**4.2 Polyketides**

Polyketides are the other important compounds in the screening of secondary metabolites. Polyketides are complex molecules built from simple carboxylic acids and synthesized by polyketide synthetase [29]. Polyketides has been discovered as important lead compounds with various activities, such as blocking protein tyrosine phosphatase and inhibiting ATP synthetase complex [30]. Highly cytotoxic patellazole A, thought to have a defensive role, is a polyketide peptide hybrid made by the alpha-proteobacterium Ca. *Endolissoclinum faulkneri*. This bacteria was found only in a subgroup of *Lissoclinum patella*, and its genome is extensively reduced, that the bacteria is only found in a subgroup of *Lissoclinum patella*, and its genome is reduced, such that it cannot live independently in a host. These peptides are known to maintain all the synthesized genes, providing evidence for an essential defensive role of these metabolites in this symbiotic relationship [31].
