Rapid quantification of rice root‐associated bacteria by flow cytometry

• Published in: Letters in applied microbiology Vol. 60; no. 3; pp. 237 - 241
• Main Authors: Valdameri, G, Kokot, T.B, Pedrosa, F. de O, Souza, E.M
• Format: Journal Article
• Language: English
• Published: England Published for the Society for Applied Bacteriology by Blackwell Scientific Publications [c1985-] 01-03-2015; Oxford University Press
• Subjects: A. brasilense; Azospirillum brasilense; Azospirillum brasilense - cytology; bacteria; Bacterial Load - methods; epiphytes; epiphytic bacteria; flow cytometry; Flow Cytometry - methods; H. rubrisubalbicans; Herbaspirillum - cytology; Herbaspirillum rubrisubalbicans; Oryza - microbiology; Plant Roots - microbiology; plate count; plate count method and flow cytometry; rice; rice roots; roots; A. brasilense; H. rubrisubalbicans; plate count method and flow cytometry; epiphytic bacteria; rice roots
• ISSN: 0266-8254; 1472-765X
• DOI: 10.1111/lam.12351

To understand the mechanism of plant–bacterium interaction, it is critical to enumerate epiphytic bacteria colonizing the roots of the host. We developed a new approach, based on flow cytometry, for enumerating these bacteria and used it with rice plants, 7 and 20 days after colonization with Herbaspirillum rubrisubalbicans and Azospirillum brasilense. The results were compared with those obtained with the traditional plate count method. Both methods gave similar numbers of H. rubrisubalbicans associated with rice roots (c. 10⁹ CFU g⁻¹). However, flow cytometry gave a number of viable cells of rice‐associated A. brasilense that was approx. 10‐fold greater than that obtained with the plate count method. These results suggest that the plate count method can underestimate epiphytic populations. Flow cytometry has the additional advantage that it is more precise and much faster than the plate count method. SIGNIFICANCE AND IMPACT OF THE STUDY: Determination of precise number of root‐associated bacteria is critical for plant–bacteria interaction studies. We developed a flow cytometry approach for counting bacteria and compared it with the plate count method. Our flow cytometry assay solves two major limitations of the plate count method, namely that requires long incubation times of up to 48 h and only determines culturable cells. This flow cytometry assay provides an efficient, precise and fast tool for enumerating epiphytic cells.