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Horizontal Gene Transfer May Involve Clostridium botulinum Neurotoxin Evolution
Author(s) -
Chang TzuuWang,
Singh Bal Ram
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a622-a
Subject(s) - biology , gene , genetics , horizontal gene transfer , clostridium botulinum , concerted evolution , codon usage bias , ribosomal rna , clostridium , molecular evolution , gene duplication , toxin , phylogenetic tree , bacteria , genome
Botulinum Neurotoxin (BoNT) is one of the most toxic substances with a mouse lethal dose of 0.3ng/kg and its toxicity on molar basis is 100 billion fold higher than sodium cyanide. Immunologically BoNT family has 7 different serotypes, BoNT/A to BoNT/G. BoNTs belong to a family Zn‐dependant endopeptidases that share similar active site (HELxH) and molecular structure (light chain and heavy chain). We have analyzed from the available public resources BoNT protein sequences to construct their relative genetic distances, and all the nucleotide sequences for dN/dS ratio calculation to determine the molecular evolution of BoNT. We have also determined the degree of sequence varation at the cleavage site of BoNT¡¦s neuronal substrates to estimate a possible co‐evolution relationship and pathogen‐host interaction strength by calculating the sequence entropy of cleavage sites. We have found that the molecular evolution tree of BoNT that is constructed by Jukes‐Cantor model and Neighbor‐Joining algorithm is quite different from the species tree of toxigenic Clostridia that was constructed based on 16S rRNA sequence alignment. The comparison of Codon Usage Frequency between the BoNT and other Clostridium boutlinum house keeping genes did not show significant statistical difference. So we believe that some horizontal gene transfer events may have occurred during the molecular evolution of BoNT and these events could be used to explain why the BoNT gene tree is not parallel to the evolutionary order of 16S rRNA tree of Clostridium botulinum. Similar codon usage frequency between BoNT and house keeping genes also suggests the expression of BoNT gene might be beneficial to the survival of the clostridial botulinum organisms. Supported in part by a DoD/Army Contract No. W911NF‐06‐1‐0095 and by the NIH through the New England Center of Excellence for Biodefense (Grant AI057159‐01).