Cupriavidus metallidurans is adapted to high concentrations of transition metal cations and is a model system for studying metal homeostasis in difficult environments. The elemental composition of C. metallidurans cells cultivated under various conditions was determined, revealing the ability of the bacterium to shield homeostasis of one essential metal from the toxic action of another. The contribution of metal uptake systems to this ability was studied. C. metallidurans contains three CorA members of the metal inorganic transport (MIT) protein family of putative magnesium uptake systems, ZupT of the ZRT/IRT protein, or ZIP, family, and PitA, which imports metal phosphate complexes. Expression of the genes for all these transporters was regulated by zinc availability, as shown by reporter gene fusions. While expression of zupT was upregulated under conditions of zinc starvation, expression of the other genes was downregulated at high zinc concentrations. Only corA 1 expression was influenced by magnesium starvation. Deletion mutants were constructed to characterize the contribution of each system to transition metal import. This identified ZupT as the main zinc uptake system under conditions of low zinc availability, CorA 1 as the main secondary magnesium uptake system, and CorA 2 and CorA 3 as backup systems for metal cation import. PitA may function as a cation-phosphate uptake system, the main supplier of divalent metal cations and phosphate in phosphate-rich environments. Thus, metal homeostasis in C. metallidurans is achieved by highly redundant metal uptake systems, which have only minimal cation selectivity and are in combination with efflux systems that "worry later" about surplus cations.Sophisticated cellular biochemistry needs metals as cofactors. About 40% of all enzymes have them, ranking from Mg (16%) Ͼ Zn (9%) Ͼ Fe (8%) Ͼ Mn (6%) Ͼ Ca (2%) Ͼ Co and Cu (1%) down to K, Na, Ni, V, Mo, W, and only one example of Cd (59). It is an interesting question how the correct metal is allocated to the right protein, a challenge especially for the divalent metal cations Mg 2ϩ , Zn 2ϩ , Fe 2ϩ , Mn 2ϩ , Co 2ϩ , Ni 2ϩ , and Cu 2ϩ . These metals compete with each other for the metal binding sites in enzymes (16). Additionally, Fe 2ϩ/3ϩ and Cu ϩ/2ϩ promote dangerous reactive oxygen species in Fenton and Fenton-like reactions, as described by Haber and Weiss (13).Part of the solution to this problem might be to keep the metal cation bouquet in any cellular compartment in a way that minimizes competition for metal binding sites and the Fenton reaction. This leads to the question of how the cellular metal cation bouquet can be maintained in environments that may contain a single metal in a concentration range from pM to mM. The betaproteobacterium Cupriavidus metallidurans strain CH34 is able to keep its metal homeostasis under a variety of such adverse conditions (19,28,30). The organism can be found in many mesophilic metal-contaminated environments around the globe, such as zinc deserts of Belgium (8). Key to this a...

The wastewater of livestock slaughterhouses is considered a source of antimicrobial-resistant bacteria with clinical relevance and may thus be important for their dissemination into the environment. To get an overview of their occurrence and characteristics, we investigated process water (n = 50) from delivery and unclean areas as well as wastewater (n = 32) from the in-house wastewater treatment plants (WWTPs) of two German poultry slaughterhouses (slaughterhouses S1 and S2). The samples were screened for ESKAPE bacteria (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.) and Escherichia coli. Their antimicrobial resistance phenotypes and the presence of extended-spectrum-β-lactamase (ESBL), carbapenemase, and mobilizable colistin resistance genes were determined. Selected ESKAPE bacteria were epidemiologically classified using different molecular typing techniques. At least one of the target species was detected in 87.5% (n = 28/32) of the wastewater samples and 86.0% (n = 43/50) of the process water samples. The vast majority of the recovered isolates (94.9%, n = 448/472) was represented by E. coli (39.4%), the A. calcoaceticus-A. baumannii (ACB) complex (32.4%), S. aureus (12.3%), and K. pneumoniae (10.8%), which were widely distributed in the delivery and unclean areas of the individual slaughterhouses, including their wastewater effluents. Enterobacter spp., Enterococcus spp., and P. aeruginosa were less abundant and made up 5.1% of the isolates. Phenotypic and genotypic analyses revealed that the recovered isolates exhibited diverse resistance phenotypes and β-lactamase genes. In conclusion, wastewater effluents from the investigated poultry slaughterhouses exhibited clinically relevant bacteria (E. coli, methicillin-resistant S. aureus, K. pneumoniae, and species of the ACB and Enterobacter cloacae complexes) that contribute to the dissemination of clinically relevant resistances (i.e., blaCTX-M or blaSHV and mcr-1) in the environment. IMPORTANCE Bacteria from livestock may be opportunistic pathogens and carriers of clinically relevant resistance genes, as many antimicrobials are used in both veterinary and human medicine. They may be released into the environment from wastewater treatment plants (WWTPs), which are influenced by wastewater from slaughterhouses, thereby endangering public health. Moreover, process water that accumulates during the slaughtering of poultry is an important reservoir for livestock-associated multidrug-resistant bacteria and may serve as a vector of transmission to occupationally exposed slaughterhouse employees. Mitigation solutions aimed at the reduction of the bacterial discharge into the production water circuit as well as interventions against their further transmission and dissemination need to be elaborated. Furthermore, the efficacy of in-house WWTPs needs to be questioned. Reliable data on the occurrence and diversity of clinically relevant bacteria within the slaughtering production chain and in the WWTP effluents in Germany will help to assess their impact on public and environmental health.

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PD in IMRT can be minimized by proper selection of treatment delivery method and photon beam energy. When selecting the IMRT technique in centers where compensator IMRT and MLC IMRT is available, PD burden should be taken into account. The large amount of photon components and neutron components caused by leakage radiation from the treatment head leads to the recommendation that radiation protection aspects for patients undergoing IMRT should be considered in linac design. For further clarification, additional experiments have to be carried out on other types of linacs.