Microbial membrane transport genes in maize rhizosphere under fertilization - a preliminary study.

Microbial DNA fragments isolated from maize rhizosphere soil under different soil fertilization treatments were sequenced, and the analysed genes contained membrane transport genes for the uptake and utilization of various substrates, nutrients ranging from sugars, vitamins, amino acids, metals, non-metals (nitrogen, oxygen, phosphorus, selenium, sulphur etc.), peptides, and osmoprotectant to quorum sensing signalling molecules. Other genes identified were involved in the export of folded and unfolded proteins and lipopolysaccharide molecules. In total, 87 gene families belonging to 32 operon groups present in soil microbes were identified. The results show that soil fertilization with 8 t/ha compost manure increased the relative abundance of these identified genes, but the most abundant of all were transport genes involved in export of unfolded proteins from within the cytoplasm of the cell to its exterior (secA), transport of peptide molecules (dppF), uptake of hydrophobic amino acids (livF, livG, livH, livK, livM) and transport of sulphur containing compounds (ssuA, ssuC, tauA, tauC). The findings of this study show that the type of nutrient-bearing material applied to the soil and the nutrient composition of the fertilizer influence the activities of soil microbes (i.e. the expression of specific functional genes) and the distribution and abundance of transport-protein producing genes necessary for sustaining the metabolic and physiological activities of soil-borne microbes.