A CRISPR interference screen reveals a role for cell wall teichoic acids in conjugation inBacillus subtilis

Summary Conjugative elements are widespread in bacteria and include plasmids and integrative and conjugative elements (ICEs). They transfer from donor to recipient cells via an element-encoded type IV secretion system. These elements interact with and utilize host functions for their lifecycles. We sought to identify essential host genes involved in the lifecycle of the integrative and conjugative element ICE Bs1 of Bacillus subtilis . We constructed a library of strains for inducible knockdown of essential B. subtilis genes using CRISPR interference. Each strain expressed one guide RNA in ICE Bs1 . We induced partial interference of essential genes and identified those that caused an acute defect in acquisition of ICE Bs1 by recipient cells. This screen revealed that reducing expression of genes needed for synthesis of cell wall teichoic acids caused a decrease in conjugation. Using three different ways to reduce their synthesis, we found that wall teichoic acids were necessary in both donors and recipients for efficient conjugative transfer of ICE Bs1 . Further, we found that depletion of wall teichoic acids caused cells involved in ICE Bs1 conjugation to die, most likely from damage to the cell envelope. Our results indicate that wall teichoic acids help protect against envelope stress caused by an active conjugation machinery.