Microbial Adaptation
Adaptive divergence in Pseudomonas fluorescns
Environmental factors operating at the micro-pore scale in soil pore networks are expected to impact on the colonization, activity and fitness of the bacteria which inhabit these spaces (niches). Our understanding of these environments, obtained through direct measurement or from simulations of robust models, is rapidly increasing. However, our ability to undertake experiments to explicitly examine the fit between bacteria and their immediate environment needs to be developed.
We are approaching this problem using a combination of molecular microbiology and artificial microcosms. The genetic manipulation of model pseudomonads, such as the soil and rhizosphere-associated P. fluorescens SBW25, allows us to knock-out particular functions which may be important in colonization, activity or fitness. Isogenic pairs, comprising of the wild-type and mutant, can then compared in realistic soil microcosms in which pore structure, water distribution, oxygen and nutrient levels can be manipulated. These pairs can also be tested in far more simplified microcosms in which three dimensional structure and chemistry can be separately investigated.
Our current research includes investigating how the establishment of oxygen gradients impacts on SBW25 populations and drive the evolution of biofilm-forming strains; analyzing the cost-benefits of different types of SBW25 biofilm as a means of colonizing the air-liquid interface, how surfactant expression by soil Pseudomonas isolates might alter local water distribution at the micro-pore scale, and how the expression of cellulose by model Pseudomonas impacts on fitness and soil structure.