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1.  Genetic Diversity among Botulinum Neurotoxin-Producing Clostridial Strains▿  
Journal of Bacteriology  2006;189(3):818-832.
Clostridium botulinum is a taxonomic designation for many diverse anaerobic spore-forming rod-shaped bacteria that have the common property of producing botulinum neurotoxins (BoNTs). The BoNTs are exoneurotoxins that can cause severe paralysis and death in humans and other animal species. A collection of 174 C. botulinum strains was examined by amplified fragment length polymorphism (AFLP) analysis and by sequencing of the 16S rRNA gene and BoNT genes to examine the genetic diversity within this species. This collection contained representatives of each of the seven different serotypes of botulinum neurotoxins (BoNT/A to BoNT/G). Analysis of the16S rRNA gene sequences confirmed previous identifications of at least four distinct genomic backgrounds (groups I to IV), each of which has independently acquired one or more BoNT genes through horizontal gene transfer. AFLP analysis provided higher resolution and could be used to further subdivide the four groups into subgroups. Sequencing of the BoNT genes from multiple strains of serotypes A, B, and E confirmed significant sequence variation within each serotype. Four distinct lineages within each of the BoNT A and B serotypes and five distinct lineages of serotype E strains were identified. The nucleotide sequences of the seven toxin genes of the serotypes were compared and showed various degrees of interrelatedness and recombination, as was previously noted for the nontoxic nonhemagglutinin gene, which is linked to the BoNT gene. These analyses contribute to the understanding of the evolution and phylogeny within this species and assist in the development of improved diagnostics and therapeutics for the treatment of botulism.
PMCID: PMC1797315  PMID: 17114256
2.  Growth of Pseudomonas mendocina on Fe(III) (Hydr)Oxides 
Applied and Environmental Microbiology  2001;67(10):4448-4453.
Although iron (Fe) is an essential element for almost all living organisms, little is known regarding its acquisition from the insoluble Fe(III) (hydr)oxides in aerobic environments. In this study a strict aerobe, Pseudomonas mendocina, was grown in batch culture with hematite, goethite, or ferrihydrite as a source of Fe. P. mendocina obtained Fe from these minerals in the following order: goethite > hematite > ferrihydrite. Furthermore, Fe release from each of the minerals appears to have occurred in excess, as evidenced by the growth of P. mendocina in the medium above that of the insoluble Fe(III) (hydr)oxide aggregates, and this release was independent of the mineral's surface area. These results demonstrate that an aerobic microorganism was able to obtain Fe for growth from several insoluble Fe minerals and did so with various growth rates.
PMCID: PMC93188  PMID: 11571141

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