A gene transfer agent and a dynamic repertoire of secretion systems hold the keys to the explosive radiation of the emerging pathogen Bartonella.
A gene transfer agent and a dynamic repertoire of secretion systems hold the keys to the explosive radiation of the emerging pathogen Bartonella.
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DOI：
10.1371/journal.pgen.1003393
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发表时间：
2013-03
期刊：
影响因子：
4.5
通讯作者：
Andersson SG
中科院分区：
文献类型：
--
作者：
Guy L;Nystedt B;Toft C;Zaremba-Niedzwiedzka K;Berglund EC;Granberg F;Näslund K;Eriksson AS;Andersson SG
基因转移剂（GTA）随机转移细菌基因组的短片段。最近在感染小鼠的细菌格拉哈姆巴尔通体中发现了一种新型推定的GTA。虽然GTA广泛存在于遗传多样性的细菌中，但它们在进化中的作用在很大程度上是未知的。在这里，我们提出了一个比较分析的16巴尔通体基因组的大小从1.4到2.6 Mb，包括6个新的基因组从巴尔通体分离牛，驼鹿，两只狗，和袋鼠。从428个正向核心基因推断的系统发育树表明，致命的人类病原体B。杆状菌与反刍动物适应性分支有关，而不是如先前所认为的是属中最早的分化物种。基因流分析确定了12个基因的GTA和噬菌体衍生的复制起点作为最保守的创新。这些位于几百kb的区域中，该区域还包含III、IV和V型分泌系统的基因簇的8个插入，以及脓分泌分子如霍乱样毒素的基因。这些基因表明，最近转移的7个基因在virB基因簇的IV型分泌系统从猫适应B。henselae到狗适应的B。vinsonii菌株我们表明，B。henselae GTA是功能性的，并且可以在体外转移基因。我们认为，GTA的维持是由选择驱动的，以增加水平基因转移的可能性，并认为这一过程是有益的，在人口水平上，通过促进适应性进化的主机适应系统，从而扩大主机范围的大小。这个过程会抵消基因丢失，并迫使所有细胞都参与GTA和分泌分子的产生。这些结果推进了我们对GTA在细菌基因组进化中所起作用的理解。病毒是自私的遗传元件，复制和转移自己的DNA，通常在这个过程中杀死宿主细胞。与病毒不同，基因转移剂（GTA）转移的是细菌基因组的随机片段，而不是它们自己的DNA。GTA广泛存在于细菌基因组中，但尚不清楚它们是否对细菌有益。在这项研究中，我们使用新出现的病原体巴尔通体作为我们的模型来研究GTA的进化。我们对6个巴尔通体分离株的基因组进行了测序，其中包括从瑞典野生驼鹿中分离的两个新菌株。使用比较基因组学方法，我们在最后一个共同祖先中寻找创新，这些创新可以帮助解释该属的爆炸性辐射。令人惊讶的是，我们发现GTA和噬菌体衍生的复制起点的基因簇是最保守的创新，表明强选择性约束。我们认为，GTA的显着稳定性的原因是，它提供了一种机制，复制和重组基因的分泌系统。这导致了对广泛宿主的适应性。
Gene transfer agents (GTAs) randomly transfer short fragments of a bacterial genome. A novel putative GTA was recently discovered in the mouse-infecting bacterium Bartonella grahamii. Although GTAs are widespread in phylogenetically diverse bacteria, their role in evolution is largely unknown. Here, we present a comparative analysis of 16 Bartonella genomes ranging from 1.4 to 2.6 Mb in size, including six novel genomes from Bartonella isolated from a cow, two moose, two dogs, and a kangaroo. A phylogenetic tree inferred from 428 orthologous core genes indicates that the deadly human pathogen B. bacilliformis is related to the ruminant-adapted clade, rather than being the earliest diverging species in the genus as previously thought. A gene flux analysis identified 12 genes for a GTA and a phage-derived origin of replication as the most conserved innovations. These are located in a region of a few hundred kb that also contains 8 insertions of gene clusters for type III, IV, and V secretion systems, and genes for putatively secreted molecules such as cholera-like toxins. The phylogenies indicate a recent transfer of seven genes in the virB gene cluster for a type IV secretion system from a cat-adapted B. henselae to a dog-adapted B. vinsonii strain. We show that the B. henselae GTA is functional and can transfer genes in vitro. We suggest that the maintenance of the GTA is driven by selection to increase the likelihood of horizontal gene transfer and argue that this process is beneficial at the population level, by facilitating adaptive evolution of the host-adaptation systems and thereby expansion of the host range size. The process counters gene loss and forces all cells to contribute to the production of the GTA and the secreted molecules. The results advance our understanding of the role that GTAs play for the evolution of bacterial genomes. Viruses are selfish genetic elements that replicate and transfer their own DNA, often killing the host cell in the process. Unlike viruses, gene transfer agents (GTAs) transfer random pieces of the bacterial genome rather than their own DNA. GTAs are widespread in bacterial genomes, but it is not known whether they are beneficial to the bacterium. In this study, we have used the emerging pathogen Bartonella as our model to study the evolution of GTAs. We sequenced the genomes of six isolates of Bartonella, including two new strains isolated from wild moose in Sweden. Using a comparative genomics approach, we searched for innovations in the last common ancestor that could help explain the explosive radiation of the genus. Surprisingly, we found that a gene cluster for a GTA and a phage-derived origin of replication was the most conserved innovation, indicative of strong selective constraints. We argue that the reason for the remarkable stability of the GTA is that it provides a mechanism to duplicate and recombine genes for secretion systems. This leads to adaptability to a broad range of hosts.
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影响因子：
10.7
作者：
Castresana, J
通讯作者：
Castresana, J
DOI：
10.1073/pnas.0400975101
发表时间：
2004-06-29
影响因子：
11.1
作者：
Boussau, B;Karlberg, EO;Andersson, SGE
通讯作者：
Andersson, SGE
宿主适应性基因的径流复制与小鼠感染Bartonella grahamii基因组中的基因转移剂有关。
影响因子：
4.5
作者：
Berglund EC;Frank AC;Calteau A;Vinnere Pettersson O;Granberg F;Eriksson AS;Näslund K;Holmberg M;Lindroos H;Andersson SG
通讯作者：
Andersson SG
影响因子：
9.4
作者：
BRENNER, DJ;OCONNOR, SP;STEIGERWALT, AG
通讯作者：
STEIGERWALT, AG
影响因子：
4.9
作者：
Berglund, Eva C.;Ellegaard, Kirsten;Andersson, Siv G. E.
通讯作者：
Andersson, Siv G. E.