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Aquatic Microbial Ecology

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AME 35:131-139 (2004)  -  doi:10.3354/ame035131

Impact of initial phage/host ratio and nutrient addition on coexistence in a phage-host system

Arite Wolf1,2,5, TianLing Zheng3,6, Karl-Paul Witzel4, Günter Jost1,*

1Institut für Ostseeforschung Warnemünde, Seestraße 15, 18119 Rostock, Germany
2Fachbereich Biologie, Universität Rostock, Ökologie, Freiligrathstraße 7-8, 18051 Rostock, Germany
3Environmental Sciences Research Center, Xiamen University, Xiamen, 361005, PR China
4Max-Planck-Institut für Limnologie, PO Box 165, 24302 Plön, Germany
5Present address: Fachbereich Biologie, Mikrobiologie, Universität Rostock, Albert-Einstein-Straße 3, 18059 Rostock, Germany
6Present address: School of Life Sciences, Xiamen University, Xiamen, 361005, PR China
*Corresponding author. Email:

ABSTRACT: The influence of specific phages on the population size of their host bacteria was studied using a model system of a selected phage and its host bacterium, identified as Aeromonas sp. isolated from a lagoon in the southern Baltic Sea. For all initial phage/host ratios (PBR [phage/bacterium ratio] of 0.1 to 100), phage and host abundances reached a ratio of about 5 to 50 within the first 8 h. Interestingly, this range of phage/bacterium ratios of a single phage-host system corresponds to the ratio of virus to bacterial abundance found in natural habitats. The proportion of sensitive cells containing mature phage particles increased in the first 4 h to 40%, and then decreased (at rates dependent on the initial ratio) within 12 h (initial PBR of 100), 48 h (initial PBR of 10 and 1) and 72 h (initial PBR of 0.1) to less than 1%. There was evidence for rapid development of immunity (probably pseudolysogeny), especially at high initial phage concentrations. After 96 h incubation, carbon, nitrogen and phosphorus were added to improve the nutritional state of the bacteria. Although nutrients were added to all treatments when phage/host ratios were nearly equal, quite different reactions were observed for the bacteria populations with different initial PBRs. Those with low initial PBRs showed the most pronounced increase.

KEY WORDS: Phage-host system · Immunity · Lysogeny · Pseudolysogeny · Phage/bacterium ratio · Coexistence

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