Emergence in communities – from quorum sensing in bacteria to human cohorts

I got into an interesting conversation recently at a conference about what “emergence” looks like in practice. It’s one of those words that’s being increasingly used to describe the power of communities to self-organise (e.g. “emergence over authority” is one of the chapters of Whiplash by Joi Ito of Media Lab). And yet I hadn’t fully appreciated how emergence plays out in groups. At least, until I realised that emergence is what I was working on as a graduate student – without ever describing it in those terms.

My biochemistry research focused on quorum sensing in bacteria – a mechanism by which a group of bacteria of the same species coordinate to produce a compound at high population density that’s not seen when the same bugs exist at a lower density. The specific compound produced varies with the type of bacteria – sometimes it’s a pigment, others an antibiotic, or a specific set of enzymes. But essentially, quorum sensing is about how bacteria communicate as a group to decide when to make this population-dependent chemical. So I often joke that my interests in collaborative behaviour took the long route from studying uni-cellular organisms to multi-cellular ones! 

Emergence in bacteria – a lightbulb moment!
Image credit: https://www.flickr.com/photos/ajc1/252308050/

Making sense of messages as a group

So how does quorum sensing work? Typically, each of the bacteria in a population will produce a pheromone, which diffuses into the surrounding environment. If you trap the bacteria in a closed space, such as the light organ of the deep sea squid (the bulb that sits on the top of the squid’s head) then as the bacteria multiply, their overall cell density will increase. At the same time, this means that the pheromone that they’re each producing starts building up too.

Because its freely diffusible between the bacteria, the pheromone can enter the cells of surrounding bacteria. At a high enough concentration it will consistently engage with DNA-binding proteins within those cells. Once engaged by the pheromone, the binding proteins change shape and attach to the bacterium’s DNA, switching on certain genes. In the case of Vibrio fischeri bacteria that colonise the light organ of the squid, this results in the production of enzymes that cause bioluminescence. There’s a “Eureka!” lightbulb moment when the light organ of the squid is lit up by the bacterial biochemical reactions taking place.   

As well as being a pretty cool phenomenon in its own right, what’s particularly interesting now that I’m focused on human communities is how this is an example of an emergent behaviour. There’s no authoritative “boss” bacterium measuring the overall cell density and deciding when the others should turn on their bioluminescence genes. The “message” to do that is deciphered separately by each bacterium, based on the concentration of pheromone present. 

From bugs to humans – emergence in cohorts

Most human communities don’t start off in this emergent, spontaneously self-organising configuration and so they benefit from someone to create a space for their interactions, ensure participation and maybe also oversee various governance functions – the community manager or group facilitator. But sometimes groups do get to an emergent state, for example when a mature cohort forms. Typically, then the group becomes self-facilitating with individual group members each having a role in influencing the group’s overall activities. 

This became particularly apparent at the mid-year meeting of the AAAS Community Engagement Fellows where the Fellows are increasingly becoming self-organising as a group. Reflecting on the quorum sensing example, I think there are a few similarities that are required for emergence within a cohort:

  • Equality between group members. All the bacteria in a quorum produce the pheromone signalling molecule in roughly the same amount. Within a human community, I suggest that this translates as members having equal opportunities to contribute to the group’s activities which looks like equal contribution by each member to the group over time.
  • An enclosed space for the community. The bacteria in the light organ of the squid are present within an enclosed space – which enables the emergent behaviour (the switching on of bioluminescence) to occur. So too with a cohort – it’s a bounded group which often meets in retreat-like circumstances to focus intensely on information sharing and learning together. Is it that intense, connected interaction within dedicated spaces that helps emergence to arise?
  • There’s a “messenger molecule” that signals for emergence to occur. In quorum sensing bacteria this is the diffusible pheromone. Within a human cohort, is this currency trust? Once the cohort has spent a certain amount of time together in their protected space, the level of trust is such that group members are willing to consistently self-disclose, listen deeply to one another, set aside reactive behaviours and ultimately to act as a group capable of emergent behaviour, rather than a collection of individuals.

What do you think? Have you ever participated in a cohort experience? Do you feel like you’ve been part of an activity that you would describe as an emergent behaviour?


Bonus material: Want to learn more about quorum sensing? This TED talk by Bonnie Bassler is a great intro.

One thought on “Emergence in communities – from quorum sensing in bacteria to human cohorts

  1. Pingback: URLs of wisdom – 16th July 2017 – Social in silico

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