ARS | Publication request: MOLECULAR APPROACHES FOR ELUCIDATING THE IN SITU ACTIVITIES OF BIOLOGICAL CONTROL AGENTS AND THE NATURE OF BACTERIAL HABITATS IN THE RHIZOSPHERE

Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 31, 1997
Publication Date: N/A

Technical Abstract: Certain strains of bacteria suppress plant pathogenic bacteria and fungi in the rhizosphere through processes of resource competition or antibiosis. These processes are not likely to occur uniformly in time or space; instead, they undoubtedly take place only in those microhabitats where environmental factors favor their occurrence, and during periods in the bacterial life cycle when their genetic determinants are expressed. Molecular approaches are now available to assess the chemical nature of habitats that bacteria occupy in the rhizosphere, to determine if resource availability to microorganisms is influenced by their coinhabitants in the rhizosphere, and to assess the activities and physiological status of bacteria inhabiting the rhizosphere. A biological sensor constructed by fusing the ice nucleation reporter gene to an iron-regulated promoter has been useful in elucidating temporal alterations in iron availability to P. fluorescens in the rhizosphere. Reporter gene systems have also provided some of the first glimpses into signalling that occurs between bacterial coinhabitants of the rhizosphere. Recent evidence indicates that bacteria recognize compounds (i.e. N-acyl-homoserine lactone autoinducers or ferric-siderophore complexes) produced by their coinhabitants in the rhizosphere and respond through alterations in their own patterns of gene expression. Our understanding of communication that occurs between bacteria in natural habitats is yet undeveloped, but further studies investigating these phenomena promise to illuminate the importance of microbial community context in the activities of biological control agents.