Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/21/2006
Publication Date: 6/1/2006
Citation: Mudgal, P., Breidt, F., Lubkin, S., Sandeep, K.P. 2006. Quantifying the significance of phage attack on starter cultures: A mechanistic model for population dynamics of phage and their hosts isolated from fermenting sauerkraut. Applied and Environmental Microbiology. 72:3908-3195. Interpretive Summary: We have recently found that bacterial viruses are present in vegetable fermentations, possibly in large numbers. While harmless to humans, these viruses can alter the microbial ecology of vegetable fermentations, particularly low salt fermentations controlled with starter cultures. Low salt fermentations are currently being investigated as a means to reduce chloride waste from commercial fermentations. To aid in the understanding of the impact of bacterial viruses on fermentation ecology, we have developed a mathematical model of bacterial–virus interactions. The model was validated by laboratory experiments with two different virus-host pairs, and novel features of the kinetics of virus-host interactions were discovered. In addition to aiding in the development of controlled vegetable fermentations, the results of this study may have broader application in understanding bacterial-virus interactions for other types of commercial bacterial fermentations.
Technical Abstract: We investigated the possibility of using starter cultures in sauerkraut fermentation and, thereby, reducing the quantity of salt used in the process. This, in turn, would reduce the amount of waste salt that would end up in our water resources. Phage, naturally present in sauerkraut fermentation, could potentially affect the starter cultures introduced. Thus, a mechanistic mathematical model was developed to quantify the growth kinetics of the phage and starter cultures. The model was validated by independent experiments with two Leuconostoc mesenteroides strains isolated from sauerkraut and their corresponding phage. Model simulations and experimental evidence showed the presence of phage-resistant cell populations in starter cultures which replaced phage-sensitive cells, even when the initial phage density and multiplicity of infection (MOI) were low in the MRS media. Based on the results of model simulation and parameter optimization, it was suggested that the kinetic parameters of phage-host interaction, especially adsorption rate, vary with the initial phage and host densities, and with time. The model was validated in MRS broth. Therefore, the effect of heterogeneity and other environmental factors such as temperature and pH should be considered to make the model applicable to commercial fermentations.