Two‐role model of an interaction network of free‐living γ‐proteobacteria from an oligotrophic environment

Abstract

Antagonistic interactions are frequently observed among bacteria in the environment and result in complex networks, which could promote co-existence, and therefore promote biodiversity. We analysed interactions of aquatic bacteria isolated by their ability to grow in Pseudomonas isolation agar from Churince, Cuatro Ciénegas, Mexico. In the resulting network, highly antagonistic and highly sensitive strains could be distinguished, forming a largely hierarchical structure. Most of the highly antagonistic strains belonged to the genus Pseudomonas. The network was sender-determined, which means that the antagonist strains had a larger influence on its structure than the sensitive ones. Very few interactions were necessary to connect all strains, implying that the network was 'small world'. The network was highly nested, having a core of highly interacting strains, with which the less antagonistic or highly sensitive interact. A probabilistic model was built, which captured most features of the network. Biological interpretation of the model implied a state in which many different antagonistic mechanisms were present, and most strains were resistant to them. Our work shows that strains of Pseudomonas from the water column at Cuatro Ciénegas have the potential to interact antagonistically with many closely related strains and that these interactions are usually not reciprocal.

Interaction networks, ecological stability, and collective antibiotic tolerance in polymicrobial infections

“…Due to the lack of comprehensive experimental data on interactions, quantitative studies of microbial ecosystems have so far relied on theoretical modeling (15,20,21) or sequencing methods (22) or have focused on incomplete subcommunities (23). Indeed, only a few studies have experimentally quantified ecological interactions in different microbial ecosystems on a larger scale (23)(24)(25)(26). Importantly, these interactions can potentially alter the efficacy of drug treatments as bacteria can protect others from the effect of antibiotics (27), in the simplest case by just degrading the drug (13,28,29).…”

Interstrain Interactions between Bacteria Isolated from Vacuum-Packaged Refrigerated Beef

“…D0b inhibited 18 of the 20 targets (Table 1). Similarly, Aguirre-von-Wobeser et al (27), using the spot-lawn method, also found Pseudomonas spp., isolated from an aquatic environment, were the most highly antagonistic strains. Published reports show plant and clinical strains of Pseudomonas (e.g., Pseudomonas putida, P. fluorescens, and other Pseudomonas spp.)…”

“…A review of the literature shows that the promotion of bacterial growth by effector isolates has been less frequently reported compared to inhibition. Possible reasons include the spot-lawn method, a test format not readily detecting growth promotion, being a primary method used in many previous studies (8,26,27) and that primary interests of applied food microbiology are in extending shelf-life and food quality.…”

“…Also, Russo et al (19) reported the growth of Brochothrix thermosphacta, a meat spoilage bacteria, decreased in the presence of LAB. We postulate testing a wide range of bacterial genera and species can provide a fuller understanding of potential complex interactions.The spot-lawn agar method (25) has been widely used to detect bacterial inhibitory activity, via reporting an inhibition zone (8,26,27). However, this method does not supply specific information about the effect of an effector on target growth, such as that achieved using broth-based assays.…”

“…The spot-lawn agar method (25) has been widely used to detect bacterial inhibitory activity, via reporting an inhibition zone (8,26,27). However, this method does not supply specific information about the effect of an effector on target growth, such as that achieved using broth-based assays.…”