The significance of cell motility to microbial community morphogenesis

The morphologies of modern and fossil microbial communities are generated through many complex interactions between biological and environmental influences. Community morphology is thus a potential repository of valuable information about the processes involved in morphogenesis. It is this potential storage capacity of microbial community morphology that makes interpreting the microbialite fossil record desirable. However, extracting information about relevant biological and environmental processes from morphologies remains challenging.;This thesis presents a new conceptual framework for recognizing and elucidating connections between morphologies and specific biological behaviors. This framework represents a shift in perspective to a more biologically and process-centric mind-set. Utilizing this approach allows us to envision a new type of morphospace for microbial community morphology that is bounded by a detailed biological boundary. Cell motility is a widespread and common behavior that has emerged as a fundamental process influencing morphogenesis across all scales of microbial communities. Further, cell motility is the biological behavior that inspired and serves as an example of applying this framework. Also introduced here is the discovery that non-directed motility governs the genesis of complex reticulate morphologies in biofilms composed of a strain of the filamentous cyanobacteria, Pseudanabaena. Observations of this laboratory biofilm have improved our understanding of how the gliding and colliding of filamentous cells serves as a mechanism for morphogenesis, as well as of how environmental influences influence and overshadow this motility in morphogenesis. Filamentous cell motility also governs the genesis of complex reticulate morphologies in microbial mats in Pavilion Lake, British Columbia. The discovery and description of the Pavilion mats presented herein includes characterization of how motility influences both micro- and mesoscale microbial community structures. Identifying and characterizing the role of cell motility in morphogenesis sheds new light on the morphogenesis of microbial community morphology in both modern and ancient environments.