Petrella, S. | bioRxiv Science

bioRxiv2024

New insights into the echinocandin resistance in Candida spp. in the clinical setting

Despite a huge consumption of echinocandins, the emergence of resistance in Candida spp has remained overall limited. Here, we depicted the epidemiology of Candida spp in our center face to the echinocandins consumption. We postulate new hypotheses that may explain the shaping of candines resistance in the clinical setting. Epidemiology of Candida infections and echinocandin consumption were evaluated in our center over 12 years (2006-2018). Glucan synthase genes (fks1, fks2) were sequenced. The in vitro fitness was assessed for couple of isogenic strains, of which one was resistant. Finally, the modelling of Candida FKS proteins was realized. Despite a three-fold increase in echinocandin consumption, no significant emergence of resistance was observed. In Candida albicans, fks1 mutations affect the three-dimensional conformation of the glucan synthase, which may result in altered export of the glucan chain, which could explain the observed reduced fitness. In contrast, cross-complementation between FKS1 and FKS2 in Nakaseomyces glabratus might circumvent the negative impact on fitness. ConclusionsOur results support the fact that N. glabratus is more prone to the spread of echinocandin-resistant strains. The link between mutations in the glucan synthase and fitness of Candida strains might explain the difference in the species-specific emergence of echinocandins-resistant strains.

microbiology↗

bioRxiv2022

A novel nuclease is the executing part of a bacterial plasmid defense system

Cells are continuously facing the risk of taking up foreign DNA that can compromise genomic and cellular integrity. Therefore, bacteria are in a constant arms race with mobile genetic elements such as phages, transposons and plasmids. They have developed several active strategies against invading DNA molecules that can be seen as a bacterial innate immune system. Anti-phage systems are usually organized in defense islands and can consist of restriction-modification (R-M) systems, CRISPR-Cas, and abortive infection (Abi) systems. Despite recent advances in the field, much less is known about plasmid defense systems. We have recently identified the MksBEFG system in Corynebacterium glutamicum as a novel plasmid defense system which comprises homologues of the condensin system MukFEB. Here, we investigated the molecular arrangement of the MksBEFG complex. Importantly, we identified MksG as a novel nuclease that degrades plasmid DNA and is, thus, the executing part of the system. The crystal structure of MksG revealed a dimeric assembly through its DUF2220 C-terminal domains. This domain is homologous to the TOPRIM domain of the topoisomerase II family of enzymes and contains the corresponding divalent ion binding site that is essential for DNA cleavage in topoisomerases, explaining the in vitro nuclease activity of MksG. We further show that the MksBEF subunits exhibit an ATPase cycle similar to MukBEF in vitro and we reason that this reaction cycle, in combination with the nuclease activity provided by MksG, allows for processive degradation of invading plasmids. Super-resolution localization microscopy revealed that the Mks system is spatially regulated via to the polar scaffold protein DivIVA. Introduction of plasmids increases the diffusion rate and alters the localization of MksG, indicating an activation of the system in vivo.

microbiology↗