Neuraminidase A-Exposed Galactose Promotes Streptococcus pneumoniae Biofilm Formation during Colonization
Neuraminidase A-Exposed Galactose Promotes Streptococcus pneumoniae Biofilm Formation during Colonization
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DOI：
10.1128/iai.00277-16
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发表时间：
2016-10-01
影响因子：
3.1
通讯作者：
Orihuela, Carlos J.
中科院分区：
文献类型：
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作者：
Blanchette, Krystle A.;Shenoy, Anukul T.;Orihuela, Carlos J.
肺炎链球菌是一种定植于鼻咽部的机会致病菌。在这里，我们表明，碳的可用性是不同的鼻咽和成人的血流：葡萄糖是从鼻咽缺席，而半乳糖是丰富的。我们证明，肺炎球菌神经氨酸酶A（NanA），它从宿主糖蛋白中切割末端唾液酸残基，暴露在隔膜上皮细胞表面的半乳糖，从而增加其在定植过程中的可用性。我们观察到S. NanA和β-半乳糖苷酶A（BgaA）缺陷的肺炎链球菌突变体不能在体内形成生物膜，尽管在体外具有正常的生物膜形成能力。随后，我们观察到，葡萄糖，蔗糖，果糖是抑制生物膜的形成，而半乳糖，乳糖，和低浓度的唾液酸是允许的。这些发现共同表明，参与生物膜形成的基因处于某种形式的碳分解代谢物抑制（CCR）之下，这是一种调节网络，其中参与不太偏好的糖的吸收和代谢的基因在与偏好的糖一起生长期间被沉默。支持这一观点，我们观察到丙酮酸氧化酶缺陷的突变体，其在非CCR诱导生长条件下将丙酮酸转化为乙酰磷酸，不能形成生物膜。随后的比较转录组测序（RNA-seq）分析的嗜酸性和生物膜生长的肺炎球菌表明，涉及丙酮酸转化为乙酰磷酸和随后导致脂肪酸生物合成的代谢途径在不同的生物膜生长条件下一致上调。我们的结论是碳在鼻咽部的可用性影响体内肺炎球菌生物膜的形成。此外，生物膜形成涉及以前未被认识到发挥重要作用的代谢途径。
Streptococcus pneumoniae is an opportunistic pathogen that colonizes the nasopharynx. Herein we show that carbon availability is distinct between the nasopharynx and bloodstream of adult humans: glucose is absent from the nasopharynx, whereas galactose is abundant. We demonstrate that pneumococcal neuraminidase A (NanA), which cleaves terminal sialic acid residues from host glycoproteins, exposed galactose on the surface of septal epithelial cells, thereby increasing its availability during colonization. We observed that S. pneumoniae mutants deficient in NanA and beta-galactosidase A (BgaA) failed to form biofilms in vivo despite normal biofilm-forming abilities in vitro. Subsequently, we observed that glucose, sucrose, and fructose were inhibitory for biofilm formation, whereas galactose, lactose, and low concentrations of sialic acid were permissive. Together these findings suggested that the genes involved in biofilm formation were under some form of carbon catabolite repression (CCR), a regulatory network in which genes involved in the uptake and metabolism of less-preferred sugars are silenced during growth with preferred sugars. Supporting this notion, we observed that a mutant deficient in pyruvate oxidase, which converts pyruvate to acetyl-phosphate under non-CCR-inducing growth conditions, was unable to form biofilms. Subsequent comparative transcriptome sequencing (RNA-seq) analyses of planktonic and biofilm-grown pneumococci showed that metabolic pathways involving the conversion of pyruvate to acetyl-phosphate and subsequently leading to fatty acid biosynthesis were consistently upregulated during diverse biofilm growth conditions. We conclude that carbon availability in the nasopharynx impacts pneumococcal biofilm formation in vivo. Additionally, biofilm formation involves metabolic pathways not previously appreciated to play an important role.