Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 11/1/2005
Publication Date: 2/1/2007
Citation: Bacon, C.W., Hinton, D.M. 2007. Isolation, in planta detection, and uses of endophytic bacteria for plant protection. In: Hurst, C.J., Crawford, R.L., Garland, J.L., Lipson, D.A., Mills, A.L., Stetzenbach, L.D., editors. Manual of Environmental Microbiology. 3rd Edition. Washington, DC:ASM Press. p. 638-651. Interpretive Summary: There are several bacteria that permanently dwell within plants without doing harm. These bacteria, referred to as bacterial endophytes, live between cells, and never inside cell. These bacteria are the subject of current agricultural practices designed to protect plants from diseases and for various bacterial enhanced plant improvements. There is a large-scale hunt for bacteria that are endophyte and are capable of protecting plants. The declaration of a bacterium as an endophyte is based on its recovery from surface sterilized plant material and seed. However, this is very difficult since bacteria are also present in most of the plant’s environment, including on the outside. We review the current procedures useful to detect, measure, and evaluate bacterial endophytes for their use as biocontrol agents. Included in this review are the importance for adequate surface sterilizing, the importance of re-infecting the isolated bacteria into the plant, and the importance for comparisons made with the original endophyte-infected plants and noninfected plants, as well as other strains of the bacterium. This information will establish either the uniqueness of a strain as an endophyte or the uniqueness of endophytism within the species.
Technical Abstract: Endophytic bacteria are defined as those that dwell intercellularly in association with plants for most, if not all of their life cycles. These organisms are therefore symbiotic and are further distinguished in that the bacterium lives within the plant or portions of it as a nonpathogen although slight to moderate degrees of pathogenicity may be expressed. The declaration of a bacterium or fungus as an endophyte is based on its recovery from surface sterilized plant material and seed. Thus, endophytes are pragmatically defined, but there is one error inherent with this definition. Bacteria are often isolated from plant materials that have not been adequately surface sterilized, and the isolated bacterium not demonstrated to reside within the association by microscopic techniques. Successful detection of bacteria in plants is dependent upon a comprehensive procedure. In this review, techniques useful for the necessary dissections of the bacterial components from plant hosts to determine the physiological, biochemical and ecological contributions of bacteria to the intact association are complex are presented. We review endophytic bacteria, and outline procedures useful in establishing their presence, culture, physiological and metabolic interactions with host, and briefly discuss their biotechnological applications.