Microbial protease encoding genes in soil: diversity, abundance and enzymatic activity

The objective of this research was to identify potential factors that govern the abundance, diversity and expression of genes encoding proteases in soil. I studied the response of protease encoding genes and proteolytic community structure of soil under different conditions. Three different approaches have been used for this thesis : 1. Using a rhizobox approach effect of root exudates from plants differing in Nitrogen utilizing efficiencies (NUE), on protease enzyme activity, molecular diversity and abundance of proteolytic genes was investigated. We observed a higher molecular diversity, abundance and higher enzyme activity associated with higher NUE cultivar. Furthermore, effect of root exudates can’t be ignored and rhizosphere soil exhibited significantly higher results. 2. Effect of elevated atmospheric CO2 was studied on rhizosphere and bulk soil from a Free Air Carbon dioxide Enrichment (FACE) field that was exposed to 550 ppm of CO2. We observed a reduction in abundance of apr protease genes. This decrease has been observed in both rhizosphere and bulk soil. We concluded that in eCO2 conditions, the action on soil microbes is not limited via root exudates but also mediated through fixation of CO2 directly by mircobes under high partial pressure. 3. Changes in expression of proteases during day and night has been studied in a green-house experiment where Barley rhizosphere soil was subjected to metatranscriptome analysis. Samples were collected during dark and light exposed period and mRNA was isolated which was later sequenced on an Illumina sequencer.