ISOLATION, SCREENING, OPTIMISATION, CHARACTERISATION OF SIDEROPHORE PRODUCING BACTERIA FROM PLANT RHIZOSPHERE

A total of 97 bacterial isolates were obtained from plant rhizosphere collected from Vellamadam village, Tuticorin district, Tamil Nadu, India. Eight of the isolates showed positive for the production of siderophore by Blue CAS plate assay. Isolate SA6 showed maximum siderophore production of 66.45% SU in Iron Deficient Succinate Medium (IDSM). The isolate SA6 produced carboxylate type of siderophore. There was significantly increased siderophore production on day 2 of incubation (62.87% SU) and decline on day 3. Maximum siderophore production was observed at pH 6.8 (50.31% SU) and temperature 34°C (85.1% SU). IDSM showed the maximum siderophore production (75.90% SU) followed by Barbhaiya & Rao media (67.12% SU). Glucose as a carbon source stimulated siderophore production of 55.7% SU. Maximum siderophore (82.33% SU) was obtained with urea as an independent nitrogen source the followed by citric acid (81.46% SU). Tryptophan showed a maximum siderophore production with 84.41 SU %, followed by Tyrosine (82.6% SU). Iron concentration of 100 mM was optimum for the production of siderophore. Maximum Siderophore production (91.74% SU) was observed with Fe-EDTA as iron chelator followed by Tris -EDTA (91.62% SU). Plant growth promoting activities such as HCN production, Indole Acetic Acid (IAA) production and nitrate reduction was exhibited by isolate SA 6 which indicates it to be a good PGPR. The gene sequencing of the isolate SA6 has 97 % similarity with Escherichia fergusonii