DIVERSITY OF THEBURKHOLDERIA CEPACIACOMPLEX ANDIMPLICATIONS FORRISKASSESSMENT OFBIOLOGICALCONTROLSTRAINS

Abstract

The Burkholderia cepacia complex (Bcc) consists of several species of closely related and extremely versatile gram-negative bacteria found naturally in soil, water, and the rhizosphere of plants. Strains of Bcc have been used in biological control of plant diseases and bioremediation, while some strains are plant pathogens or opportunistic pathogens of humans with cystic fibrosis. The ecological versatility of these bacteria is likely due to their unusually large genomes, which are often comprised of several (typically two or three) large replicons, as well as their ability to use a large array of compounds as sole carbon sources. The original species B. cepacia has been split into eight genetic species (genomovars), including five named species, but taxonomic distinctions have not enabled biological control strains to be clearly distinguished from human pathogenic strains. This has led to a reassessment of the risk of several strains registered by the U.S. Environmental Protection Agency for biological control. We review the biology of Bcc bacteria, especially how our growing knowledge of Bcc ecology and pathogenicity might be used in risk assessment. The capability of this bacterial complex to cause disease in plants and humans, as well as to control plant diseases, affords a rare opportunity to explore traits that may function in all three environments.

Taxon K, a complex within the Burkholderia cepacia complex, comprises at least two novel species, Burkholderia contaminans sp. nov. and Burkholderia lata sp. nov.

“…The organisms can be exploited for biocontrol, bioremediation and plant-growth-promotion purposes, but their capacity as opportunistic bacteria to cause human infections, in particular in cystic fibrosis patients, hampers their use in these biotechnological applications (Parke & Gurian-Sherman, 2001). The taxonomy of the Bcc has evolved dramatically in the last few years .…”

Burkholderia latens sp. nov., Burkholderia diffusa sp. nov., Burkholderia arboris sp. nov., Burkholderia seminalis sp. nov. and Burkholderia metallica sp. nov., novel species within the Burkholderia cepacia complex

“…Some Bcc strains are recognized for their beneficial properties as plant-growth promoters, bioremediators and biocontrol strains (Parke & Gurian-Sherman, 2001), whereas others are notorious as pathogens causing infections in plants and immunocompromised individuals such as cystic fibrosis patients (Coenye & Vandamme, 2003;Mahenthiralingam et al, 2005).…”

Multiscale responses of microbial life to spatial distance and environmental heterogeneity in a patchy ecosystem

“…Here, we examined the relative contributions of SD and EH to genetic relatedness and abundance of the Burkholderia cepacia complex (BCC) and one of the dominant species of that complex, Burkholderia ambifaria, which is a cosmopolitan, soil-borne, free-living bacterium often associated with soil roots (16). The genomic relatedness of individual bacterial colonies was determined in a spatially explicit sampling scheme across a patchy agricultural landscape spanning a total area of 250 ϫ 150 m. Environmental heterogeneity consisted of varying soil physical and chemical properties and of predefined patches of four homogenous plant species.…”