The impact of copper, nitrate and carbon status on the emission of nitrous oxide by two species of bacteria with biochemically distinct denitrification pathways

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From Functional Potential of Soil Bacterial Communities Towards Petroleum Hydrocarbons Bioremediation

Molecular ecology researches are rapidly advancing the knowledge of microorganisms associated with petroleum hydrocarbon degradation, one of the major large-scale pollutants in terrestrial ecosystems. The design and monitoring of bioremediation techniques for hydrocarbons rely on a thorough understanding of the diversity of enzymes involved in the processes of hydrocarbon degradation and the microbes that harbor their allocated genes. This review describes the impact of hydrocarbon pollution on soil microbial communities, the state of the art of detecting functional genes, and functional groups. We will focus on i) the structure, function and succession behavior of microbial communities exposed to hydrocarbons, ii) key genes and pathways, iii) future prospect into bioremediation of petroleum hydrocarbons in aerobic environments. The aim is to get a fundamental insight in these issues to ultimately improve petroleum hydrocarbons bioremediation. Keywords: Petroleum hydrocarbons, microbial communities, functional genes, oil degradation, bioremediation. DOI: 10.7176/JBAH/9-10-01 Publication date:May 31st 201

Circular spectropolarimetric sensing of chiral photosystems in decaying leaves

Circular polarization spectroscopy has proven to be an indispensable tool in photosynthesis research and (bio)-molecular research in general. Oxygenic photosystems typically display an asymmetric Cotton effect around the chlorophyll absorbance maximum with a signal $\leq 1 \%$. In vegetation, these signals are the direct result of the chirality of the supramolecular aggregates. The circular polarization is thus directly influenced by the composition and architecture of the photosynthetic macrodomains, and is thereby linked to photosynthetic functioning. Although ordinarily measured only on a molecular level, we have developed a new spectropolarimetric instrument, TreePol, that allows for both laboratory and in-the-field measurements. Through spectral multiplexing, TreePol is capable of fast measurements with a sensitivity of $\sim 1*10^{-4}$ and is therefore suitable of non-destructively probing the molecular architecture of whole plant leaves. We have measured the chiroptical evolution of \textit{Hedera helix} leaves for a period of 22 days. Spectrally resolved circular polarization measurements (450-900 nm) on whole leaves in transmission exhibit a strong decrease in the polarization signal over time after plucking, which we accredit to the deterioration of chiral macro-aggregates. Chlorophyll \textit{a} levels measured over the same period by means of UV-Vis absorption and fluorescence spectroscopy showed a much smaller decrease. With these results we are able to distinguish healthy from deteriorating leaves. Hereby we indicate the potency of circular polarization spectroscopy on whole and intact leaves as a nondestructive tool for structural and plant stress assessment. Additionally, we underline the establishment of circular polarization signals as remotely accessible means of detecting the presence of extraterrestrial life.Comment: 29 pages, 6 figure

Circular spectropolarimetric sensing of higher plant and algal chloroplast structural variations

Photosynthetic eukaryotes show a remarkable variability in photosynthesis, including large differences in light harvesting proteins and pigment composition. In vivo circular spectropolarimetry enables us to probe the molecular architecture of photosynthesis in a non-invasive and non-destructive way and, as such, can offer a wealth of physiological and structural information. In the present study we have measured the circular polarizance of several multicellular green, red and brown algae and higher plants, which show large variations in circular spectropolarimetric signals with differences in both spectral shape and magnitude. Many of the algae display spectral characteristics not previously reported, indicating a larger variation in molecular organization than previously assumed. As the strengths of these signals vary by three orders of magnitude, these results also have important implications in terms of detectability for the use of circular polarization as a signature of life.Comment: 25 pages, 9 figure