Plakortis: A genus of SPONGES in the family Plakinidae, with the skeleton formed by small diactine (and some triactine) needle-like terminations.Planococcus Bacteria: A genus of coccoid bacteria in the family PLANOCOCCACEAE. They are widely distributed in various habitats including sea water, freshwater ponds, cyanobacterial mats, and in marine animals.Polyketides: Natural compounds containing alternating carbonyl and methylene groups (beta-polyketones), bioenergenetically derived from repeated condensation of acetyl coenzyme A via malonyl coenzyme A, in a process similar to fatty acid synthesis.Porifera: The phylum of sponges which are sessile, suspension-feeding, multicellular animals that utilize flagellated cells called choanocytes to circulate water. Most are hermaphroditic. They are probably an early evolutionary side branch that gave rise to no other group of animals. Except for about 150 freshwater species, sponges are marine animals. They are a source of ALKALOIDS; STEROLS; and other complex molecules useful in medicine and biological research.