Abstract: This invention discloses novel bacterial spore systems. Genetically modified or genetically engineered viable spore systems expressing bioactive polypeptides, for example bacteriocins and/or enzymatically active feed enzymes, at the spore surface, have a great potential use in animal feeding. Genetically modified or “genetically engineered inert spore systems expressing affinity ligands or immobilized enzymes at the surface have a great potential use in biocatalysis and in the construction of biocatalytic films. Especially the resistance to harsh chemicals, desiccation, strong pressure, or high temperatures allows the spores to be a potentially valuable tool for the display of bioactive molecules, like biocatalytic enzymes or bioactive feed enzymes that must survive harsh conditions to deliver their full potential.