Gut microbiota drives structural variation of exogenous probiotics to enhance colonization.

Probiotics encounter colonization resistance from native gut microbiomes, affecting their effectiveness. Genetic engineering of probiotics lacks universal applicability, as gut microbiotas are highly individualized. Here, we employed probiotic HNU082 (Lp082) to test whether Lp082 gut-adapted mutants can resolve colonization resistance in a new gut environment. Relying on culture-based methods and metagenomics, two distinct evolutionary clades of Lp082 in mice gut were observed, where one clade, which acquired more mutations, exhibited a longer survival time. However, these Lp082 isolates carrying many single nucleotide variants (SNVs) still exhibited phenotypic inconsistencies, with 13 strains of enhanced acid resistance. Thus, nanopore sequencing was proposed to identify structural variations (SVs). Among them, 12 strains had the Cro/C1-type HTH DNA-binding domain insertion, which enhanced growth and reproduction under bile salt stress, thereby increasing colonization time and quantity in the gut. The gut domestication process can drive probiotics to undergo many SNVs and SVs, thereby enhancing their colonization ability, which provides new insights into the colonization mechanisms and offers an ecology-based strategy.