AUTHOR=Liu Xiaolin , Zhang Kaiye , Liu Yanan , Xie Zhihong , Zhang Chengsheng 

TITLE=Oxalic Acid From Sesbania rostrata Seed Exudates Mediates the Chemotactic Response of Azorhizobium caulinodans ORS571 Using Multiple Strategies

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 10 - 2019

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02727

DOI=10.3389/fmicb.2019.02727

ISSN=1664-302X

ABSTRACT=Chemotaxis towards seed exudates is important in the establishment of microbe-plant associations. The objective of this work was to explore if organic acids from seed exudates of Sesbania rostrata play a role in recruiting Azorhizobium caulinodans ORS571 in the plant rhizosphere. High performance liquid chromatography (HPLC) was used to analyze the organic acids content in seed exudates of S. rostrata and to further determine their roles in A. caulinodans growth and chemotactic response. Succinic, acetic, citric, oxalic, and lactic acids were the most abundant, and except for oxalic acid, they could support A. caulinodans growth as a sole carbon source. TlpA1, a transmembrane chemoreceptor was found to be involved in the chemotactic response to these organic acids. Oxalic acid had a direct role in the chemotactic response, but it also had an indirect role by promoting or inhibiting the chemotaxis response towards other chemoeffectors. Furthermore, the indirect role of oxalic acid on other chemoeffectors was concentration dependent. The effect of oxalic acid at different concentrations on the host root colonization was also determined. By using different strategies, oxalic acid appears to play a major role in early steps of the association of A. caulinodans and its host plant.