The use of phospholipid fatty acids (PL-FA) in the determination of rhizosphere specific microbial communities (RSMC) of two wheat cultivars

To determine differences in microbial community structure, phospholipid fat ty acids (PL-FA) from rhizosphere bacteria of two different wheat cultivars Triticum aestivum L. (cv. Bohouth-6 and cv. Salamouni) were extracted and analyzed by gas chromatography. This approach was used to overcome the meth odological underestimation of microbial densities obtained with isolation, culture techniques and microscopic observations. Our objective was to verif y differences in PL-FA profiles from two wheat cultivars grown under contro lled environmental conditions. Principal component analysis (PCA) and clust er analysis were used to detect dissimilarities between rhizosphere microbi al communities of the two wheat cultivars and signature fatty acids (FA) we re used to determine specific differences in the community structures. PCA of the two cultivars explained 79.18% of the variance on principal componen t 1 (PC1), which accounted for Bohouth-6 rhizosphere soil. The rhizosphere soil of Salamouni accounted for 11.66% of the variance on principal compone nt 2 (PC2). The results demonstrated repeatedly the clustering of the sampl es into two distinct groups; each group belonging specifically to one of th e two wheat cultivars. Profiles of Bohouth-6 showed higher amounts of cyclo propane acid 19:0cy and Sif 7 (Sum in feature 7) than Salamouni. Those FA a re known as signature molecules for Gram-negative bacteria. This was also r eflected by the higher bacterial counts (cfu g(-1) fresh root weight) of Gr am-negative bacteria from the rhizosphere of the former than the latter. Th e results indicated that under controlled environmental conditions, wheat c ultivars of different genotypes exhibit distinct microbial colonization in their rhizosphere.