PAPER SHORT ABSTRACT: Examining the relational rationalities of work in breeding through inter-species human-microbe collaborations to protect against the deleterious effects of Listeria, we discuss the hygienist and commercial limits of "putting microbes to work", and thus the anthropological boundaries of work. PAPER LONG ABSTRACT: In France, the systems for producing raw milk cheeses constitute an attempt to enlist microbes in the production of taste, heritage and market values. These systems, including Protected Designations of Origin, allow breeders to protect themselves from the deleterious effects of the conventional milk market which plunge a growing number of their peers into precariousness. However, they must face the threat of proliferation of pathogens in their work, including Listeria. How do they manage this microbial ambivalence in their breeding practices? This communication shows how these actors are no longer trying to fight against, but to work with microbes, via forms of inter-species collaboration, to manage the threat-proliferation of Listeria. It is based on surveys of breeders-producers from Saint-Nectaire farmers in France as part of the TANDEM research program (INRAe HOLOFLUX Metaprogram). Firstly, we show how these actors construct “microbial balances” in their breeding practices, a microbiopolitics where their “trust” in microbes plays out in the face of Listeria “attacks”, through: exogenous recruitment – powders commercial ferments – and/or endogenous – the “environment” of the farm – of microbes deemed beneficial; more or less strict controls – disinfection, etc. - of microbial populations during milking. Secondly, we will question the broader ecological disturbances, linked to the intensification of breeding practices, which induce a degradation of this microbiopolitics: the proliferation of mole rats in the meadows.