Rhenium and yttrium ions as antimicrobial agents against multidrug resistant Klebsiella pneumoniae and Acinetobacter baumannii biofilms

© 2019 The Authors. Letters in Applied Microbiology published by John Wiley & Sons Ltd on behalf of Society for Applied Microbiology. Antimicrobial resistance presents major global concerns to patient health. In this study, metal ions of molybdenum, rhenium, yttrium and thallium were tested against bacteria in planktonic and biofilm form using one strain of Klebsiella pneumoniae and Acinetobacter baumannii. The antimicrobial efficacy of the metal ions was evaluated against the planktonic bacterial strains using minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations, whilst the efficacy of the metal ions against biofilms was tested using a crystal violet biofilm assay. Live Dead staining was used to visualize the antimicrobial activity elicited by the metal ions on the bacterial cell. The results showed that higher concentrations of the metals were required to inhibit the growth of biofilms (72·9 mg l −1 to 416·7 mg l −1 ), in comparison to their planktonic counterparts. MICs of the metal ions (<46·9 mg l −1 ) (planktonic cells) did not affect biofilm formation. Overall, rhenium and yttrium were effective antimicrobial agents. Molybdenum demonstrated the greatest level of biotoxicity. When taking into account these results and the known toxicity of thallium, it is possible that rhenium or yttrium ions could be developed as effective biocidal formulations in order to prevent transmission in healthcare environments. Significance and Impact of the Study: The metal ions, molybdenum, rhenium, thallium and yttrium were tested against both Klebsiella pneumoniae and Acinetobacter baumannii in planktonic and biofilm forms. This research demonstrated that all the metal ions may be effective antimicrobial agents. However, molybdenum induced high levels of cytotoxicity, whilst, there was no significant difference in the toxicity of the other metal ions tested. When considering the results for the antimicrobial efficacy and biotoxicity of the metal ions, in conjunction with the known toxicity of thallium in certain chemical compositions, it was concluded that overall rhenium or yttrium ions may be effective antimicrobial agents, one potential application may be utilizing these metal ions in hospital surface cleaning formulations

Middle to Late Quaternary palaeolandscapes of the central Azraq Basin, Jordan: Deciphering discontinuous records of human-environment dynamics at the arid margin of the Levant

The Azraq oasis in the Eastern Desert of Jordan has produced considerable stone artefacts attributed to the early Palaeolithic, yet relatively few data are available regarding the chronology and palaeoenvironmental contexts of the remains. In this study, we present stratigraphic, sedimentological, and micropalaeontological analyses of the Late Acheulean site SM1 located within the former Shishan Marsh, which we combine with geochronological and sedimentological data from 13 neighbouring geological exposures to reconstruct landscape evolution at the western margin of the Shishan Marsh. We then discuss the Late Quaternary palaeolandscapes of the Greater Azraq Oasis Area over the past c. 350 ka. Our work demonstrates that the central Azraq Basin experienced three local wetting-drying cycles since the late Middle Pleistocene that would have dramatically shifted the quantity and distribution of freshwater resources, ranging from expansive wetland landscapes to desert refugia characterised by isolated spring pools—changes that would have significantly impacted the mobility decisions and settlement patterns of Palaeolithic inhabitants. Our study highlights that developing long-term records of human-environment dynamics in arid environments requires a mosaic approach to palaeoenvironmental reconstruction that is nested within a well-developed understanding of landscape evolution

Sphingolipid subtypes differentially control proinsulin processing and systemic glucose homeostasis.

Impaired proinsulin-to-insulin processing in pancreatic β-cells is a key defective step in both type 1 diabetes and type 2 diabetes (T2D) (refs. 1,2), but the mechanisms involved remain to be defined. Altered metabolism of sphingolipids (SLs) has been linked to development of obesity, type 1 diabetes and T2D (refs. 3–8); nonetheless, the role of specific SL species in β-cell function and demise is unclear. Here we define the lipid signature of T2D-associated β-cell failure, including an imbalance of specific very-long-chain SLs and long-chain SLs. β-cell-specific ablation of CerS2, the enzyme necessary for generation of very-long-chain SLs, selectively reduces insulin content, impairs insulin secretion and disturbs systemic glucose tolerance in multiple complementary models. In contrast, ablation of long-chain-SL-synthesizing enzymes has no effect on insulin content. By quantitatively defining the SL–protein interactome, we reveal that CerS2 ablation affects SL binding to several endoplasmic reticulum–Golgi transport proteins, including Tmed2, which we define as an endogenous regulator of the essential proinsulin processing enzyme Pcsk1. Our study uncovers roles for specific SL subtypes and SL-binding proteins in β-cell function and T2D-associated β-cell failure