The potential for gene exchange between rhizosphere bacteria

Abstract

The soil as such provides little available carbon and energy to microorganisms and therefore heterotrophic microbial activity in soil is dependent on carbon and energy inputs from the plant. The primary production is therefore from photosynthesis but up to 40% or even more of the plant’s total photosynthate can be released by roots in the form of exudates, lysates, mucilage, sloughed-off cells (including root cap cells) and respiratory C0₂.^1–3 Such carbon flow has been investigated by growing plants exclusively on a source of uniformly-labelled ¹⁴CO₂ in a sealed plant growth chamber, with the roots sealed in an aerated pot. Because the rhizosphere organisms rapidly utilize the substrates, much of the carbon appears as CO₂ which can be trapped from the gas effluent from the pot. As the roots age and senesce, the whole root system becomes available for microbial degradation, as do the residues of the shoot tissue eventually.