Plant Growth Promoting Activity of Paenibacillus alvei WW001 and its antagonistic effects against Phytopathogenic Bacteria

Abstract

A bacterium strain with nebular growth pattern was isolated from a rice field and was identified as Paenibacillus alvei WW001. The isolate exhibited several plant-growth promoting activities including solubilization of tri-calcium phosphate at 1,152.9 µg/ml after 6 days of cultivation and production of indole acetic acid (IAA) which reached the maximum concentration of 5.1 µg/ml after 4 days of cultivation in nitrogen free medium supplemented with L-tryptophan. In addition, high production of ammonia and siderophore was detected on day 7 of cultivation (1.7 µmol/ml and 60% siderophore units respectively). Gibberellic acid production from a day-old culture in LB broth was quantified to be 79.6 µg/ml. Strain WW001 also displayed an ACC deaminase activity, albeit at a low level. Its cell-free culture supernatant (CFCS) showed antimicrobial activity against bacterial phytopathogen; Pectobacterium carotovorum DoA 263, Xanthomonas campestris DoA 1869 and X. axonopodis at 40, 1280 and 1280 Arbitrary Unit (AU)/ml respectively. Tricine SDS-PAGE analysis revealed a 3-kDa peptide associated with the observed inhibitory effect. Treating mung bean seedlings (n=30) with strain WW001 only or mixture of strain WW001 and X. campestris resulted in longer roots and higher total dry weights. Collectively, both in vitro and in vivo results attested that P. alvei WW001 is an efficient plant growth promoting rhizobacterium (PGPR) with a potent activity against bacterial phytopathogen.