Microbial Community Interactions Are Sensitive to Small Changes in Temperature

Abstract

Microbial communities are essential for human and environmental health, often forming complex interaction networks responsible for driving ecosystem processes affecting their local environment and their hosts. Disturbances of these communities can lead to loss of interactions and thereby important ecosystem functionality. The research on what drives interactions in microbial communities is still in its infancy, and much information has been gained from the study of model communities. One purpose of using these model microbial communities is that they can be cultured under controlled conditions. Yet, it is not well known how fluctuations of abiotic factors such as temperature affect their interaction networks. In this work, we have studied the effect of temperature on interactions between the members of the model community THOR, which consists of three bacterial species: Pseudomonas koreensis, Flavobacterium johnsoniae, and Bacillus cereus. Our results show that the community-intrinsic properties resulting from their interspecies interactions are highly dependent on incubation temperature. We also found that THOR biofilms had remarkably different abundances of their members when grown at 11, 18, and 25°C. The results suggest that the sensitivity of community interactions to changes in temperature is influenced, but not completely dictated, by different growth rates of the individual members at different temperatures. Our findings likely extend to other microbial communities and environmental parameters. Thus, temperature could affect community stability and may influence diverse processes including soil productivity, bioprocessing, and disease suppression. Moreover, to establish reproducibility between laboratories working with microbial model communities, it is crucial to ensure experimental stability, including carefully managed temperature conditions.

Keywords: THOR; biofilm; community interactions; microbial communities; temperature.

FIGURE 1

Temperature-dependent biofilm production in THOR. (A) Average amount of biofilm produced by biofilm-producing co- and triple cultures of the THOR members relative to the amount of biofilm produced by the monoculture of Pseudomonas koreensis, which is represented by the dotted line. The y-axis scale is shown as ratios of the Pseudomonas koreensis monoculture biofilm production. (B) Total amount of biofilm produced by THOR members. Temperatures are given in °C. The error bars represent the standard error of the mean across four biological replicates.

FIGURE 2

Growth (OD₆₀₀) after 24 h for the THOR members grown alone at different temperatures. Temperatures are shown in °C. The error bars represent the standard error of the mean across the four biological replicates. Note that the growth has been measured when the strains have been grown alone, without the other THOR members.

FIGURE 3

Number of biofilm CFUs per well for the THOR members grown at different temperatures. Averages across six biological replicates are shown, and the error bars represent the standard error of the mean.