Growth status of rhizobia in relation to their tolerance to low water activities and desiccation stresses |
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| Affiliation: | 1. Microbial Type Culture Collection & Gene Bank (MTCC), CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh 160 036, India;2. Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Inhoffenstrasse. 7b, D-38124 Braunschweig, Germany;3. Department of Symbiosis, Max-Planck Institute for Marine Microbiology, Bremen, Celsiusstrasse 1, D-28359, Bremen, Germany;4. NCIM-Resource Center, CSIR-National Chemical Laboratory, Pune 411008, Maharashtra, India;5. Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram 695019, Kerala, India;1. State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. BNF and Stress Biology Laboratory, Department of Botany, Jai Narain Vyas University, Jodhpur 342001, Rajasthan, India;2. The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK;3. Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK;1. Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Hwayang-dong 1, Gwangjin-gu, Seoul 143-701, Republic of Korea;2. College of Pharmacy and Medical Research Center, Chungbuk National University, Cheongju 361-763, Republic of Korea;3. Departments of Bacteriology and Genetics, The University of Wisconsin–Madison, Madison, WI 53706, USA |
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| Abstract: | Two strains of Rhizobium meliloti and one of R. japonicum were grown in broth adjusted to selected water activities (aw) using KCl, NaCl, LiCl or glycerol. The optimum doubling time for R. meliloti RCR 2011 of 2.5 h (at aw 0.999) was not affected but the yield at the stationary phase was decreased by a reduction of the aw to 0.99. Regardless of the solute used, as the aw was reduced below 0.99 growth rates and yields decreased and lag times were lengthened. The extent to which these responses changed depended on the solute used to lower the aw. Lag times were affected most when LiCl, NaCl and KCl were used to lower aw below 0.9866. No growth occurred at aw 0.969 when NaCl or KCl were used but consistent growth did occur at this aw when glycerol or LiCl were employed. In contrast with these results, LiCl was more toxic than NaCl for the slow-growing R. japonicum 5. This strain was susceptible to aw 0.9840 (glycerol).Prior growth of R. meliloti RCR 2011 and 1.5 in media of lowered aw improved the tolerance of strain RCR 2011 but not of strain 1.5 to desiccation (0% relative humidity).The growth stage of R. meliloti RCR 2011 affected the survival of this strain during storage at different r.h. values. When subjected to drought stress, stationary phase cells survived better than cells collected at three different times during the exponential growth phase.The optimum r.h. value for storage of R. meliloti strain RCR 2011 was within the range 22–43%.Extracellular polysaccharides provided protection against storage at 0% r.h. but their presence was detrimental during storage in semi-dried states. |
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