Extensive cellular multi-tasking within Bacillus subtilis biofilms.

Area of Science:

• Microbiology
• Systems Biology
• Bacterial Genetics

Background:

• Bacillus subtilis forms biofilms, complex communities crucial for survival.
• Within biofilms, cells exhibit diverse phenotypes, but the extent of this heterogeneity is poorly understood.
• Existing models may oversimplify cellular differentiation and task allocation in B. subtilis.

Purpose of the Study:

• To investigate the spatial organization and gene expression relationships of subpopulations in B. subtilis biofilms.
• To determine the extent of phenotypic heterogeneity and identify distinct cellular roles.
• To challenge and refine current models of cell differentiation in bacterial biofilms.

Main Methods:

• Creation of 182 B. subtilis strains with pairwise fluorescent transcriptional reporters for 14 key genes.
• Confocal microscopy to visualize the spatial distribution of gene expression within biofilms.
• Flow cytometry to quantify reporter co-expression and identify multi-tasking cells.

Main Results:

• Spatial mapping revealed distinct, sometimes co-localized, expression patterns for different genes within biofilms.
• Flow cytometry demonstrated significant co-expression, indicating many cells simultaneously perform multiple functions.
• Only a few subpopulations, like surfactin/plipastatin producers and sporulating/competent cells, showed distinct roles.

Conclusions:

• B. subtilis biofilms exhibit more complex cellular differentiation than previously modeled.
• The concept of cells specializing in single tasks is an oversimplification; many cells are multi-functional.
• These findings provide a framework for understanding microbial community dynamics and have implications for therapeutic strategies against bacterial infections.