Microorganisms can lend their antimicrobial activity to another organism in a symbiotic relationship. Han et al. Capitalized on reports from local fishers that a fish called the white croaker (Argyrosomus argentatus) is rarely infected by pathogens spreading through the local habitat even after feeding off of dead or infected prey. The researchers took a look at A. argentatus's gut flora, looking for a symbiot that could be the source of the fish's antimicrobial resistance. Initial extracts of the microbes isolated from the white croaker showed antibacterial activity, and in this paper they have isolated a novel alkaloid, curvulamine, which has broad-spectrum activity against gram-negative Veillonella parvula and Bacteroides vulgatus, and gram-positive Streptococcus sp. and Peptostreptococcus sp.

Read more here: http://pubs.acs.org/doi/pdf/10.1021/ol502572g