Bacillus mojavensis: its endophytic nature, the surfactins and their role in the plant response to infection by Fusarium verticillioides

Authors: Bacon, Charles; Hinton, Dorothy

Submitted to: Bacteria in Agrobiology: Crop Ecosystems
Publication Type: Book / Chapter
Publication Acceptance Date: 1/15/2011
Publication Date: 5/12/2011
Citation: Bacon, C.W., Hinton, D.M. 2011. Bacillus mojavensis: its endophytic nature, the surfactins and their role in the plant response to infection by Fusarium verticillioides. In: Maheshwari, D.K., editors. Bacteria in Agrobiology: Plant Growth Responses. Berlin: Springer-Verlag. p. 21-39.

Interpretive Summary: Scientists in the Toxicology and Mycotoxin Research Unit were invited to contribute to a book dealing with the importance of bacteria in agronomic practices, particularly those dealing with plant growth. The bacteria reviewed by these scientists are those that are endophytic, i.e., those that dwell inside plants as natural inhabitants, where they promote plant growth and confer other important enhancements. These bacteria are plant friendly and offer a tremendous opportunity to control other disease organisms. These scientists reviewed the broad subject of bacterial endophytes, using one endophytic species, Bacillus mojavensis, to describe all the uses of this and other bacteria and their inhibitory substances used to control diseases. The work covered topics such as specific fungal inhibitors, the surfactins, discovered recently in B. mojavensis, by Unit scientists, and their various forms that are potential biocontrol for the pathogenic and mycotoxic fungal species, the endophytic Fusarium of corn and other cereals.

Technical Abstract: Bacterial endophytes are fundamentally important as natural components of most plants, wild and cultivated with strong ecological merits. These ancient associations are recently at the forefront of biological control strategies designed to circumvent the problems associated with pesticide uses, particularly on specific food crops. Bacterial endophytes form compatible associations that persist during the growing seasons, where several enhance benefits are associated, suggesting that such associations are mutualistic. Several genera of bacteria are known as root associations, and only recently are species being identified as plant endophytes, occupying the entire plant axis in most cases. Bacillus mojavensis was discovered in maize kernels and later determined to be an endophyte with biocontrol potential due to its inhibition of the maize mycotoxic and pathogenic fungus Fusarium verticillioides, itself an endophyte. It was subsequently shown that this strain and others were inhibitory to most fungi, especially pathogenic species. Further, maize plants infected with B. mojavensis showed a marked improvement in foliage and root growth and development, disease protection, and mycotoxin reduction. Components of B. mojavensis-infected maize are reviewed relative to biocontrol of F. verticillioides and other endophytic fungi. The patented and other strains of this bacterium were recently reported as producers of the lipopeptide biosurfactant Leu 7-surfactin. The chemistry, fermentation of the surfactins and their uses, along with the essential features of surfactins required for fungal inhibition are reviewed. We also review the host-parasite relations of this bacterial endophyte, and its biochemical utility in an effort to bring attention to the potential qualities of B. mojavensis, and other bacterial endophytes for enhancers of plant growth and protectors of diseases.