Dataset Information

A Colorimetric Strategy Based on Aptamer-Catalyzed Hairpin Assembly for the On-Site Detection of Salmonella typhimurium in Milk.

ABSTRACT: Salmonella typhimurium (S. typhimurium) is a foodborne pathogen that has caused numerous outbreaks worldwide, necessitating the development of on-site strategy to prevent early contamination. Here, we set up an enzyme-free strategy for aptamer-catalyzed hairpin assembly in which salt-induced aggregation of unmodified gold nanoparticles (AuNPs) served as a colorimetric signal output, allowing on-site detection of S. typhimurium in milk. The aptamer-functionalized magnetic beads were used as a vehicle of specifically enriching target bacteria which conjugated with target aptamer to trigger the "Y" shape catalytic hairpin assembly (Y-CHA) circuit. Due to the hairpins desorbing from the surface of AuNPs to the formation of a large amount of double-stranded DNA (dsDNA), AuNPs turned from dispersion to aggregation in the presence of S. typhimurium, resulting in a change of the colorimetric signal from red to blue-gray. The signal output showed a linear relationship for S. typhimurium over a concentration range of 102 to 106 CFU/mL, with a sensitivity of 2.4 × 102 CFU/mL under optimal conditions. The visual protocol has excellent selectivity even in the presence of other competitive bacteria and has been validated in real milk samples with a sensitivity of 2.8 × 103 CFU/mL.

SUBMITTER: Chen S

PROVIDER: S-EPMC8623332 | biostudies-literature | 2021 Oct

REPOSITORIES: biostudies-literature

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A Colorimetric Strategy Based on Aptamer-Catalyzed Hairpin Assembly for the On-Site Detection of Salmonella typhimurium in Milk.

Chen Sihan S Zong Xinran X Zheng Jiapeng J Zhang Jiaxin J Zhou Mengyao M Chen Qing Q Man Chaoxin C Jiang Yujun Y

Foods (Basel, Switzerland) 20211022 11

Salmonella typhimurium (S. typhimurium) is a foodborne pathogen that has caused numerous outbreaks worldwide, necessitating the development of on-site strategy to prevent early contamination. Here, we set up an enzyme-free strategy for aptamer-catalyzed hairpin assembly in which salt-induced aggregation of unmodified gold nanoparticles (AuNPs) served as a colorimetric signal output, allowing on-site detection of S. typhimurium in milk. The aptamer-functionalized magnetic bea ...[more]

PMID: 34828820

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Project description:The hook-basal body (HBB) is a key intermediate structure in the flagellar assembly pathway in Salmonella typhimurium. The FlgM protein inhibits the flagellum-specific transcription factor sigma28 in the absence of the intact HBB structure and is secreted out of the cell following HBB completion. The flk gene encodes a positive regulator of the activity of FlgM at an assembly step just prior to HBB completion: at the point of assembly of the P- and L-rings. FlgM inhibition of sigma28-dependent class 3 flagellar gene transcription was relieved in P- and L-ring assembly mutants (flgA, flgH, and flgI) by introduction of a null mutation in the flk gene (J. E. Karlinsey et al., J. Bacteriol. 179:2389-2400, 1997). In P- and L-ring mutant strains, recessive mutations in flk resulted in a reduction in intracellular FlgM levels to those seen in wild-type (Fla+) strains. The reduction in intracellular FlgM levels by mutations in the flk gene was concomitant with a 10-fold increase in transcription of the flgMN operon compared to that of the isogenic flk+ strain, while transcription of the flgAMN operon was unaffected. This was true for both direct measurement of the flgAMN and flgMN mRNA transcripts by RNase T2 protection assays and for lac operon fusions to either the flgAMN or flgMN promoter. Loss of Flk did not allow secretion of FlgM through basal-body structures lacking the P- and L-rings. Intracellular FlgM was stable to proteolysis, and turnover occurred primarily after export out of the cell. Loss of Flk did not result in increased FlgM turnover in either P- or L-ring mutant strains. With lacZ translational fusions to flgM, a null mutation in flk resulted in a significant reduction of flgM-lacZ mRNA translation, expressed from the class 3 flgMN promoter, in P- and L-ring mutant strains. No reduction in either flgAMN or flgMN mRNA stability was measured in the absence of Flk in Fla+, ring mutant, or HBB deletion strains. We conclude that the reduction in the intracellular FlgM levels by mutation in the flk gene is only at the level of flgM mRNA translation.

Dataset Information

A Colorimetric Strategy Based on Aptamer-Catalyzed Hairpin Assembly for the On-Site Detection of Salmonella typhimurium in Milk.

Publications

A Colorimetric Strategy Based on Aptamer-Catalyzed Hairpin Assembly for the On-Site Detection of <i>Salmonella typhimurium</i> in Milk.

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