The discovery of penicillin is one of the first documented observations of an interaction between
bacteria and fungi mediated by small molecules. Historically molecular intergeneric interactions
were regarded mainly as growth-inhibiting interactions; however, modern research revealed that
microbial cross talk forms an integral part of our environment and covers various aspects beyond
simple antibiosis.There are instances in which natural products alter phenotypes and developmental
processes, such as sporulation or biofilm formation, and serve as virulence factors in symbiotic
and pathogenic associations involving additional partners. Specialized mutualistic relationships
have evolved in which a host organism harbors a symbiont to make use of its chemical synthesis
capabilities to combat competitors or to maintain a certain lifestyle. The growing number of
studies published in the past few years that report discoveries in this field points to an exciting
emerging area of research. Our increasing understanding of the complex networks in microbial
ecology will not only help us understand fundamental biological processes but also lead to the discovery
of new virulence factors and drug candidates. This review highlights recent contributions
to the understanding of bacteria-fungi interactions mediated by secondary metabolites that occur
in the environment and affect medicine and biotechnology.