Effect of maize rhizodeposits on soil microbial community structure

In order to characterise the relationships between a plant and its rhizosphere microflora, we studied the effect of rhizodeposits released by roots on the phenotypic and genetic structures of soil bacterial populations. Sterile cultures of maize (cv. F66) were cultivated for 30 days in order to obtain sterile rhizodeposits. These rhizodeposits were added daily to a test soil during the last 15 days of maize cultivation. Afterwards, the structure of bacterial communities was analysed using a phenotypic test (Biolog®) and several dominant isolates were analysed by genetic test (ARDRA). Bacteria isolated from the soil watered only with plant nutrient solution used certain carboxylic acids more intensely than bacteria isolated from the soil conditioned with F66 rhizodeposits. Among the most representative ribotypes, Bacillus mycoides dominated in soil enriched with rhizodeposits, whereas Bacillus macroides was isolated from soil without carbon amendment.