Dual Recognition Strategy for Specific and Sensitive Detection of Bacteria Using Aptamer-Coated Magnetic Beads and Antibiotic-Capped Gold Nanoclusters

Food poisoning and infectious diseases caused by pathogenic bacteria such as Staphylococcus aureus (SA) are serious public health concerns. A method of specific, sensitive, and rapid detection of such bacteria is essential and important. This study presents a strategy that combines aptamer and antibiotic-based dual recognition units with magnetic enrichment and fluorescent detection to achieve specific and sensitive quantification of SA in authentic specimens and in the presence of much higher concentrations of other bacteria. Aptamer-coated magnetic beads (Apt-MB) were employed for specific capture of SA. Vancomycin-stabilized fluorescent gold nanoclusters (AuNCs@Van) were prepared by a simple one-step process and used for sensitive quantification of SA in the range of 32–10⁸ cfu/mL with the detection limit of 16 cfu/mL via a fluorescence intensity measurement. And using this strategy, about 70 cfu/mL of <i>SA</i> in complex samples (containing 3 × 10⁸ cfu/mL of other different contaminated bacteria) could be successfully detected. In comparison to prior studies, the developed strategy here not only simplifies the preparation procedure of the fluorescent probes (AuNCs@Van) to a great extent but also could sensitively quantify SA in the presence of much higher concentrations of other bacteria directly with good accuracy. Moreover, the aptamer and antibiotic used in this strategy are much less expensive and widely available compared to common-used antibodies, making it cost-effective. This general aptamer- and antibiotic-based dual recognition strategy, combined with magnetic enrichment and fluorescent detection of trace bacteria, shows great potential application in monitoring bacterial food contamination and infectious diseases

Dual-Recognition Förster Resonance Energy Transfer Based Platform for One-Step Sensitive Detection of Pathogenic Bacteria Using Fluorescent Vancomycin–Gold Nanoclusters and Aptamer–Gold Nanoparticles

The effective monitoring, identification, and quantification of pathogenic bacteria is essential for addressing serious public health issues. In this study, we present a universal and facile one-step strategy for sensitive and selective detection of pathogenic bacteria using a dual-molecular affinity-based Förster (fluorescence) resonance energy transfer (FRET) platform based on the recognition of bacterial cell walls by antibiotic and aptamer molecules, respectively. As a proof of concept, Vancomycin (Van) and a nucleic acid aptamer were employed in a model dual-recognition scheme for detecting Staphylococcus aureus (Staph. aureus). Within 30 min, by using Van-functionalized gold nanoclusters and aptamer-modified gold nanoparticles as the energy donor and acceptor, respectively, the FRET signal shows a linear variation with the concentration of Staph. aureus in the range from 20 to 10⁸ cfu/mL with a detection limit of 10 cfu/mL. Other nontarget bacteria showed negative results, demonstrating the good specificity of the approach. When employed to assay Staph. aureus in real samples, the dual-recognition FRET strategy showed recoveries from 99.00% to the 109.75% with relative standard derivations (RSDs) less than 4%. This establishes a universal detection platform for sensitive, specific, and simple pathogenic bacteria detection, which could have great impact in the fields of food/public safety monitoring and infectious disease diagnosis

<i>Echinochloa</i> Chloroplast Genomes: Insights into the Evolution and Taxonomic Identification of Two Weedy Species

<div><p>The genus <i>Echinochloa</i> (Poaceae) includes numerous problematic weeds that cause the reduction of crop yield worldwide. To date, DNA sequence information is still limited in the genus <i>Echinochloa</i>. In this study, we completed the entire chloroplast genomes of two <i>Echinochloa</i> species (<i>Echinochloa oryzicola</i> and <i>Echinochloa crus-galli</i>) based on high-throughput sequencing data from their fresh green leaves. The two <i>Echinochloa</i> chloroplast genomes are 139,891 and 139,800 base pairs in length, respectively, and contain 131 protein-coding genes, 79 indels and 466 substitutions helpful for discrimination of the two species. The divergence between the genus <i>Echinochloa</i> and <i>Panicum</i> occurred about 21.6 million years ago, whereas the divergence between <i>E. oryzicola</i> and <i>E. crus-galli</i> chloroplast genes occurred about 3.3 million years ago. The two reported <i>Echinochloa</i> chloroplast genome sequences contribute to better understanding of the diversification of this genus.</p></div

Divergence time of the genus <i>Echinochloa</i>.

<p>Divergence time was estimated using BEAST based on the complete chloroplast genomes of six species (<i>E. oryzicola</i>, <i>E. crus-galli</i>, <i>P. virgatum</i>, <i>S. bicolor</i>, <i>Z. mays</i>, and <i>O. sativa</i>). The numbers showed at nodes indicate divergence time.</p

Phylogenetic relationships among STB03, BTS02, and 30 <i>Echinochloa</i> accessions based on the nucleotide sequences of <i>trn</i>T-L-F region of the chloroplast genome.

<p>See the study by Yamaguchi <i>et al.</i> (2005) for code numbers of the 30 accessions <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0113657#pone.0113657-Aoki1" target="_blank">[12]</a>. The tree was constructed using NJ method. Bootstrap values with less than 50 are not shown.</p

Visualization of alignments of chloroplast genome sequences.

<p>The sequence identity was plotted with the <i>E.oryzicola</i> chloroplast genome as the reference. Sequence identity with 50%–100% is shown. Exonic regions and conserved non-coding sequences (CNS) are colored in blue and red, respectively.</p

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<p>Streptococcus agalactiae and Candida albicans often co-colonize the female genital tract, and under certain conditions induce mucosal inflammation. The role of the interaction between the two organisms in candidal vaginitis is not known. In this study, we found that co-infection with S. agalactiae significantly attenuated the hyphal development of C. albicans, and that EFG1-Hwp1 signal pathway of C. albicans was involved in this process. In a mouse model of vulvovaginal candidiasis (VVC), the fungal burden and the levels of pro-inflammatory cytokines, IL-1β, IL-6 and TNF-α showed a increase on co-infection with S. agalactiae, while the level of TH17 T cells and IL-17 in the cervicovaginal lavage fluid were significantly decreased. Our results indicate that S. agalactiae inhibits C. albicans hyphal development by downregulating the expression of EFG1-Hwp1. The interaction between S. agalactiae and C. albicans may attenuate host vaginal mucosal TH17 immunity and contribute to mucosal colonization by C. albicans.</p

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<p>Streptococcus agalactiae and Candida albicans often co-colonize the female genital tract, and under certain conditions induce mucosal inflammation. The role of the interaction between the two organisms in candidal vaginitis is not known. In this study, we found that co-infection with S. agalactiae significantly attenuated the hyphal development of C. albicans, and that EFG1-Hwp1 signal pathway of C. albicans was involved in this process. In a mouse model of vulvovaginal candidiasis (VVC), the fungal burden and the levels of pro-inflammatory cytokines, IL-1β, IL-6 and TNF-α showed a increase on co-infection with S. agalactiae, while the level of TH17 T cells and IL-17 in the cervicovaginal lavage fluid were significantly decreased. Our results indicate that S. agalactiae inhibits C. albicans hyphal development by downregulating the expression of EFG1-Hwp1. The interaction between S. agalactiae and C. albicans may attenuate host vaginal mucosal TH17 immunity and contribute to mucosal colonization by C. albicans.</p

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<p>Streptococcus agalactiae and Candida albicans often co-colonize the female genital tract, and under certain conditions induce mucosal inflammation. The role of the interaction between the two organisms in candidal vaginitis is not known. In this study, we found that co-infection with S. agalactiae significantly attenuated the hyphal development of C. albicans, and that EFG1-Hwp1 signal pathway of C. albicans was involved in this process. In a mouse model of vulvovaginal candidiasis (VVC), the fungal burden and the levels of pro-inflammatory cytokines, IL-1β, IL-6 and TNF-α showed a increase on co-infection with S. agalactiae, while the level of TH17 T cells and IL-17 in the cervicovaginal lavage fluid were significantly decreased. Our results indicate that S. agalactiae inhibits C. albicans hyphal development by downregulating the expression of EFG1-Hwp1. The interaction between S. agalactiae and C. albicans may attenuate host vaginal mucosal TH17 immunity and contribute to mucosal colonization by C. albicans.</p