Cell culturability of Pseudomonas protegensCHA0 depends on soil pH

• Published in: FEMS microbiology ecology 2014-02, Vol.87 (2), p.441-450
• Main Authors: Mascher, Fabio, Hase, Carsten, Bouffaud, Marie-Lara, Défago, Geneviève, Moënne-Loccoz, Yvan
• Format: Article
• Language: English
• Subjects: Acidic soils; Acidity; Alkaline soils; Ecology; Microbiology; Soil pH; Soil properties
• ISSN: 0168-6496; 1574-6941
• DOI: 10.1111/1574-6941.12234

Abstract Pseudomonas inoculants may lose colony-forming ability in soil, but soil properties involved are poorly documented. Here, we tested the hypothesis that soil acidity could reduce persistence and cell culturability of Pseudomonas protegensCHA0. At 1 week in vitro, strain CHA0 was found as culturable cells at pH 7, whereas most cells at pH 4 and all cells at pH 3 were noncultured. In 21 natural soils of contrasted pH, cell culturability loss of P. protegensCHA0 took place in all six very acidic soils (pH < 5.0) and in three of five acidic soils (5.0 < pH < 6.5), whereas it was negligible in the neutral and alkaline soils at 2 weeks and 2 months. No correlation was found between total cell counts of P. protegensCHA0 and soil composition data, whereas colony counts of the strain correlated with soil pH. Maintenance of cell culturability in soils coincided with a reduction in inoculant cell size. Some of the noncultured CHA0 cells were nutrient responsive in Kogure's viability test, both in vitro and in soil. Thus, this shows for the first time that the sole intrinsic soil composition factor triggering cell culturability loss in P. protegensCHA0 is soil acidity.