Spatial variation in Bacillus thuringiensis/ cereus populations within the phyllosphere of broad-leaved dock ( Rumex obtusifolius) and surrounding habitats

• Published in: FEMS microbiology ecology Vol. 54; no. 3; pp. 417 - 425
• Main Authors: Collier, Fay A., Elliot, Sam L., Ellis, Richard J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Elsevier B.V 01.11.2005; Blackwell Publishing Ltd; Blackwell; Oxford University Press
• Subjects: Bacillus cereus - metabolism; Bacillus cereus - physiology; Bacillus thuringiensis; Bacillus thuringiensis - metabolism; Bacillus thuringiensis - physiology; Bacterial Toxins - genetics; Bacterial Toxins - metabolism; Biological and medical sciences; Cluster Analysis; cry Genes; DNA Primers; Ecological function; Ecological monitoring; Ecology; Electrophoresis, Agar Gel; Fundamental and applied biological sciences. Psychology; Genes; Genes, Bacterial - genetics; Grasses; Leaves; Lognormal distribution; Microbiology; Normal distribution; Phyllosphere; Phylogeny; Plant Leaves - microbiology; Plasmids; Polymerase Chain Reaction; Population Density; Populations; Rumex; Rumex obtusifolius; Sampling; Selective media; Soil Microbiology; Soils; Spatial variation; United Kingdom; World; cry Genes; Spatial variation; Bacillus thuringiensis; Lognormal distribution; Genes; Shock; Prevalence; Microbiology; Rumex obtusifolius; Samplings; Bacillaceae; Epidemiology; Bacillus cereus; Bacillales; Gene; Dicotyledones; Angiospermae; Phyllosphere; Bacteria; Weed; Polygonaceae; Plasmid; Polymerase chain reaction; Soils; Toxin; Isolate; Spermatophyta
• ISSN: 0168-6496; 1574-6941
• DOI: 10.1016/j.femsec.2005.05.005

The aim of this study was to determine the prevalence and toxin gene diversity of Bacillus thuringiensis/B. cereus in the phyllosphere of broad-leaved dock ( Rumex obtusifolius) at a small spatial scale. B. thuringiensis/ cereus populations were isolated from the phyllosphere of dock and neighbouring grass and in neighbouring soil using commercially available selective media which avoided the disadvantageous heat-shock selection procedure. The maximum density of B. thuringiensis/ cereus in the dock phyllosphere was 1.9 × 10 4 CFU g −1 but the between-leaf variation in numbers was found to follow a lognormal distribution. B. thuringiensis/ cereus was also found at significant densities in soil and the phyllosphere of grass adjacent to the dock plants. PCR screening indicated that genes encoding cry1 toxin were present in the plasmids of 36.9% of B. thuringiensis/ cereus isolates tested, 11.9% contained cry2, and none of the dock leaf isolates tested contained cry3, cry4, cry7 or cry8 genes. The diversity of cry genes is similar to that found from other studies focused on other parts of the world. This work is the first concerning the prevalence of B. thuringiensis/ cereus on leaves in the UK, finding population sizes of previously unrecorded levels and a greater relative proportion of B. thuringiensis. We have also illustrated that before any ecological function can be investigated, suitable sampling scales need to be considered – here we have shown that the minimum sampling unit should be individual leaves, to account for the log-normal distribution.