This work describes a new procedure that allows the targeted modification of the human gut microbiota by using antibodies raised against bacterial surface-associated proteins specific to the microorganism of interest.

To this end, a polyclonal antibody recognising the surface-associated protein Surface Layer Protein A of Lactobacillus acidophilus DSM20079T was developed.

By conjugating this antibody with fluorescent probes and magnetic particles, we were able to specifically identify this bacterium both in a synthetic, and in real gut microbiota by means of a flow cytometry approach. Further, we demonstrated the applicability of this antibody to deplete complex human gut microbiota from L. acidophilus in a single step. L. acidophilus was found to interact with other bacteria both in synthetic and in real microbiota, as reflected by its concomitant depletion together with other species.

Further optimization of the procedure including a trypsin step enabled to achieve the selective and complete isolation of this species. Depleting a single species from a gut microbiota, using antibodies recognizing specific cell surface elements of the target organism, will open up novel ways to tackle research on the specific immunomodulatory and metabolic contributions of a bacterium of interest in the context of a complex human gut microbiota, including the investigation into therapeutic applications by adding/depleting a key bacterium.

This represents the first work in which an antibody/flow-cytometry based application enabled the targeted edition of human gut microbiota, and represents the basis for the design of precision microbiome-based therapies.

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