Rickard Lab

https://sph.umich.edu/faculty-profiles/rickard-alexander.html
The focus of the Rickard research group is to elucidate the underlying mechanisms that promote multi-species biofilm development. To achieve this, the focus of our research is on natural multi-species biofilm communities and the interactions between the component species under environmentally germane conditions. Such studies are arguably important because real-world recently isolated wild-type bacteria behave differently in as compared to well-used domesticated laboratory strains. In addition, we tend to use media in which bacteria normally grow. For example, we use saliva for dental plaque biofilm studies.

Recent studies indicate that inter-species communication is essential for the ordered successional integration of bacteria into biofilms. This process is required for establishing juxtaposition between different species and may promote cooperation between species within a biofilm. Interspecies communication can be through two key mechanisms:
  • Coaggregation interactions between genetically distinct species.
  • Chemical signaling within and between between species.
Both these processes have been identified as occurring between bacteria in the natural environment and between bacteria that are part of the human microbial flora. Furthermore, evidence is emerging that synergy between coaggregation and signaling may occur. In these instances it is hypothesized that coaggregation brings species in close proximity and thus exposes the bacteria to elevated concentrations of signal molecules. These signals can be metabolites or small diffusible molecules such as Autoinducer-2.

Using an array of physiological, ecological and molecular techniques in combination with biofilms developed in vivo and in vitro, it is our goal to understand the regulation of the multi-species biofilm phenotype and how this alters (or is altered by) the ecology of the biofilm. The ecology if the biofilm will dictate the potential of the biofilm community to promote health or be problematic and/or cause disease.

Bacteria seldom exist as free floating solitary cells. In most environments they live in association with surfaces as part of multi-species biofilms. From freshwater environments to marine systems to the human oral cavity, these communities exhibit properties that are distinct from free floating cells. As such, the amalgamation of different species within these communities can:
  • Enhance antimicrobial resistance.
  • Promote the breakdown and corrosion of surfaces.
  • Possess enhanced growth and altered phenotypic characteristics through metabolic communication and the production of small diffusible signaling molecules.
  • Collectively, promote or hinder the integration of pathogenic or problematic fungal or bacterial species.
How different species adhere to one another, communicate with one another and grow as a unified community is critical to understanding how to control these communities.


The aim of my laboratory is to understand the dynamics that promote the development and regulation of multi-species biofilm communities. Such an understanding will contribute to the development of novel and improved strategies to control biofilm communities and promote human health.