HighlightsSeMV RdRp strongly interacts with p10 domain of polyprotein 2a.C-terminal disordered domain of RdRp is required for interaction with p10.p10 acts as a positive regulator of RdRp activity.

No abstract

Reporter phage assays are a promising alternative to culture-based assays for rapidly detecting viable bacteria. The reporter systems used in phage-based detection are typically enzymes and their corresponding substrates that provide a signal following infection and expression. While several reporter systems have been developed, comparing reporter systems based on reported bacteria detection limits from literature can be challenging due to factors other than the reporter system that influence detection capabilities. To advance the development of phage-based assays, a systematic comparison and understanding of the components are necessary. The objective of this study was to directly compare two common enzyme-mediated luminescence reporter systems, NanoLuc/Nano-Glo and alkaline phosphatase (ALP*)/DynaLight, for phage-based detection of bacteria. The detection limits of the purified enzymes were determined, as well as the expression levels and bacteria detection capabilities following engineering of the coding genes into T7 phage and infection of E. coli BL21. When comparing the sensitivity of the purified enzymes, NLuc/Nano-Glo enzyme/substrate system demonstrated a lower detection limit than ALP*/DynaLight. In addition, the expression of the NLuc reporter following phage infection of E. coli was greater than ALP*. The lower detection limit combined with the higher expression resulted in a greater than 100-fold increase in sensitivity for the NLuc/Nano-Glo® reporter system compared to ALP*/DynaLight when used for the detection of E. coli in a model system. These findings provide a comparative analysis of two common reporter systems used for phage-based detection of bacteria and a foundational understanding of these systems for engineering future reporter phage assays.

No abstract

In Vibrio cholerae, the master regulator FlrA controls transcription of downstream flagellar genes in a σ54‐dependent manner. However, the molecular basis of regulation by VcFlrA, which contains a phosphorylation‐deficient N‐terminal FleQ domain, has remained elusive. Our studies on VcFlrA, four of its constructs, and a mutant showed that the AAA+ domain of VcFlrA, with or without the linker ‘L’, remains in ATPase‐deficient monomeric states. By contrast, the FleQ domain plays a pivotal role in promoting higher‐order functional oligomers, providing the required conformation to ‘L’ for ATP/cyclic di‐GMP (c‐di‐GMP) binding. The crystal structure of VcFlrA‐FleQ at 2.0 Å suggests that distinct structural features of VcFlrA‐FleQ presumably assist in inter‐domain packing. VcFlrA at a high concentration forms ATPase‐efficient oligomers when the intracellular c‐di‐GMP level is low. Conversely, excess c‐di‐GMP locks VcFlrA in a non‐functional lower oligomeric state, causing repression of flagellar biosynthesis.