Differences between bacterial associations with two root types of Vicia faba L

Abstract

Differences between various inherent physiological characteristics of lateral roots and of taproots of faba bean plants (Vicia faba L.) have been described in the literature. The question as to whether distinct bacterial communities inhabit each of those root types calls for further investigation. This question was tackled using aeroponically grown plants, i.e., plants that were grown under conditions as homogeneous as possible. Samples of the apical 5 cm of taproots and of lateral roots were compared. Metabolic fingerprints of root bacterial communities were analyzed using the Biolog® assay. Specificity of colonization of the different root types by specific bacterial taxa was examined by the Real-Time Polymerase Chain Reaction (PCR) method. Root bacterial communities produced distinct metabolic fingerprints for each of the two root types. Herbaspirillum spp. were found to be associated with lateral roots but not with taproots both under non-saline and saline (50 mM NaCl) conditions. No significant differences were found in the abundance of bacteria with respect to either root type or salinity. It is concluded that different root types, even within single root systems, differ not only in their physiological traits but also in their bacterial associations. Such associations might have adaptive advantages.

Abbreviations:

• AWCD: Average well colour development
• CFU: Colony forming units
• LB: Lauria-Bertani
• MDSA: Multidimensional scaling analysis
• PCR: Polymerase Chain Reaction
• RBC: Root bacterial community
• RFW: Root fresh weight

Key words:

• Bacterial community
• Biolog®
• Real-Time PCR
• root types
• Vicia Faba L.

Acknowledgements

The authors heartily thank Professor Eugene Rosenberg, Department of Biotechnology and Molecular Microbiology, Faculty of Life Science, Tel Aviv University for his help and his advice. We thank the Minerva Foundation for enabling the visit of MO to Grossbeeren, Germany.