Bacteria as Social Individuals
1 : Humboldt Universität zu Berlin
Bacteria have traditionally been seen as isolated individual cells. However, attention to social phenomena has led some to question this assumption. The suggestion is that because of widespread communal interactions bacteria should be conceived as multicellular individuals.
Although this novel perspective on bacterial individuality raises important questions about how microbial communities function, I claim it cannot supplant a cell-based approach. By distinguishing a physiological concept of individuality from an evolutionary one, I show that: a) in an evolutionary sense, individuality among social bacteria cannot be found at the group level; and b) in a physiological sense, bacterial groups have a relatively high degree of individuality, though not as high as paradigmatic cases of multicellularity.
Additionally, I argue that the debate on microbial individuality has been obscured by a failure to identify mechanisms that permit sociality to flourish. If sociality can be understood as altruism, and if mechanisms other than group selection explain altruism, there is no need to invoke group selection to explain sociality.
My conclusion is thus that bacterial communities have not crossed the analogue of the "Darwinian Threshold" envisioned for the transition from a soup of modular elements to lineage-forming, individual cells.
Although this novel perspective on bacterial individuality raises important questions about how microbial communities function, I claim it cannot supplant a cell-based approach. By distinguishing a physiological concept of individuality from an evolutionary one, I show that: a) in an evolutionary sense, individuality among social bacteria cannot be found at the group level; and b) in a physiological sense, bacterial groups have a relatively high degree of individuality, though not as high as paradigmatic cases of multicellularity.
Additionally, I argue that the debate on microbial individuality has been obscured by a failure to identify mechanisms that permit sociality to flourish. If sociality can be understood as altruism, and if mechanisms other than group selection explain altruism, there is no need to invoke group selection to explain sociality.
My conclusion is thus that bacterial communities have not crossed the analogue of the "Darwinian Threshold" envisioned for the transition from a soup of modular elements to lineage-forming, individual cells.
