Recombination and insertion events involving the botulinum neurotoxin complex genes in Clostridium botulinum types A, B, E and F and Clostridium butyricum type E strains
Recombination and insertion events involving the botulinum neurotoxin complex genes in Clostridium botulinum types A, B, E and F and Clostridium butyricum type E strains
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DOI：
10.1186/1741-7007-7-66
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发表时间：
2009-10-05
期刊：
影响因子：
5.4
通讯作者：
Detter, John C.
中科院分区：
文献类型：
--
作者：
Hill, Karen K.;Xie, Gary;Detter, John C.
背景资料：肉毒梭菌是至少四种不同物种的分类学名称，其通过表达七种不同C中的一种（单价）或两种（二价）来定义。肉毒杆菌神经毒素（BoNT，A-G）。这4种植物被分类为C. I-IV型肉毒杆菌。在不同类群的菌株中bont基因的存在可能是毒素操纵子在种间水平转移的结果。代表A、B、E和F血清型的肉毒杆菌菌株和C.丁酸菌E型菌株进行比较，以检查它们的基因组组织或共线性，以及肉毒杆菌毒素复合物基因的位置。这些比较确定了蛋白水解（组I）菌株或nonproteolytic（组II）菌株之间的同线性，但不是两组之间。检测的菌株中的bont复合体基因不是随机定位的，而是在染色体的三个区域或质粒内的两个特定位点中发现的。来自Bf菌株的序列的比较揭示了与质粒pCLJ的同源性，其中bont/bv B基因具有相似的位置，但bont/a4基因被bont/f基因取代。对毒素簇基因的分析表明，发生了许多重组事件，包括ntnh基因内的几个事件。一个这样的重组事件导致bont/a1基因整合到血清型毒素B ha簇中，导致通常与食源性肉毒中毒爆发相关的成功谱系。In C. E型和C型肉毒杆菌。在丁酸菌E型菌株中，bont/e基因簇的位置似乎是插入事件的结果，该插入事件在两个物种中独立地在相同位置分裂rarA（重组相关基因）。对代表不同菌株的基因组序列的分析揭示了插入序列（IS）元件和其他转座子的存在。相关的蛋白质，如重组酶，其可以促进bont的水平转移;除了毒素复合物基因之间的重组之外，这些事件导致了今天在产生神经毒素的梭菌中观察到的谱系。
Background: Clostridium botulinum is a taxonomic designation for at least four diverse species that are defined by the expression of one (monovalent) or two (bivalent) of seven different C. botulinum neurotoxins (BoNTs, A-G). The four species have been classified as C. botulinum Groups I-IV. The presence of bont genes in strains representing the different Groups is probably the result of horizontal transfer of the toxin operons between the species.Results: Chromosome and plasmid sequences of several C. botulinum strains representing A, B, E and F serotypes and a C. butyricum type E strain were compared to examine their genomic organization, or synteny, and the location of the botulinum toxin complex genes. These comparisons identified synteny among proteolytic (Group I) strains or nonproteolytic (Group II) strains but not between the two Groups. The bont complex genes within the strains examined were not randomly located but found within three regions of the chromosome or in two specific sites within plasmids. A comparison of sequences from a Bf strain revealed homology to the plasmid pCLJ with similar locations for the bont/bv b genes but with the bont/a4 gene replaced by the bont/f gene. An analysis of the toxin cluster genes showed that many recombination events have occurred, including several events within the ntnh gene. One such recombination event resulted in the integration of the bont/a1 gene into the serotype toxin B ha cluster, resulting in a successful lineage commonly associated with food borne botulism outbreaks. In C. botulinum type E and C. butyricum type E strains the location of the bont/e gene cluster appears to be the result of insertion events that split a rarA, recombination-associated gene, independently at the same location in both species.Conclusion: The analysis of the genomic sequences representing different strains reveals the presence of insertion sequence (IS) elements and other transposon-associated proteins such as recombinases that could facilitate the horizontal transfer of the bonts; these events, in addition to recombination among the toxin complex genes, have led to the lineages observed today within the neurotoxin-producing clostridia.