COMPARISON OF AEROBIC HETEROTROPHIC TAXA ISOLATED FROM 4 ROOT DOMAINSOF MATURE SUGAR-BEET (BETA-VULGARIS)

The distribution of bacteria in the rhizosphere, rhizoplane, interior root tissues (core) and lower root (all tissues) of mature sugar beet roots (Beta vulgaris) was compared. Of 556 isolates, 102 species from 40 genera were identified by fatty acid methyl ester gas-chromatograph ic (FAME-GC) analysis. The ten most common genera(Bacillus, 14%; Arthr obacter, 12%; Pseudomonas, 11%; Aureobacterium, 9%; Micrococcus, 6%; X anthomonas, 5%; Alcaligenes, 4%; Flavobacterium, 3%; Agrobacterium, 3% ; Microbacterium, 3%) accounted for 70% of isolates, and were found in each of three root domains (rhizosphere, rhizoplane and interior root tissues) on the two principal sampling occasions. Gram-positive strai ns were more abundant in the rhizosphere than the rhizoplane. Compared to the rhizoplane, rhizosphere bacterial communities were represented by a less diverse, more hierarchical distribution of species where tw ice as many isolates formed late developing colonies on isolation plat es. Between October and January, the bacteria isolated from root inter ior tissues acquired a distinct change in taxonomic pattern, with decr eased diversity and increased hierarchy. A bacterial continuum of simi lar taxa was observed which extended from the rhizosphere to interior root tissues.