ENTEROBACTER-AGGLOMERANS, PHOSPHATE SOLUBILIZING BACTERIA, AND MICROBIAL ACTIVITY IN SOIL - EFFECT OF CARBON-SOURCES

Soil contains large amount of phosphorus that exists in insoluble form s. Some soil bacteria like Enterobacter agglomerans may have the capab ility to solubilize insoluble P and hydrolyze organic P for plant grow th. These phosphate-solubilizing bacteria (PSB) may be stimulated by o rganic energy sources added to or found in soils. To examine the effec t of organic energy sources on the survival of E. agglomerans and soil microbial activities; E. agglomerans were introduced into unsterilize d soil containing 1% hydroxyapatite (HA) and either 1% glucose (GL), p hytic acid dodecasodium salt (PA), glycerol-2-phosphate disodium salt (GP), soluble starch (SS) or no addition. Two controls were used: cont rol 1: without E. agglomerans (C1) and control 2: with E. agglomerans (C2). E. agglomerans introduced in C2 treatment increased soil microbi al biomass, phosphatase activity, and P solubilization compared to C1 at 2 d; however, with time there was no significant difference in trea tments; Acid and alkaline phosphatase activities in GL and SS treatmen ts were greater when compared to PA and GP; however, P concentration w as greater in PA and GP treatments. Phytic acid and glycerol-2-phospha te may provide the necessary energy to solubilize HA as well as organi c phosphate which is hydrolyzed by phosphatase. Soil microbial biomass C in GL and SS treatments were higher compared to PA and GP treatment s. When only LB culture was added, E. agglomerans was not detectable a fter 22 d. Any additional mineralizable C contributes to the survival of E. agglomerans with time. (C) 1998 Elsevier Science Ltd. All rights reserved.