Micro-spatial Distribution of Bacteria in the Rhizosphere

Abstract

Long-term experimental fields (having either no nitrogen, phosphorus, or potassium fertilizer or with complete application of N, P, and K fertilizers since 1914) were used for the investigation of bacterial habitat distribution in the rhizosphere. From the rhizosphere of Lupinus albus L., we screened rhizobacteria by their utilization ability of phytate as sole carbon (C) and phosphorus (P) source. Though almost all of the isolates were identified as Burkholderia genus, there was a wide variation in their phosphate utilization. By comparing isolates from rhizosphere soil and isolates from the rhizoplane, those isolates from the latter exhibit higher inorganic phosphate uptake ability when compared at the same extracellular phytase level. We propose that phytate-utilizing bacteria may adapt and segregate from their habitat along a spatial gradient of C and P availability in the rhizosphere. That is, rhizobacteria, which live very close to the rhizoplane, utilize phytate mainly as a P source rather than as a C source, because a large amount of C is provided from roots, whereas this may not be true for P. On the other hand, rhizosphere bacteria that live in a remote area from roots utilize phytate as a C source rather than as a P source, because the lack of available C may restrict the growth of bacteria.