Bacterial Populations as Multicellular Organisms

Kathy Lee

INTRODUCTION

•1998 … Scientific American – “Bacteria as Multicellular Organisms”

•Multicellularity- only considered a specialized adaptive strategy

•Today

CORE CONCEPTS OF BACTERIAL MULTICELLULARITY

1.Communication and

decision-making capabilities 2.Examples of communication

and behaviors3.Derive adaptive benefits

INTERCELLULAR COMMUNICATION

•Diverse Classes of Signal Molecules –AHL signaling–Oligopeptides

•Differences between AHL signaling and Oligopeptides

•Not all the small diffusible molecules are signals

•Highly diversified chemical structures

Signal Response Systems: Interpreting Chemical Messages in an Informationally Rich Environment•Each cell can make an appropriate

decision and adjust its activity•Myxobacteria and Bacillus – two

good examples of complex signal-processing networks

•Complexities will prove to be typical

COORDINATED MULTICELLULAR BEHAVIORS – A GENERAL BACTERIAL TRAIT

•Bacteria differentiate biochemically and morphologically and their interactions

•Colony development and collective motility phenomena in bacteria

–E.coli Colony Development•Cell-cell interactions occur after the first cell division

–B. subtilis Colony Development –Proteus and Serratia Swarming

•“Swarming” is the process of rapid migration over a surface

–Granule Development in Anaerobic Bioreactors •Microbial Consortia

ADAPTIVE BENEFITS FROM MULTICELLULAR COOPERATION

•More efficient proliferation from cellular division

•Access to resources and niches that require a critical mass and cannot effectively be utilized by isolated cells

•Collective defense against antagonists that eliminate isolated cells

Optimization of population survival by differentiation into distinct cell types

•Sporulation and Formation of Dormant Cells

•Exchange of Genetic Information

•Mutation

CONCLUSION

•Bacterial multicellularity deepens our appreciation of the information-processing capabilities of individual bacterial cells.