P-361 - Molecular characterization of siderophore production in taxonomically diverse plant beneficial bacterial candidates from rhizospheric niches of Dicranopteris and Rice

The dynamics of plant-microbe interactions are multifaceted, impacting the distribution of microbes in host plants where the role of microbial siderophores is essential yet insufficiently explored. Siderophores are small organic chelators of iron and sometimes heavy metals.  This study delves into the molecular mechanism of siderophore production by plant growth promoting Enterobacter sp. DRP3 and Brucella sp. RRSP16, isolated from the rhizospheres of Dicranopteris and Rice plants respectively. Siderotyping, showed that DRP3 produces both catecholate and hydroxamate siderophores, in contrast to only single type by RRSP16. Whole genome sequencing and further in-silico analysis provided insights into the complete metabolic pathways for enterobactin and aerobactin in DRP3, while partial pathways for siderophore biosynthesis was  observed in RRSP16. Gene expression study by qRT-PCR, highlighted a significant upregulation of entC and entF by 5.02 and 1.90 fold respectively (enterobactin biosynthesis), alongside a 3.12-fold increase in iucC expression (aerobactin biosynthesis) in absence of Fe³⁺ in DRP3. In-vivo tracking results validated that both isolates colonized the rice roots, even under Pb(II) stress. Despite the variations in their siderophore and quorum sensing mechanisms, both isolates significantly enhance the growth of rice. This study will undoubtedly improve our understanding of the involvement of siderophore production during beneficial plant-microbe interaction.