Engineered bidirectional communication mediates a consensus in a microbial biofilm consortium

Division of Chemistry and Chemical Engineering, California Institute of Technology, MC 210-41, Pasadena, CA 91125, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 11/2007; 104(44):17300-4. DOI: 10.1073/pnas.0704256104
Source: PubMed


Microbial consortia form when multiple species colocalize and communally generate a function that none is capable of alone. Consortia abound in nature, and their cooperative metabolic activities influence everything from biodiversity in the global food chain to human weight gain. Here, we present an engineered consortium in which the microbial members communicate with each other and exhibit a "consensus" gene expression response. Two colocalized populations of Escherichia coli converse bidirectionally by exchanging acyl-homoserine lactone signals. The consortium generates the gene-expression response if and only if both populations are present at sufficient cell densities. Because neither population can respond without the other's signal, this consensus function can be considered a logical AND gate in which the inputs are cell populations. The microbial consensus consortium operates in diverse growth modes, including in a biofilm, where it sustains its response for several days.

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    • "In order to achieve this, we built relay devices that send one AHL in response to receiving the other. Similar sending devices have been constructed previously (Brenner et al, 2007) using C4-and 3OC12HSL. However, since crosstalk was still present in those circuits, it was necessary for each cell to contain only one receiver protein, preventing detection in both channels. "

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    • " with constant connectivity through resources flow ( example from Kim et al . , 2008 ) . on the local partners during colony growth into available space drives assortment and automatically grants cooperators instead of cheaters more access to cooperative partners , thus disfavoring cheaters and ensuring partner fidelity ( Momeni et al . , 2013 ) . Brenner et al . ( 2007 ) similarly engineered a microbial consor - tium , but with more limited stability . The system involved positive feedbacks , in this case producing a fluorescence compound with a consensus quorum sensing ( QS ) control mechanism , and tested the cultures in liquid and solid phase ( mass - action and spatially structured ) ( Figure 3B )"
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    ABSTRACT: The metabolic capabilities of microbes are the basis for many major biotechnological advances, exploiting microbial diversity by selection or engineering of single strains. However, there are limits to the advances that can be achieved with single strains, and attention has turned toward the metabolic potential of consortia and the field of synthetic ecology. The main challenge for the synthetic ecology is that consortia are frequently unstable, largely because evolution by constituent members affects their interactions, which are the basis of collective metabolic functionality. Current practices in modeling consortia largely consider interactions as fixed circuits of chemical reactions, which greatly increases their tractability. This simplification comes at the cost of essential biological realism, stripping out the ecological context in which the metabolic actions occur and the potential for evolutionary change. In other words, evolutionary stability is not engineered into the system. This realization highlights the necessity to better identify the key components that influence the stable coexistence of microorganisms. Inclusion of ecological and evolutionary principles, in addition to biophysical variables and stoichiometric modeling of metabolism, is critical for microbial consortia design. This review aims to bring ecological and evolutionary concepts to the discussion on the stability of microbial consortia. In particular, we focus on the combined effect of spatial structure (connectivity of molecules and cells within the system) and ecological interactions (reciprocal and non-reciprocal) on the persistence of microbial consortia. We discuss exemplary cases to illustrate these ideas from published studies in evolutionary biology and biotechnology. We conclude by making clear the relevance of incorporating evolutionary and ecological principles to the design of microbial consortia, as a way of achieving evolutionarily stable and sustainable systems.
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    • "With well-defined and characterized biological properties, several QS regulators and corresponding autoinducers have also been used for synthetic gene networks. For example, LuxR/LuxI and/or LasR/LasI pairs were used to generate programmed patterns (Basu et al., 2005; Payne et al., 2013), trigger biofilm formation (Hong et al., 2012; Kobayashi et al., 2004), develop synthetic ecosystems and program population dynamics (Balagaddé et al., 2008; Brenner et al., 2007), and construct synchronized oscillators (Danino et al., 2010; Prindle et al., 2012), edge detectors (Tabor et al., 2009), and pulse generators (Basu et al., 2004). RhlR/RhlI has also been used in the study of generic mechanisms of natural selection (Chuang et al., 2009) as well as for carrying out biological computations as chemical ''wires'' (Tamsir et al., 2011). "
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