It has recently been proposed, but not proven, that bacteria associated with plant roots may produce the volatile hydrocarbon, isoprene, as a protective mechanism. Isoprene might act to repel organisms that feed on these bacteria or the host roots. The work presented here is an initial test of th... Show moreIt has recently been proposed, but not proven, that bacteria associated with plant roots may produce the volatile hydrocarbon, isoprene, as a protective mechanism. Isoprene might act to repel organisms that feed on these bacteria or the host roots. The work presented here is an initial test of this idea, aiming to determine if isoprene-producing bacteria are common in the rhizosphere (the region in which living plant roots and micro-organisms interact). Bacteria associated with beet (Beta vulgaris) roots were isolated by culturing the soil adhering to the peel. All isolates were screened for isoprene emission and other phenotypic characteristics. Isoprene emission was detected by an isothermal (64° C) gas chromatography system. All 96 isolates produced some isoprene and a small percentage (28%) of isolates were very-high or high isoprene emitters. These results show that isoprene-producing bacteria are common in the beet rhizosphere. Identity tests of the 13 very-high isoprene emitters revealed much diversity. The phenotypic characteristics tested included Gram positive/negative cell surface, thermotolerance, fluorescent pigment, catalase production and spore formation. These results suggest that the very-high isoprene emitters in the beet rhizosphere are Gram-negative and not Gram-positive genera as well as all being catalase positive. Initial attempts to use the Polymerase Chain Reaction (PCR) to identify unknown isolates are described. Use of the PCR and further quantification of isoprene-producing bacteria will identify and improve understanding of the role of isoprene in the rhizosphere. This Show less
