Project description:Silicon (Si) has long been known to play a major physiological role in certain organisms, including some sponges and many diatoms and higher plants, leading to the recent identification of multiple proteins responsible for silicon transport in a range of algal and plant species. In mammals, despite several convincing studies suggesting that silicon is an important factor in bone development and connective tissue health, there is a critical lack of understanding in biochemical pathways that enable silicon homeostasis. Here we report the identification of a mammalian efflux silicon transporter, namely Slc34a2 (also known as NaPiIIb), which was upregulated in the kidneys of rats following chronic dietary silicon deprivation. When heterologously expressed in Xenopus laevis oocytes, the protein displayed marked silicon transport activity, specifically efflux, comparable to plant OsLsi2 transfected in the same fashion and independent of sodium and/or phosphate influx. This is the first evidence for a specific active transporter protein for silicon in mammals and suggests an important role for silicon in vertebrates.
Project description:Stress response of Methylococcus capsulatus str.Bath toward hydrogen sulfide (H2S) was investigated via physiological study and transcriptomic profiling. M. capsulatus (Bath) can grow and tolerate up to 0.75%vol H2S in headspace. Vast change in pH suggests biological relevant sulfide oxidation. Dozens of H2S-sensitive genes were identified from comparison of cell transcriptome in different H2S concentrations. Mc sulfide quinone reductase (SQR) and persulfide dioxygenase were found to be active during sulfide detoxification. Moreover, xoxF, a novel lanthanide(Ln)-dependent methanol dehydrogenase (MDH) was overexpressed in H2S while mxaF, a calcium-dependent MDH, was down-regulated, and such MDH switch phenomenon is also well known to be induced by addition of lanthanide via an as-yet-unknown mechanism. Activities in quorum sensing and RND efflux pump also suggest their role in sulfide detoxification, and might provide insight on the xoxF/mxaF switch mechanism.
Project description:In this study, the membrane biofilm reactor (MBfR) is proposed to achieve simultaneous removal of ammonium, dissolved methane, and sulfide from main-stream and side-stream anaerobic digestion liquors. To avoid dissolved methane stripping, oxygen is introduced through gas-permeable membranes, which also from the substratum for the growth of a biofilm likely comprising ammonium oxidizing bacteria (AOB), anaerobic ammonium oxidation (Anammox) bacteria, denitrifying anaerobic methane oxidation (DAMO) microorganisms, aerobic methane oxidizing bacteria (MOB), and sulfur oxidizing bacteria (SOB). A mathematical model is developed and applied to assess the feasibility of such a system and the associated microbial community structure under different operational conditions. The simulation studies demonstrate the feasibility of achieving high-level (>97.0%), simultaneous removal of ammonium, dissolved methane, and sulfide in the MBfRs from both main-stream and side-stream anaerobic digestion liquors through adjusting the influent surface loading (or hydraulic retention time (HRT)) and the oxygen surface loading. The optimal HRT was found to be inversely proportional to the corresponding oxygen surface loading. Under the optimal operational conditions, AOB, DAMO bacteria, MOB, and SOB dominate the biofilm of the main-stream MBfR, while AOB, Anammox bacteria, DAMO bacteria, and SOB coexist in the side-stream MBfR to remove ammonium, dissolved methane, and sulfide simultaneously.
Project description:The effect of sulfide stress on Desulfovibrio vulgaris Hildenborough (DvH) gene expression was determined by comparing the gene expression profiles of DvH under conditions in which sulfide was allowed to accumulate (high sulfide, average concentration 10 mM) against DvH cells grown under conditions in which sulfide was removed by continuous gassing (low sulfide, average concentration 1 mM). High sulfide significantly decreased the instantaneous growth rate constant and final cell density of the culture indicating a decreased bioenergetic fitness. Changes in gene expression caused by exposure to high sulfide were determined using full-genome DvH microarrays. The transcription of ribosomal protein-encoding genes was decreased, in agreement with the lower growth rate of DvH under high sulfide conditions. Interestingly, expression of the gene for DsrD, located downstream of the genes for dissimilatory sulfite reductase (DsrAB) was also strongly down-regulated. In contrast, the expression of many genes involved in iron accumulation, stress response and proteolysis, and chemotaxis were increased. This indicates that high sulfide represents a significant stress condition, in which the bioavailability of metals like iron may be lowered and in which proteins (e.g. metalloenzymes) may need to be refolded, or proteolytically degraded. Overall this leads to a reduced growth rate and less efficient biomass production with available resources.
Project description:The effect of sulfide stress on Desulfovibrio vulgaris Hildenborough (DvH) gene expression was determined by comparing the gene expression profiles of DvH under conditions in which sulfide was allowed to accumulate (high sulfide, average concentration 10 mM) against DvH cells grown under conditions in which sulfide was removed by continuous gassing (low sulfide, average concentration 1 mM). High sulfide significantly decreased the instantaneous growth rate constant and final cell density of the culture indicating a decreased bioenergetic fitness. Changes in gene expression caused by exposure to high sulfide were determined using full-genome DvH microarrays. The transcription of ribosomal protein-encoding genes was decreased, in agreement with the lower growth rate of DvH under high sulfide conditions. Interestingly, expression of the gene for DsrD, located downstream of the genes for dissimilatory sulfite reductase (DsrAB) was also strongly down-regulated. In contrast, the expression of many genes involved in iron accumulation, stress response and proteolysis, and chemotaxis were increased. This indicates that high sulfide represents a significant stress condition, in which the bioavailability of metals like iron may be lowered and in which proteins (e.g. metalloenzymes) may need to be refolded, or proteolytically degraded. Overall this leads to a reduced growth rate and less efficient biomass production with available resources. For each condition 2 unique biological samples were hybridized to 4 arrays that each contained duplicate spots. Genomic DNA was used as universal reference.
Project description:We investigated the effects of extracellular silicic acid on the whole Phaeodactylum triconutum transcriptome. In this work, global transcription analyses were combined with comparative studies of other elements, and detailed analyses of the silicon transporters. Our results provide insight on Si-sensing genes and further extend current models for Si uptake. Keywords: Comparative transcriptome analyses from Phaeodactylum triconutum fusiform cells acclimated in a Si-free or silicic acid medium.
Project description:Although Cochliobolus miyabeanus is an important fungal leaf pathogen on rice plants worldwide, it is largely neglected by molecular plant phytopathologists. To shed new light on the molecular and genetic basis of the rice – C. miyabeanus interaction, we compared the transcriptome of rice leaves 12h post inoculation to uninfected leaves. Even though usable sources of resistance against brown spot disease caused by C. miyabeanus are scarce, silicon application emerges as a sustainable protection strategy. Many articles report the beneficial effect of silicon on brown spot resistance. however the underlying mechanisms remain largely unclear. The influence of silicon application on the transcriptome of healthy and infected rice leaves 12hpi was compared as well in an attempt to disentangle the modulation of silicon-induced brown spot resistance.