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Applied and Environmental Microbiology, July 2002, p. 3597-3605, Vol. 68, No. 7
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.7.3597-3605.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Noninvasive Quantitative Measurement of Bacterial Growth in Porous Media under Unsaturated-Flow Conditions {dagger}

R. R. Yarwood,1,2 M. L. Rockhold,2,3 M. R. Niemet,4 J. S. Selker,2 and P. J. Bottomley1,5*

Department of Microbiology,1 Department of Bioengineering,2 Department of Crop and Soil Science, Oregon State University, Corvallis, Oregon 97331-3804,5 Pacific Northwest National Laboratory, Richland, Washington 99352,3 CH2M Hill, Corvallis, Oregon 97330-35384

Received 26 November 2001/ Accepted 16 April 2002

Glucose-dependent growth of the luxCDABE reporter bacterium Pseudomonas fluorescens HK44 was monitored noninvasively in quartz sand under unsaturated-flow conditions within a 45- by 56- by 1-cm two-dimensional light transmission chamber. The spatial and temporal development of growth were mapped daily over 7 days by quantifying salicylate-induced bioluminescence. A nonlinear model relating the rate of increase in light emission after salicylate exposure to microbial density successfully predicted growth over 4 orders of magnitude (r2 = 0.95). Total model-predicted growth agreed with growth calculated from the mass balance of the system by using previously established growth parameters of HK44 (predicted, 1.2 x 1012 cells; calculated, 1.7 x 1012 cells). Colonization expanded in all directions from the inoculation region, including upward migration against the liquid flow. Both the daily rate of expansion of the colonized zone and the population density of the first day's growth in each newly colonized region remained relatively constant throughout the experiment. Nonetheless, substantial growth continued to occur on subsequent days in the older regions of the colonized zone. The proportion of daily potential growth that remained within the chamber declined progressively between days 2 and 7 (from 97 to 13%). A densely populated, anoxic region developed in the interior of the colonized zone even though the sand was unsaturated and fresh growth medium continued to flow through the colonized zone. These data illustrate the potential of a light transmission chamber, bioluminescent bacteria, and sensitive digital camera technology to noninvasively study real-time hydrology-microbiology interactions associated with unsaturated flow in porous media.

* Corresponding author. Mailing address: Department of Microbiology, Rm. 220 Nash Hall, Oregon State University, Corvallis, OR 97331-3804. Phone: (541) 737-1844. Fax: (541) 737-0496. E-mail: Peter.Bottomley{at}orst.edu.

{dagger} Technical Paper no. 11,840 of the Oregon Agricultural Experiment Station.

Applied and Environmental Microbiology, July 2002, p. 3597-3605, Vol. 68, No. 7
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.7.3597-3605.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Rockhold, M. L., Yarwood, R. R., Niemet, M. R., Bottomley, P. J., Selker, J. S. (2005). Experimental Observations and Numerical Modeling of Coupled Microbial and Transport Processes in Variably Saturated Sand. Vadose Zone J 4: 407-417 [Abstract] [Full Text]  
  • Rockhold, M. L., Yarwood, R. R., Selker, J. S. (2004). Coupled Microbial and Transport Processes in Soils. Vadose Zone J 3: 368-383 [Abstract] [Full Text]  


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