Many studies have established the functional properties of Lacticaseibacillus rhamnosus GG, previously known as Lactobacillus rhamnosus GG, marketed worldwide as a probiotic. The extraordinary capacity of L. rhamnosus GG to bind to human mucus and influence the immune system especially stand out. Earlier, we have shown the key role of its SpaCBA sortase-dependent pili encoded by the spaCBA-srtC1 gene cluster herein. These heterotrimeric pili consist of a shaft pilin SpaA, a basal pilin SpaB, and tip pilin SpaC that contains a mucus-binding domain. Here, we set out to characterize a food-grade non-GMO mutant of L. rhamnosus GG, strain PA11, which secretes its pilins, rather than coupling them to the cell surface, due to a defect in the housekeeping sortase A. The sortase-negative strain PA11 was extensively characterized using functional genomics and biochemical approaches and found to secrete the SpaCBA pili into the supernatant. Given the functional importance and uniqueness of the mucus-binding pili of L. rhamnosus GG, strain PA11 offers novel opportunities towards the characterization and further therapeutic application of SpaCBA pili and their low-cost, large-scale production.

Key points

•Creation of pilus-secreting mutant (PA11) of the key probiotic LGG.

•Strain PA11 is defective in a functional housekeeping sortase SrtA.

•Strain PA11 opens novel biotherapeutic application avenues.

Graphical abstract

中文翻译：

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鼠李糖乳杆菌GG分泌SpaCBA菌毛的食品级衍生物的选择和表征

许多研究已经确定了鼠李糖乳杆菌GG（以前称为鼠李糖乳杆菌GG）的功能特性，该菌作为益生菌在世界范围内销售。鼠李糖乳杆菌GG结合人粘液并影响免疫系统的非凡能力尤其突出。此前，我们已经显示了由spaCBA-srtC1基因簇编码的其SpaCBA分选酶依赖性菌毛的关键作用。这些异三聚体菌毛由杆状菌毛SpaA，基底菌毛SpaB和含有黏液结合结构域的尖端菌毛SpaC组成。在这里，我们着手表征鼠李糖乳杆菌的食品级非转基因突变体GG，PA11菌株，由于管家分选酶A的缺陷而分泌其菌毛，而不是将其偶联到细胞表面。分选阴性的PA11菌株使用功能基因组学和生化方法进行了广泛表征，并发现其分泌SpaCBA将菌毛倒入上清液中。鉴于鼠李糖乳杆菌GG黏液结合菌毛的功能重要性和独特性，PA11菌株为SpaCBA菌毛的表征和进一步治疗应用及其低成本，大规模生产提供了新的机会。

关键点

•创建关键益生菌LGG的菌毛分泌突变体（PA11）。

•菌株PA11在功能性客房整理分拣酶SrtA中有缺陷。

•菌株PA11开辟了新颖的生物治疗应用途径。

图形概要