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Applied and Environmental Microbiology, May 2006, p. 3175-3183, Vol. 72, No. 5
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.5.3175-3183.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Effect of Nutrient Periodicity on Microbial Community Dynamics

Militza Carrero-Colón,1 Cindy H. Nakatsu,2 and Allan Konopka1*

Department of Biological Sciences,1 Department of Agronomy, Purdue University, West Lafayette, Indiana 479072

Received 1 December 2005/ Accepted 24 February 2006

When microbes are subjected to temporal changes in nutrient availability, growth rate and substrate affinity can contribute to competitive fitness and thereby affect microbial community structure. This hypothesis was tested using planktonic bacterial communities exposed to nutrient additions at 1-, 3-, 7-, or 14-day intervals. Growth rates after nutrient addition were inversely proportional to the pulse interval and declined from 0.5 h–1 to 0.15 h–1 as the pulse interval increased from 1 to 14 days. The dynamics of community structure were monitored by 16S rRNA gene PCR-denaturing gradient gel electrophoresis. At pulse intervals of more than 1 day, the community composition continued to change over 130 days. Although replicate systems exposed to the same pulse interval were physiologically similar, their community compositions could exhibit as much dissimilarity (Dice similarity coefficients of <0.5) as did systems operated at different intervals. Bacteria were cultivated from the systems to determine if the physiological characteristics of individual members were consistent with the measured performance of the systems. The isolates fell into three bacterial divisions, Bacteroidetes, Proteobacteria, and Actinobacteria. In agreement with community results, bacteria isolated from systems pulsed every day with nutrients had higher growth rates and ectoaminopeptidase specific activities than isolates from systems pulsed every 14 days. However, the latter isolates did not survive starvation longer than those provided with nutrients every day. The present study demonstrates the dynamic nature of microbial communities exposed to even simple and regular environmental discontinuities when a substantial pool of species that can catabolize the limiting substrate is present.

* Corresponding author. Mailing address: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-2054. Phone: (765) 494-8152. Fax: (765) 494-0876. E-mail: akonopka{at}purdue.edu.

Applied and Environmental Microbiology, May 2006, p. 3175-3183, Vol. 72, No. 5
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.5.3175-3183.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.





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