Normal Microbiota and the Host: Microbial antagonism is competition between microbes. Normal microbiota protect the host by: occupying niches that pathogens might occupy 。producing acids producing bacteriocins Probiotics are live microbes applied to or ingested into the body,intended to exert a beneficial effect.• Microbial antagonism is competition between microbes. • Normal microbiota protect the host by: • occupying niches that pathogens might occupy • producing acids • producing bacteriocins • Probiotics are live microbes applied to or ingested into the body, intended to exert a beneficial effect. Normal Microbiota and the Host: