Bacterial denitrification gene expression in the rhizosphere

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The overall research program will quantify denitrification gene expression via reverse transcription- Real time PCR in Pseudomonas mandelli and indigenous soil microorganisms under diverse soil conditions including the rhizosphere. Global warming has been identified as a priority international threat to our common, shared, biosphere, resulting in immense social, environmental, agricultural, public health and economic consequences that cannot be easily estimated and forecasted. Nitrous oxide (N2O) is one of several greenhouse gases that contribute to global warming. Atmospheric concentrations of N2O have been increasing at an alarming rate of 0.2-0.3% per year since the preindustrial period. A series of experiments have been designed by myself and my collaborators, for a 5-year period of research to understand denitrification gene expression in pure culture, bulk soil and the rhizosphere. P.mandelii is a predominant denitrifying bacterium isolated from the soils I have been researching. It is therefore prudent and logical to continue researching this species to complete the data sets required for a more complete understanding. The complex functional relationships between plants, bacteria and the soil environment are being researched to determine the effect of the environment including the rhizosphere effect on the suite of denitrifying gene expressions (via Real-time PCR reverse transcription, digital gene expression analysis and proteomics) in pure cultures, bulk and rhizosphere soils. Nitrous oxide emissions and depletion of the N-substrates will also be measured. The rhizosphere under the influence of plant roots may exhibit significantly different rates of gene expression compared to the same bulk soil. Increasing amounts of nitrate and a higher density of denitrifiers in the rhizosphere could result in longer induction times of denitrification genes and subsequently, more N2O product released into the atmosphere, but only if N-substrate is available by addition of fertilizer and/or soil nitrification is occurring under aerobic conditions before denitrification commences under anaerobic conditions.