Physiological stress in batch cultures of Pseudomonas putida 54G during toluene degradation |
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Authors: | R G Mirpuri W L Jones G A McFeters H F Ridgway |
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Institution: | (1) Basys Technologies, 1345 Northland Dr, Mendota Heights, MN 55120-1141, USA, US;(2) Center for Biofilm Engineering, 366 EPS, PO Box 173980, Montana State University – Bozeman, Bozeman, MT 59717-3980, USA, US;(3) Biotechnology Department, Orange County Water District, PO Box 8300, Fountain Valley, CA 92728-8300, USA, US |
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Abstract: | Physiological stress associated with toluene exposure in batch cultures of Pseudomonas putida 54G was investigated. P. putida 54G cells were grown using a continuous vapor phase feed stream containing 150 ppmv or 750 ppmv toluene as the sole carbon
and energy source. Cells were enumerated on non-selective (R2A agar plates) and a selective minimal medium incubated in the
presence of vapor phase toluene (HCMM2). Differential recovery on the two media was used to evaluate bacterial stress, culturability
and loss of toluene-degrading capability. A majority of the bacteria were reversibly stressed and could resume active colony
formation on selective medium after passage on non-selective medium. A small fraction of the bacterial cells suffered an
irreversible loss of toluene degradation capability and were designated as Tol− variants. Numbers of stressed organisms increased with duration of toluene exposure and toluene concentration and coincided
with accumulation of metabolic intermediates from incomplete toluene degradation. Respiring cell numbers in the batch cultures
decreased as injury increased, indicating a possible relationship between respiring and injured cells. Rate expressions for
injury, for formation of Tol− variants and for growth of Tol− variants were determined by calibrating a theoretical model to the results obtained. These rate expressions can be used
to calibrate bioreactor models, and provide a basis for better design and control of bioremediation systems.
Received 01 July 1996/ Accepted in revised form 25 March 1997 |
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Keywords: | : biodegradation toluene P putida 54G physiological stress injury |
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