Alterations in the rhizobacterial community associated with European alder growth when inoculated with PGPR strain Bacillus licheniformis
Ramos, B.L.cas-Garcia, J.; Probanza, A.B.rrientos, M.; Gutierrez-Manero, F.
Environmental and experimental botany 49(1): 61-68
Alder seedlings were either inoculated with a suspension of Bacillus licheniformis, or left non-inoculated (controls) and grown in two different soils under controlled conditions. For 8 weeks after inoculation, plant shoot and root systems were measured, nodules counted, and shoot and root length and surface area determined. In addition to plant growth, changes in the bacterial rhizosphere composition and inoculum levels were determined using the phospholipid fatty acid (PLFA) profile from the rhizosphere soil and from culturable bacteria from the rhizosphere (culturable PLFAs), respectively. These studies show the differential effect of B. licheniformis on alder growth depending on the soil used. Increases in leaf surface area were significant only when grown in Soil A, while root growth increased in both soils. Effects were more pronounced in Soil A. Changes in the rhizosphere community after inoculation with B. licheniformis disappeared within a short period in both soils, 6 weeks in Soil A and only 2 in Soil B. B. licheniformis apparently survived at least 8 weeks in the rhizosphere, as revealed by culturable PLFA profiles. Thus, increases in plant growth can be attributed to changes in the rhizosphere microbial communities, especially in the culturable fraction, due to the presence of the inoculated bacteria in soil. Given the different composition of soils, availability of nutrients must also be considered.