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.
View Article and Find Full Text PDFThe 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.
View Article and Find Full Text PDFIron is an essential nutrient in bacteria. Its ferrous form, mostly present in low oxygen and acidic pH environments, can be imported using the specific Ftr-type transport system, which encompasses the conserved FtrABCD system found in pathogenic bacteria such as Bordetella, Brucella and Burkholderia. The nonpathogenicity and versatile metabolism of Rubrivivax gelatinosus make it an ideal model to study the FtrABCD system.
View Article and Find Full Text PDFThe importance of copper resistance pathways in pathogenic bacteria is now well recognized, since macrophages use copper to fight bacterial infections. Additionally, considering the increase of antibiotic resistance, growing attention is given to the antimicrobial properties of copper. It is of primary importance to understand how bacteria deal with copper.
View Article and Find Full Text PDFCadmium, 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.
View Article and Find Full Text PDFPollution 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.
View Article and Find Full Text PDFHeavy 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.
View Article and Find Full Text PDFSilver (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.
View Article and Find Full Text PDFThe oxidase has a high affinity for oxygen and is required for growth of bacteria, including pathogens, in oxygen-limited environments. However, the assembly of this oxidase is poorly understood. Most are composed of four subunits: the catalytic CcoN subunit, the two cytochrome subunits (CcoO and CcoP) involved in electron transfer, and the small CcoQ subunit with an unclear function.
View Article and Find Full Text PDFUnlabelled: 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.
View Article and Find Full Text PDFCharacterization 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.
View Article and Find Full Text PDFPhotosynthetic 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.
View Article and Find Full Text PDFTwo genes encoding structurally similar Copper P1B -type ATPases can be identified in several genomes. Notwithstanding the high sequence and structural similarities these ATPases held, it has been suggested that they fulfil distinct physiological roles. In deed, we have shown that the Cu(+) -ATPase CtpA is required only for the activity of cuproproteins in the purple bacterium Rubrivivax gelatinosus; herein, we show that CopA is not directly required for cytochrome c oxidase but is vital for copper tolerance.
View Article and Find Full Text PDFThe relative abundance of transcripts encoding proteins involved in inorganic carbon concentrating mechanisms (CCM), detoxification of reactive oxygen species (ROS) and photosynthesis in the thermophilic cyanobacterium Synechococcus OS-B' was measured in hot spring microbial mats over two diel cycles, and was coupled with in situ determinations of incoming irradiance and microenvironmental dynamics of O(2) and pH. Fluctuations in pH and O(2) in the mats were largely driven by the diel cycle of solar irradiance, with a pH variation from ∼7.0 to ∼9.
View Article and Find Full Text PDFThe 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.
View Article and Find Full Text PDFGenes 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.
View Article and Find Full Text PDFNitrogen fixation, a prokaryotic, O2-inhibited process that reduces N2 gas to biomass, is of paramount importance in biogeochemical cycling of nitrogen. We analyzed the levels of nif transcripts of Synechococcus ecotypes, NifH subunit and nitrogenase activity over the diel cycle in the microbial mat of an alkaline hot spring in Yellowstone National Park. The results showed a rise in nif transcripts in the evening, with a subsequent decline over the course of the night.
View Article and Find Full Text PDFVascular plants contain abundant, light-harvesting complexes in the thylakoid membrane that are non-covalently associated with chlorophylls and carotenoids. These light-harvesting chlorophyll a/b binding (LHC) proteins are members of an extended CAB/ELIP/HLIP superfamily of distantly related polypeptides, which have between one and four transmembrane helices (TMH). This superfamily includes the single TMH, high-light-inducible proteins (Hlips), found in cyanobacteria that are induced by various stress conditions, including high light, and are considered ancestral to the LHC proteins.
View Article and Find Full Text PDFIn microbial mat communities of Yellowstone hot springs, ribosomal RNA (rRNA) sequence diversity patterns indicate the presence of closely related bacterial populations along environmental gradients of temperature and light. To identify the functional bases for adaptation, we sequenced the genomes of two cyanobacterial (Synechococcus OS-A and OS-B') isolates representing ecologically distinct populations that dominate at different temperatures and are major primary producers in the mat. There was a marked lack of conserved large-scale gene order between the two Synechococcus genomes, indicative of extensive genomic rearrangements.
View Article and Find Full Text PDFThermophilic cyanobacteria of the genus Synechococcus are major contributors to photosynthetic carbon fixation in the photic zone of microbial mats in Octopus Spring, Yellowstone National Park. Synechococcus OS-B' was characterized with regard to the ability to acclimate to a range of different light irradiances; it grows well at 25 to 200 micromol photons m(-2) s(-1) but dies when the irradiance is increased to 400 micromol photons m(-2) s(-1). At 200 micromol photons m(-2) s(-1) (high light [HL]), we noted several responses that had previously been associated with HL acclimation of cyanobacteria, including cell bleaching, reduced levels of phycobilisomes and chlorophyll, and elevated levels of a specific carotenoid.
View Article and Find Full Text PDFGenome sequences of two Synechococcus ecotypes inhabiting the Octopus Spring microbial mat in Yellowstone National Park revealed the presence of all genes required for nitrogenase biosynthesis. We demonstrate that nif genes of the Synechococcus ecotypes are expressed in situ in a region of the mat that varies in temperature from 53.5 degrees C to 63.
View Article and Find Full Text PDFThe facultative phototrophic nonsulfur bacterium Rubrivivax gelatinosus exhibits several differences from other species of purple bacteria in the organization of its photosynthetic genes. In particular, the puc operon contains only the pucB and pucA genes encoding the beta and alpha polypeptides of the light-harvesting 2 (LH2) complex. Downstream of the pucBA operon is the pucC gene in the opposite transcriptional orientation.
View Article and Find Full Text PDFInduction of biosynthesis of the photosystem in anoxygenic photosynthetic bacteria occurs when the oxygen concentration drops. Control of this induction takes place primarily at the transcriptional level, with photosynthesis genes expressed preferentially under anaerobic conditions. Here, we report analysis of the transcriptional control of two photosynthesis promoters, pucBA and crtI, by the PpsR factor in Rubrivivax gelatinosus.
View Article and Find Full Text PDFTwo different mechanisms for Mg-protoporphyrin monomethyl ester (MgPMe) cyclization are shown to coexist in Rubrivivax gelatinosus and are proposed to be conserved in all facultative aerobic phototrophs: an anaerobic mechanism active under photosynthesis or low oxygenation, and an aerobic mechanism active only under high oxygenation conditions. This was confirmed by analyzing the bacteriochlorophyll accumulation in the wild type and in three mutant strains grown under low or high aeration. A mutant lacking the acsF gene is photosynthetic, exhibits normal bacteriochlorophyll accumulation under low oxygenation and anaerobiosis, and accumulates MgPMe under high oxygenation.
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