Investigating MerR's Selectivity: The Crosstalk Between Cadmium and Copper Under Elevated Stress Conditions.

Bacteria respond to metal pollution through sensors that control the uptake and the detoxification machineries. Specificity in metal recognition is therefore a prerequisite for triggering the appropriate response, particularly when facing a mixture of metals. In response to Cu, the purple bacterium induces the efflux Cu-ATPase CopA by the Cu regulator CopR.

Discriminating Susceptibility of Xanthine Oxidoreductase Family to Metals.

The xanthine oxidoreductase (XOR) family are metal-containing enzymes that use the molybdenum cofactor (Moco), 2Fe-2S clusters, and flavin adenine dinucleotide (FAD) for their catalytic activity. This large molybdoenzyme family includes xanthine, aldehyde, and CO dehydrogenases. XORs are widely distributed from bacteria to humans due to their key roles in the catabolism of purines, aldehydes, drugs, and xenobiotics, as well as interconversions between CO and CO.

Cadmium and Copper Cross-Tolerance. Cu Alleviates Cd Toxicity, and Both Cations Target Heme and Chlorophyll Biosynthesis Pathway in .

Cadmium, although not redox active is highly toxic. Yet, the underlying mechanisms driving toxicity are still to be characterized. In this study, we took advantage of the purple bacterium strain with defective Cd-efflux system to identify targets of this metal.

Increasing the copper sensitivity of microorganisms by restricting iron supply, a strategy for bio-management practices.

Pollution by copper (Cu ) extensively used as antimicrobial in agriculture and farming represents a threat to the environment and human health. Finding ways to make microorganisms sensitive to lower metal concentrations could help decreasing the use of Cu in agriculture. In this respect, we showed that limiting iron (Fe) uptake makes bacteria much more susceptible to Cu or Cd poisoning.

Additive effects of metal excess and superoxide, a highly toxic mixture in bacteria.

Heavy metal contamination is a serious environmental problem. Understanding the toxicity mechanisms may allow to lower concentration of metals in the metal-based antimicrobial treatments of crops, and reduce metal content in soil and groundwater. Here, we investigate the interplay between metal efflux systems and the superoxide dismutase (SOD) in the purple bacterium Rubrivivax gelatinosus and other bacteria through analysis of the impact of metal accumulation.

Silver and Copper Acute Effects on Membrane Proteins and Impact on Photosynthetic and Respiratory Complexes in Bacteria.

Silver (Ag) and copper (Cu) ions have been used for centuries in industry, as well as antimicrobial agents in agriculture and health care. Nowadays, Ag is also widely used in the field of nanotechnology. Yet, the underlying mechanisms driving toxicity of Ag ions are poorly characterized.

c-Type Cytochrome Assembly Is a Key Target of Copper Toxicity within the Bacterial Periplasm.

Unlabelled: In the absence of a tight control of copper entrance into cells, bacteria have evolved different systems to control copper concentration within the cytoplasm and the periplasm. Central to these systems, the Cu(+) ATPase CopA plays a major role in copper tolerance and translocates copper from the cytoplasm to the periplasm. The fate of copper in the periplasm varies among species.

Oxygen-dependent copper toxicity: targets in the chlorophyll biosynthesis pathway identified in the copper efflux ATPase CopA deficient mutant.

Characterization of a copA(-) mutant in the purple photosynthetic bacterium Rubrivivax gelatinosus under low oxygen or anaerobic conditions, as well as in the human pathogen Neisseria gonorrhoeae identified HemN as a copper toxicity target enzyme in the porphyrin synthesis pathway. Heme synthesis is, however, unaffected by copper under high oxygen tension because of the aerobic coproporphyrinogen III oxidase HemF. Nevertheless, in the copA(-) mutant under aerobiosis, we show that the chlorophyll biosynthesis pathway is affected by excess copper resulting in a substantial decrease of the photosystem.

EmbRS a new two-component system that inhibits biofilm formation and saves Rubrivivax gelatinosus from sinking.

Photosynthetic bacteria can switch from planktonic lifestyle to phototrophic biofilm in mats in response to environmental changes. The mechanisms of phototrophic biofilm formation are, however, not characterized. Herein, we report a two-component system EmbRS that controls the biofilm formation in a photosynthetic member of the Burkholderiales order, the purple bacterium Rubrivivax gelatinosus.

Adaptation to oxygen: role of terminal oxidases in photosynthesis initiation in the purple photosynthetic bacterium, Rubrivivax gelatinosus.

The appearance of oxygen in the Earth's atmosphere via oxygenic photosynthesis required strict anaerobes and obligate phototrophs to cope with the presence of this toxic molecule. Here we show that in the anoxygenic phototroph Rubrivivax gelatinosus, the terminal oxidases (cbb(3), bd, and caa(3)) expand the range of ambient oxygen tensions under which the organism can initiate photosynthesis. Unlike the wild type, the cbb(3)(-)/bd(-) double mutant can start photosynthesis only in deoxygenated medium or when oxygen is removed, either by sparging cultures with nitrogen or by co-inoculation with strict aerobes bacteria.

Organization and expression of photosynthesis genes and operons in anoxygenic photosynthetic proteobacteria.

Genes belonging to the same metabolic route are usually organized in operons in microbial genomes. For instance, most genes involved in photosynthesis were found clustered and organized in operons in photosynthetic Alpha- and Betaproteobacteria. The discovery of Gammaproteobacteria with a conserved photosynthetic gene cluster revives the questions on the role and the maintenance of such organization in proteobacteria.

Effect of the nitrogen source on phycobiliprotein synthesis and cell reserves in a chromatically adapting filamentous cyanobacterium.

Cyanobacteria can utilize nitrate or ammonium as a source of fixed nitrogen for cell growth. In the filamentous Calothrix sp. strain PCC 7601, these two sources of nitrogen differently influenced the phycobiliprotein composition of the phycobilisomes, the major light-harvesting antennae.