Assessment Of Biochar As a Carrier For Plant Growth Promoting Strain Enterobacter Cloacae UW5.

The large-scale production of biochar for carbon sequestration provides an opportunity for using these materials to deliver plant-growth promoting rhizobacteria (PGPR) into agricultural soils. Prior research has shown that bacteria inoculated into biochar can survive for at least a one-year period. However, little is known about the fate of these bacteria once introduced into a soil, where predation and competition with indigenous bacteria often deplete inoculant populations. Here, we evaluated the suitability of a biochar produced from pinewood at a highest pyrolysis temperature of 300 °C as a carrier for an auxin-producing model PGPR strain, Enterobacter cloacae UW5. This strain was genetically modified to produce a green fluorescent protein marker that enabled tracking of the bacteria by fluorescence microscopy, selective plate counts, and quantitative PCR methods. The quantification of both total bacterial and UW5 populations after soil inoculation provided insight into the influence of biochar on native soil bacteria and inoculum survival. Furthermore, growth chamber experiments demonstrated that UW5 mobilized from biochar to colonize cucumber roots as well as the ability of UW5 to affect root branching, total root length, and plant size in the presence of biochar. Future studies will evaluate biochars with different physical and chemical properties for carrier suitability.