Remarkable micro-endemism and high congeneric richness: eight new cave-restricted species of Pseudochthonius Balzan, 1892 (Pseudoscorpiones, Chthoniidae) from the Brazilian semi-arid

Posted by
  Remarkable micro-endemism and high congeneric richness: eight new cave-restricted species of Pseudochthonius Balzan, 1892 (Pseudoscorpiones, Chthoniidae) from the Brazilian semi-arid Abstract Eight new species of pseudoscorpions belonging to the genus Pseudochthonius Balzan, 1892 are described from the semi-arid region of Brazil. Comprehensive morphological descriptions, diagnostic characters, detailed illustrations, and ecological remarks of the habitats are provided for Pseudochthonius celestialis sp. nov., P. caritas sp. nov., P. patientia sp. nov., P. temperantia sp. nov., P. diligentia sp. nov., P. castitas sp. nov., P. humilitas sp. nov., and P. benignitas sp. nov. In addition, we present a brief discussion of the potential factors underlying the remarkable congeneric species richness observed in this geographically restricted region, as well as the principal threats faced by these species. These findings underscore the importance of conserving caves in order to pr...

Structural determinants of the scorpion venom peptide Uy234 govern bactericidal activity and membrane-disruptive properties

Posted by

 

Image Credit: Urodacus yaschenkoi

Structural determinants of the scorpion venom peptide Uy234 govern bactericidal activity and membrane-disruptive properties

Abstract

Introduction:

The growth-inhibiting effect of the peptide Uy234, present in the venom of the scorpion Urodacus yaschenkoi, has been investigated in two bacterial pathogens: Staphylococcus aureus ATCC 25923 and Acinetobacter baumannii AE12, the latter being a multidrug-resistant clinical isolate. With the aim of determining the possible role of specific residues in the bioactivity of this peptide, we studied a proline residue at position 9 and the C-terminal amidation of this peptide.


Methods:

Two inactivated variants were analyzed: Uy234-C, a non-amidated peptide, and Uy234-A, a P9A mutant. In addition to quantifying in detail the minimum inhibitory and bactericidal concentrations for each microorganism, membrane-damaging effects were assessed through bacterial cell viability assays with SYTO9/PI fluorophores. In addition, AFM, electroforming, and GUV microaspiration were used to determine the effects of each peptide in terms of permeabilization. Molecular dynamics (MD) simulations were also performed for the wild-type peptide and its P9A mutant.


Results:

Only the native peptide Uy234 showed bacteriostatic and bactericidal activity, whereas the P9A mutant and non-amidated variant lost antimicrobial activity, demonstrating the essential role of the Pro-9 residue and C-terminal amidation in Uy234 bioactivity against both pathogens. SYTO9/PI assays in S. aureus infection showed membrane damage only with native Uy234, while AFM and GUV studies revealed membrane thinning, lateral expansion, and dose-dependent permeabilization of lipid bilayers.


Discussion:

Our study provides clear evidence of a damaging effect on the membrane associated with the bioactivity of Uy234. This bioactivity is directly associated with the presence of residue P9 and the presence of C-terminal carboxyamidation. The mutant peptide P9A is unable to permeabilize GUVs, which is consistent with the persistence of a greater degree of structural order, according to MD simulations in the aqueous phase. This study provides a framework for the rational design of bactericidal peptides targeting multidrug-resistant bacteria.


Villa-Merlan AK, Mescola A, Fong-Coronado PA, Juárez González VR, Fernández-Sánchez F, Alessandrini A, Balleza D and Quintero-Hernández V (2026) Structural determinants of the scorpion venom peptide Uy234 govern bactericidal activity and membrane-disruptive properties. Front. Microbiol. 17:1830314. doi: 10.3389/fmicb.2026.1830314