In situ control of root-bacteria interactions using optical trapping in transparent soil

Optical trapping of Pectobacterium atrosepticumquantifies factors affecting attachment of single cells on living root surfaces and identifies links between duration of contact and maintenance on the surface. Bacterial attachment on root surfaces is an important step preceding the colonization or internalization and subsequent infection of plants by pathogens. Unfortunately, bacterial attachment is not well understood because the phenomenon is difficult to observe. Here we assessed whether this limitation could be overcome using optical trapping approaches. We have developed a system based on counter-propagating beams and studied its ability to guide Pectobacterium atrosepticum (Pba) cells to different root cell types within the interstices of transparent soils. Bacterial cells were successfully trapped and guided to root hair cells, epidermal cells, border cells, and tissues damaged by laser ablation. Finally, we used the system to quantify the bacterial cell detachment rate of Pba cells on root surfaces following reversible attachment. Optical trapping techniques could greatly enhance our ability to deterministically characterize mechanisms linked to attachment and formation of biofilms in the rhizosphere.

Automated summary

Optical trapping techniques were used to quantify the factors affecting bacterial attachment on living root surfaces and determine the relationship between contact duration and maintenance on the surface. The system successfully guided Pectobacterium atrosepticum (Pba) cells to various root cell types, including root hair cells, epidermal cells, border cells, and laser-ablated tissues. This technique has the potential to enhance our understanding of attachment and biofilm formation mechanisms in the rhizosphere.