Cupriavidus metallidurans is able to adapt to toxic silver concentrations and previously uncharacterized periplasmic proteins played a crucial role in this adaptation process.

The extensive anthropogenic use of platinum, a rare element found in low natural abundance in the Earth’s continental crust and one of the critical raw materials in the EU innovation partnership framework, has resulted in increased concentrations in surface environments. To minimize its spread and increase its recovery from the environment, biological recovery via different microbial systems is explored. In contrast, studies focusing on the effects of prolonged exposure to Pt are limited. In this study, we used the metal-resistant Cupriavidus metallidurans NA4 strain to explore the adaptation of environmental bacteria to platinum exposure. We used a combined Nanopore–Illumina sequencing approach to fully resolve all six replicons of the C. metallidurans NA4 genome, and compared them with the C. metallidurans CH34 genome, revealing an important role in metal resistance for its chromid rather than its megaplasmids. In addition, we identified the genomic and transcriptomic changes in a laboratory-evolved strain, displaying resistance to 160 µM Pt4+. The latter carried 20 mutations, including a large 69.9 kb deletion in its plasmid pNA4_D (89.6 kb in size), and 226 differentially-expressed genes compared to its parental strain. Many membrane-related processes were affected, including up-regulation of cytochrome c and a lytic transglycosylase, down-regulation of flagellar and pili-related genes, and loss of the pNA4_D conjugative machinery, pointing towards a significant role in the adaptation to platinum.

No abstract

Environmental bacteria belonging to various families were isolated from polluted water collected from ten different sites in Tunisia. Sites were chosen near industrial and urban areas known for their high degree of pollution. The aim of this study was to investigate cross-resistance between heavy metals (HM), i.e., silver, mercury and copper (Ag, Hg, and Cu), and antibiotics. In an initial screening, 80 isolates were selected on ampicillin, and 39 isolates, retained for further analysis, could grow on a Tris-buffered mineral medium with gluconate as carbon source. Isolates were identified based on their 16S rRNA gene sequence. Results showed the prevalence of antibiotic resistance genes, especially all isolates harbored the blaTEM gene. Some of them (15.38%) harbored blaSHV. Moreover, several were even ESBLs and MBLs-producers, which can threaten the human health. On the other hand, 92.30%, 56.41%, and 51.28% of the isolates harbored the heavy metals resistance genes silE, cusA, and merA, respectively. These genes confer resistance to silver, copper, and mercury. A cross-resistance between antibiotics and heavy metals was detected in 97.43% of our isolates.

No abstract

Klebsiella pneumoniae, ubiquitously found in a variety of environmental sources, is an important pathogen in burn wounds and nosocomial infections. Burn wounds have been commonly treated with silver compounds, which are also used in a multitude of (non)medical products. As the latter increased silver discharge into different environments, we evaluated and compared silver resistance in K. pneumoniae isolates collected from patients hospitalized at the Charles‐Nicolle hospital (Tunis, Tunisia) with isolates collected from different metal polluted waters in the north and south of Tunisia. All K. pneumoniae isolates harboured blaTEM‐1 and blaSHV‐1. In addition, all clinical isolates showed a multidrug phenotype and harboured the blaCTX‐M‐15, blaOXA‐1 and blaNDM‐1. Furthermore, all isolates showed resistance to silver nitrate. The silver resistance determinant, screened via the silE gene, was located for all isolates on a large plasmid with a size similar to pMG101. This study showed cross‐resistance between silver and beta‐lactams in clinical as well as environmental K. pneumoniae isolates from Tunisia and showed for the first time that NDM‐1‐producing K. pneumoniae developed resistance to silver.

AimsArbuscular Mycorrhizal Fungi (AMF) are ubiquitous soil microorganisms playing a vital role in the functioning of agricultural ecosystems. Although AMF are generally considered to have a low host specificity, it has been suggested that modern plant breeding has selected crop genotypes that are more selectively associated with AMF, possibly resulting in modern high yielding varieties (HYV) having a lower AMF diversity than traditional crop varieties.Whether this is true for paddy rice varieties under field conditions is not known so far. Here, we aimed at comparing differences of AMF communities among modern HYV and traditional rice varieties. MethodsWe collected root and soil samples of five Bangladeshi rice varieties (two traditional and three modern HYV) from 40 different rice fields and quantified AMF richness, diversity and community composition through high throughput amplicon sequencing of the small subunit (SSU) of the ribosomal RNA cistron. ResultsOverall, 75 AMF OTUs, distributed over six AMF families with Glomeraceae as predominant family were found.After accounting for differences in soil conditions, we found that AMF diversity significantly differed among the five varieties and was higher in the traditional than modern varieties. The composition and structure of the AMF communities were distinct between the traditional and modern varieties. An indicator species analysis detected 9OTUs significantly associated with traditional rice varieties, whereas no indicator OTUs were found for the modern HYV. ConclusionsWe conclude that modern breeding coupled with high fertilizer application rates provide a plausible explanation for the reduced AMF diversity and the different AMF community composition between Bangladeshi modern HYV and traditional varieties.

No abstract