Lazy but efficient

According to the Black Queen Hypothesis (BQH), functions, which are essential, costly and leaky, bring about organisms that lose the encoding genes and profit from the work of others. To test whether the BQH applies to pesticide degradation, Billet et al. (2019) chose four genera of bacteria involved in atrazine degradation. The authors decided to perform culture-based experiments in addition to multiplex PCR. The loss of atrazine degrading genes after ~100 generations in cultures without atrazine established the high cost of expressing this function. In cultures with atrazine as the only nitrogen source, atrazine mineralisation became more efficient. Quantification of colony forming units in all possible combinations of co- and monocultures revealed strong dependence of three species on the fourth. Multiplex PCR further evidenced a loss of key genes in these species. Interestingly, one of the dependent species slightly buffered the negative impact on the public goods provider.

This study provides remarkable insight into microbial evolution and ecology within the conceptual framework of the BQH. The results suggest that microbial assemblages are more effective at degrading pesticides, even though one microbe does the bulk of the work. This insight has implications for the usage of microbes in bioremediation projects.

Billet, L., Devers, M., Rouard, N., Martin-Laurent, F. & Spor, A. (2019). Labour sharing promotes coexistence in atrazine degrading bacterial communities. Scientific Reports, 9(1), 18363.