6 M^-1 (MOF 2) and 2.07 × 10^-6 M^-1 (MOF 3). DPA detection based on MOFs 1-3 in fetal bovine serum is highly reliable based on the high recovery rates (90% to 115%). Hence, the three MOF-based sensors can be used in the real-time detection of DPA.

Multiporous Terbium Phosphonate Coordination Polymer Microspheres as Fluorescent Probes for Trace Anthrax Biomarker Detection

Lanthanide coordination polymers have been recently regarded as attractive sensing materials because of their selectivity, high sensitivity, and rapid response ability. In this research, the multiporous terbium phosphonate coordination polymer microspheres (TbP-CPs) were prepared as a novel fluorescent probe, which showed a fluorescence turn-on response capability for the detection of the trace anthrax biomarker dipicolinate acid (DPA). The morphology and chemical composition of as-prepared TbP-CPs were characterized in detail. The TbP-CPs have the vegetable-flower-like structure and microporous surface. In addition, the as-prepared TbP-CPs not only possess the merits of convenience and simple preparation with high yield but also have the excellent characters as fluorescent probes, such as high stability, good selectivity, and rapid detection ability within 30 s. This proposed sensor could detect DPA with a linear relationship in concentrations ranging from 0 to 8.0 μM and a high detection sensitivity of 5.0 nM. Furthermore, the successful applications of DPA detection in urine and bovine serum were demonstrated. As a result, the recovery ranged from 93.93-101.6%, and the relative standard deviations (RSD) were less than 5%.

Detection of Bacillus anthracis spores by super-paramagnetic lateral-flow immunoassays based on "Road Closure"

Detection of Bacillus anthracis in the field, whether as a natural infection or as a biothreat remains challenging. Here we have developed a new lateral-flow immunochromatographic assay (LFIA) for B. anthracis spore detection based on the fact that conjugates of B. anthracis spores and super-paramagnetic particles labeled with antibodies will block the pores of chromatographic strips and form retention lines on the strips, instead of the conventionally reported test lines and control lines in classic LFIA. As a result, this new LFIA can simultaneously realize optical, magnetic and naked-eye detection by analyzing signals from the retention lines. As few as 500-700 pure B. anthracis spores can be recognized with CV values less than 8.31% within 5 min of chromatography and a total time of 20 min. For powdery sample tests, this LFIA can endure interference from 25% (w/v) milk, 10% (w/v) baking soda and 10% (w/v) starch without any sample pre-treatment, and has a corresponding detection limit of 6×10(4) spores/g milk powder, 2×10(5) spores/g starch and 5×10(5) spores/g baking soda. Compared with existing methods, this new approach is very competitive in terms of sensitivity, specificity, cost and ease of operation. This proof-of-concept study can also be extended for detection of many other large-sized analytes.

Quantitative and sensitive RNA based detection of Bacillus spores

The fast and reliable detection of bacterial spores is of great importance and still remains a challenge. Here we describe a direct RNA-based diagnostic method for the specific detection of viable bacterial spores which does not depends on an enzymatic amplification step and therefore is directly appropriate for quantification. The procedure includes the following steps: (i) heat activation of spores, (ii) germination and enrichment cultivation, (iii) cell lysis, and (iv) analysis of 16S rRNA in crude cell lysates using a sandwich hybridization assay. The sensitivity of the method is dependent on the cultivation time and the detection limit; it is possible to detect 10 spores per ml when the RNA analysis is performed after 6 h of enrichment cultivation. At spore concentrations above 10(6) spores per ml the cultivation time can be shortened to 30 min. Total analysis times are in the range of 2-8 h depending on the spore concentration in samples. The developed procedure is optimized at the example of Bacillus subtilis spores but should be applicable to other organisms. The new method can easily be modified for other target RNAs and is suitable for specific detection of spores from known groups of organisms.