Bacterial Microcolonies in Gel Beads for High-throughput Screening.

Area of Science:

• Microbiology
• Biotechnology
• Molecular Biology

Background:

• High-throughput screening is essential for identifying rare functional variants in bacterial populations.
• Directed evolution, synthetic biology, and deep mutational scanning rely on efficient screening methods.
• Existing methods face challenges with cell-to-cell variability and sensitivity.

Purpose of the Study:

• To describe a novel protocol for high-throughput screening of bacterial microcolonies within gel beads.
• To enable efficient isolation and analysis of rare bacterial mutants with desired properties.
• To improve sensitivity and reduce variability in screening compared to single-cell sorting.

Main Methods:

• Encapsulation of single E. coli cells into monodisperse water-in-oil emulsion droplets using microfluidics.
• Formation of gel beads containing monoclonal microcolonies through agarose solidification.
• Isolation, sorting via fluorescence-activated cell sorting (FACS), and recovery of bacteria from gel beads.

Main Results:

• The protocol successfully enables the growth of microcolonies within gel beads for screening.
• Sorting of microcolonies by FACS based on fluorescent reporter expression was demonstrated.
• Measuring average microcolony fluorescence improved sensitivity and reduced phenotypic variability.

Conclusions:

• This gel bead microcolony screening method offers a sensitive and robust approach for identifying rare functional bacterial variants.
• The protocol is applicable to various applications, including directed evolution and deep mutational scanning.
• The method enhances screening efficiency by averaging signals and reducing cell-to-cell variability.