Anti-Salmonella type H-z24 Polyclonal antibody

Here we demonstrate a facile and versatile fluorescence resonance energy transfer (FRET) based aptasensor for rapid detection of Salmonella paratyphi A. The assay shows a detection limit up to 10 cfu.mL(-1) with no cross-reactivity with other bacterial species. Less than 8% of inter-assay coefficient variance and recovery rate between 85 and 102% attests the assay reliability. The advantages of FRET-based aptamer assay over the conventional immunoassay formats such as ELISA are the specificity, speed, reliability, and simplicity of the assay. The ssDNA aptamers specific towards pathogenic Salmonella paratyphi A were generated via whole-cell SELEX. The aptamer was conjugated onto quantum dot (QD) that served as the molecular beacon and graphene oxide (GO) was used as a fluorescence quencher. Thus the proposed method enables detection of target pathogen using FRET-based assay. Further interaction of aptamer with pathogen protein DNA gyrase was explored using classical molecular dynamics simulation. (C) 2020 Published by Elsevier B.V.

When a new activity evolves by changes in a pre-existing enzyme this is likely to reduce the original activity, generating a functional trade-off. The properties of this trade-off will affect the continued evolution of both functions. If the trade-off is strong, gene duplication and subsequent divergence would be favored whereas if the trade-off is weak a bi-functional enzyme could evolve that performs both functions. We previously showed that when a bi-functional HisA enzyme was evolved under selection for both HisA and TrpF functions, evolution mainly proceeded via duplication-divergence and specialization, implying that the trade-off is strong between these two functions. Here, we examined this hypothesis by identifying the mutational pathways (i.e., the mutational landscape) in the Salmonella enterica HisA enzyme that conferred a TrpF-like activity, and examining the trade-offs between the original and new activity. For the HisA enzyme there are many different paths toward the new TrpF function, each with its own unique trade-off. A total of 16 single mutations resulted in HisA enzyme variants that acquired TrpF activity and only three of them maintained HisA activity. Twelve mutants were evolved further toward increased TrpF activity and during evolution toward improved TrpF activity the original HisA activity was completely lost in all lineages. We propose that, aside from various relevant ecological factors, two main genetic factors influence whether evolution of a new function proceeds via duplication - divergence (specialization) or by evolution of a generalist: (i) the relative mutation supply of the two pathways and (ii) the shape of the trade-off curve between the native and new function.