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A gene homologous to rpoS was cloned from a fatal human pathogen, Vibrio vulnificus. The functional role of rpoS in V. vulnificus was accessed by using an rpoS knockout mutant strain. This mutant was impaired in terms of the ability to survive under oxidative stress, nutrient starvation, UV irradiation, or acidic conditions. The increased susceptibility of the V. vulnificus mutant in the exponential phase to H2O2 was attributed to the reduced activity of hydroperoxidase I (HPI). Although σS synthesis was induced and HPI activity reached the maximal level in the stationary phase, the mutant in the stationary phase showed the same susceptibility to H2O2 as the wild-type strain in the stationary phase. In addition, HPII activity, which is known to be controlled by ers in Escherichia coli, was not detectable in V. vulnificus strains under the conditions tested. The mutant in the exponential phase complemented with multiple copies of either the rpoS or katG gene of V. vulnificus recovered both resistance to H2O2 and HPI activity compared with the control strain. Expression of the katG gene encoding HPI in V. vulnificus was monitored by using a katG::luxAB transcriptional fusion. The expression of this gene was significantly reduced by deletion of ers in both the early exponential and late stationary phases. Thus, σS is necessary for increased synthesis and activity of HPI, and σS is required for exponentially growing V. vulnificus to develop the ability to survive in the presence of H2O2. [ABSTRACT FROM AUTHOR]

Understanding the computational operations involved in conceptual composition is fundamental for theories of language. However, the existing literature on this topic remains fragmented, comprising disconnected theories from various fields. For instance, while formal semantic theories in Linguistics rely on type-driven interpretation without explicitly representing the conceptual content of lexical items, neurolinguistic research suggests that the brain is sensitive to conceptual factors during word composition. What is the relationship between these two types of theories? Do they describe two distinct aspects of composition, operating independently, or do they connect in some way during interpretation by our brain? To probe this, we explored how the mathematical operations explaining the combination of two words into a phrase are affected by the semantic content of items and the formal linguistic relations between the combining items. For six phrase types that varied properties relevant to type-driven interpretation such as modification vs. argument-saturation and modifier context sensitivity, we collected human ratings of experiential semantic features both for the phrases and for all the individual words within the phrases. We then compared the ability of different computational combination rules to explain the phrase ratings based on the individual word ratings. Our results indicate that composition operations are not one-size-fits-all but rather depend on both feature type and linguistic relation. For example, in intersective Adjective-Noun phrases, addition is used to merge attention-related features, while color features are predominantly determined by the first word's ratings. In the case of social features, the verb chiefly guides interpretation in Verb-Noun phrases, whereas in Noun-Noun phrases, the model employs multiplication to combine the social features of the nouns., Competing Interests: Declaration of competing interest The authors declare no competing interest., (Copyright © 2024. Published by Elsevier B.V.)

The Gram-negative opportunistic pathogen, Pseudomonas aeruginosa , has multiple multidrug efflux pumps. MexT, a LysR-type transcriptional regulator, functions as a transcriptional activator of the MexEF-OprN efflux system. MexT consists of an N-terminal DNA-binding domain and a C-terminal regulatory domain (RD). Little is known regarding MexT ligands and its mechanism of activation. We elucidated the crystal structure of the MexT RD at 2.0 Å resolution. The structure comprised two protomer chains in a dimeric arrangement. MexT possessed an arginine-rich region and a hydrophobic patch lined by a variable loop, both of which are putative ligand-binding sites. The three-dimensional structure of MexT provided clues to the interacting ligand structure. A DNase I footprinting assay of full-length MexT identified two MexT-binding sequence in the mexEF oprN promoter. Our findings enhance the understanding of the regulation of MexT-dependent activation of efflux pumps.

The binding of MS2 bacteriophage coat protein (MCP) to MS2 binding site (MBS) RNA stem-loop sequences has been widely used to label mRNA for live-cell imaging at single-molecule resolution. However, concerns have been raised recently from studies with budding yeast showing aberrant mRNA metabolism following the MS2-GFP labeling. To investigate the degradation pattern of MS2-GFP-labeled mRNA in mammalian cells and tissues, we used Northern blot analysis of β-actin mRNA extracted from the Actb-MBS knock-in and MBS×MCP hybrid mouse models. In the immortalized mouse embryonic cell lines and various organ tissues derived from the mouse models, we found no noticeable accumulation of decay products of β-actin mRNA compared with the wild-type mice. Our results suggest that accumulation of MBS RNA decay fragments does not always happen depending on the mRNA species and the model organisms used.