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首页> 外文期刊>BMC Genomics >Comparative genome analysis of Streptococcus infantarius subsp. infantarius CJ18, an African fermented camel milk isolate with adaptations to dairy environment
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Comparative genome analysis of Streptococcus infantarius subsp. infantarius CJ18, an African fermented camel milk isolate with adaptations to dairy environment

机译：婴儿链球菌亚种的比较基因组分析。 infantarius CJ18，一种适应乳业环境的非洲发酵骆驼奶分离株

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Background Streptococcus infantarius subsp. infantarius (Sii) belongs to the Streptococcus bovis/Streptococcus equinus complex associated with several human and animal infections. Sii is a predominant bacterium in spontaneously fermented milk products in Africa. The genome sequence of Sii strain CJ18 was compared with that of other Streptococcus species to identify dairy adaptations including genome decay such as in Streptococcus thermophilus, traits for its competitiveness in spontaneous milk fermentation and to assess potential health risks for consumers. Results The genome of Sii CJ18 harbors several unique regions in comparison to Sii ATCC BAA-102T, among others an enlarged exo- and capsular polysaccharide operon; Streptococcus thermophilus-associated genes; a region containing metabolic and hypothetical genes mostly unique to CJ18 and the dairy isolate Streptococcus gallolyticus subsp. macedonicus; and a second oligopeptide transport operon. Dairy adaptations in CJ18 are reflected by a high percentage of pseudogenes (4.9%) representing genome decay which includes the inactivation of the lactose phosphotransferase system (lacIIABC) by multiple transposases integration. The presence of lacS and lacZ genes is the major dairy adaptation affecting lactose metabolism pathways also due to the disruption of lacIIABC. We constructed mutant strains of lacS, lacZ and lacIIABC and analyzed the resulting strains of CJ18 to confirm the redirection of lactose metabolism via LacS and LacZ. Natural competence genes are conserved in both Sii strains, but CJ18 contains a lower number of CRISPR spacers which indicates a reduced defense capability against alien DNA. No classical streptococcal virulence factors were detected in both Sii strains apart from those involved in adhesion which should be considered niche factors. Sii-specific virulence factors are not described. Several Sii-specific regions encoding uncharacterized proteins provide new leads for virulence analyses and investigation of the unclear association of dairy and clinical Sii with human diseases. Conclusions The genome of the African dairy isolate Sii CJ18 clearly differs from the human isolate ATCC BAA-102T. CJ18 possesses a high natural competence predisposition likely explaining the enlarged genome. Metabolic adaptations to the dairy environment are evident and especially lactose uptake corresponds to S. thermophilus. Genome decay is not as advanced as in S. thermophilus (10-19%) possibly due to a shorter history in dairy fermentations.
机译：背景婴儿链球菌亚种。婴儿（Sii）属于牛链球菌/马链球菌复合体，与几种人类和动物感染有关。 Sii是非洲自发发酵乳制品中的主要细菌。将Sii菌株CJ18的基因组序列与其他链球菌物种的基因组序列进行比较，以鉴定乳制品适应性变化，包括诸如嗜热链球菌中的基因组衰变，其在自发性牛奶发酵中的竞争力特征以及评估消费者的潜在健康风险。结果与Sii ATCC BAA-102 T 相比，Sii CJ18的基因组具有几个独特的区域，其中包括一个扩大的胞外和荚膜多糖操纵子。嗜热链球菌相关基因;该区域包含的代谢基因和假设基因大部分仅对CJ18和乳制品分离物鸡溶链球菌亚种具有独特性。马其顿;第二个寡肽转运操纵子。代表基因组衰退的假基因的高百分比（4.9％）反映了CJ18中乳制品的适应性变化，其中包括通过多种转座酶整合使乳糖磷酸转移酶系统（lacIIABC）失活。 lacS和lacZ基因的存在是影响乳糖代谢途径的主要乳制品适应方法，也是由于lacIIABC的破坏。我们构建了lacS，lacZ和lacIIABC突变菌株，并分析了所得的CJ18菌株，以确认通过LacS和LacZ进行乳糖代谢的重定向。天然能力基因在两个Sii菌株中均保守，但CJ18含有较少数量的CRISPR间隔子，这表明其对外来DNA的防御能力降低。除了那些被认为是小生境因素的粘着菌，在这两个Sii菌株中均未检测到经典的链球菌致病因子。没有描述Sii特异性毒力因子。几个编码Sii的未编码蛋白质的Sii特异区域为毒力分析和乳品和临床Sii与人类疾病的不清楚关联提供了新的线索。结论非洲乳品分离株Sii CJ18的基因组明显不同于人分离株ATCC BAA-102 T 。 CJ18具有很高的自然能力倾向，可能解释了扩大的基因组。乳品环境的代谢适应性很明显，尤其是乳糖摄取对应于嗜热链球菌。基因组衰减不如嗜热链球菌（10.-19％）先进，可能是由于乳品发酵的历史较短。

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