Global regulators key to bacterial adaptation on surfaces

A recent study published in PLOS Biology by Dr. Martin Ackermann and his team has shed light on the rapid evolution of surface-bound bacteria. The researchers found that mutations in key global regulators such as RicT, RNAse Y, and LexA trigger significant shifts in gene expression, influencing nearly half of all genes. This process ultimately shapes the bacteria's adaptive strategies for colonizing and expanding on surfaces.

The propensity of bacteria to adhere to surfaces and compete for space and resources is a fundamental aspect of microbial ecology. However, the specific mechanisms that drive bacterial evolution on surfaces have remained largely elusive. To address this gap, the research team conducted an evolution experiment focusing on distinct Bacilli populations under conditions favoring colony spreading. They observed a notable acceleration in the expansion rates of Bacillus subtilis colonies within a short period, with their radius expanding 2.5 times compared to their ancestors.

To further understand what drives this swift evolution, the researchers carried out a comprehensive analysis of the evolutionary changes in colony development. They identified mutations in several global regulators, including RicT, RNAse Y, and LexA. These mutations exhibited similar pleiotropic effects - they were found to decrease sporulation rates while concurrently facilitating colony expansion either by reducing extracellular polysaccharide production or promoting filamentous growth. High-throughput flow cytometry and gene expression profiling revealed that these regulatory mutations led to reproducible and parallel changes in global gene expression, impacting approximately 45% of all genes.

The study underscores the crucial role of global regulators as major pleiotropic hubs driving rapid surface adaptation in bacteria. These regulators coordinate parallel changes in colony composition and expansion, significantly reshaping gene expression patterns. While this coordinated activity generally fosters adaptation, Ackermann's team observed instances where it led to evolutionary divergence - underscoring the complexity of bacterial evolution on surfaces. Overall, these findings provide valuable insights into the molecular mechanisms underlying bacterial surface adaptation and evolution.

The research was conducted by Jordi van Gestel, et al., and is titled "Pleiotropic hubs drive bacterial surface competition through parallel changes in colony composition and expansion." It was published in PLoS Biology (2023). The DOI for the study is doi.org/10.1371/journal.pbio.3002338.