Selection and characterization of a SpaCBA pilus-secreting food-grade derivative of Lacticaseibacillus rhamnosus GG

Abstract

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

Maximum depth sequencing reveals an ON/OFF replication slippage switch and apparent in vivo selection for bifidobacterial pilus expression

“…7 ) is likely explained by positive selection for the phenotype associated with production of sortase-dependent pili at the surface of the bacteria. While such pilus expression could trigger the immune system 53 , 54 and so contribute to decrease their abundance, surface-exposed appendages may also be important for retention within the gut 55 . Such an in vivo/in vitro selection for particular variants is well observed in a number of host-adapted pathogens encoding genes which undergo similar phase-variation events 56 , 57 .…”

Lactobacillus rhamnosus and Staphylococcus epidermidis in gut microbiota: in vitro antimicrobial resistance

“…Among the bacteria involved, Lactic acid bacteria (LAB), specifically Lactobacillus species, resides heavily as a beneficial microbe in the GI tract (Wang et al 2014 ). As they are recognized as safe microorganisms, these bacteria are classified as probiotics (Tytgat et al 2021 ). The Lactobacillus rhamnosus is currently detected as a dominant bacteria in the human gut (Nishiyama et al 2016 ).…”