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首页> 外文期刊>Infection and immunity >Insertional Inactivation of Genes Responsible for thed-Alanylation of Lipoteichoic Acid inStreptococcus gordonii DL1 (Challis) Affects Intrageneric Coaggregations
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Insertional Inactivation of Genes Responsible for thed-Alanylation of Lipoteichoic Acid inStreptococcus gordonii DL1 (Challis) Affects Intrageneric Coaggregations

机译：戈登链球菌DL1（Challis）中脂磷壁酸d-丙二酸负责基因的插入失活影响基因内聚集。

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Most human oral viridans streptococci participate in intrageneric coaggregations, the cell-to-cell adherence among genetically distinct streptococci. Two genes relevant to these intrageneric coaggregations were identified by transposon Tn916 mutagenesis ofStreptococcus gordonii DL1 (Challis). A 626-bp sequence flanking the left end of the transposon was homologous todltA and dltB of Lactobacillus rhamnosus ATCC 7469 (formerly called Lactobacillus casei). A 60-kb probe based on this flanking sequence was used to identify the homologous DNA in a fosmid library of S. gordonii DL1. This DNA encodedd-alanine-d-alanyl carrier protein ligase that was expressed in Escherichia coli from the fosmid clone. The cloned streptococcal dltA was disrupted by inserting anermAM cassette, and then it was linearized and transformed into S. gordonii DL1 for allelic replacement. Erythromycin-resistant transformants containing a single insertion indltA exhibited a loss of d-alanyl esters in lipoteichoic acid (LTA) and a loss of intrageneric coaggregation. This phenotype was correlated with the loss of a 100-kDa surface protein reported previously to be involved in mediating intrageneric coaggregation (C. J. Whittaker, D. L. Clemans, and P. E. Kolenbrander, Infect. Immun. 64:4137–4142, 1996). The mutants retained the parental ability to participate in intergeneric coaggregation with human oral actinomyces, indicating the specificity of the mutation in altering intrageneric coaggregations. The mutants were altered morphologically and exhibited aberrant cell septa in a variety of pleomorphs. The natural DNA transformation frequency was reduced 10-fold in these mutants. Southern analysis of chromosomal DNAs from various streptococcal species with the dltA probe revealed the presence of this gene in most viridans streptococci. Thus, it is hypothesized that d-alanyl LTA may provide binding sites for the putative 100-kDa adhesin and scaffolding for the proper presentation of this adhesin to mediate intrageneric coaggregation.
机译：大多数人类口腔翠绿链球菌参与基因内共聚集，即遗传上不同的链球菌之间的细胞间粘附。通过戈登链球菌DL1（Challis）的转座子Tn 916 诱变鉴定出与这些内部共聚相关的两个基因。转座子左端的626bp序列与鼠李糖乳杆菌ATCC 7469的 dltA 和 dltB 同源（以前称为干酪乳杆菌）。基于该侧翼序列的60-kb探针用于鉴定 S的fosmid文库中的同源DNA。 gordonii DL1。该DNA编码的丙氨酸-d-丙氨酰载体蛋白连接酶在fosmid克隆的大肠杆菌中表达。通过插入 ermAM 盒破坏克隆的链球菌 dltA ，然后将其线性化并转化为 S。 gordonii DL1用于等位基因替换。包含单个插入 dltA 的红霉素抗性转化子在脂磷壁酸（LTA）中失去了d-丙氨酸酯，并且失去了内部共聚。该表型与先前报道的参与介导基因内共聚的100kDa表面蛋白的损失有关（C. J. Whittaker，D. L. Clemans和P. E. Kolenbrander，Infect。Immun。64：4137-4142，1996）。突变体保留了亲本与人类口腔放线菌参与基因间共聚合的能力，表明突变在改变基因内共聚合中的特异性。突变体在形态上发生了改变，并在多种多形体中表现出异常的细胞间隔。在这些突变体中，天然DNA转化频率降低了10倍。使用 dltA 探针对各种链球菌物种的染色体DNA进行Southern分析，结果表明该基因存在于大多数vi虫链球菌中。因此，假设d-丙氨酰LTA可为推定的100-kDa粘附素和支架提供结合位点，以适当地呈递该粘附素以介导遗传内共聚集。

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