Endoskeleton three phyla and one subclass of animals, endoskeletons of various complexity are found: Chordata, Echinodermata, Porifera, and Coleoidea. An endoskeleton may function purely for support (as in the case of sponges), but often serves as an attachment site for muscle and a mechanism for transmitting muscular forces. A true endoskeleton is derived from mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The poriferan 'skeleton' consists of microscopic calcareous or siliceous spicules or a spongin network. The Coleoidae do not have a true endoskeleton in the evolutionary sense; there, a mollusk exoskeleton evolved into several sorts of internal
Bacterial phyla Gram positive bacteria, many of which are notable secondary metabolite producers. There are only two phyla of monoderm Gram positive bacteria, the other being the "Firmicutes"; the actinobacteria generally have higher GC content so are sometimes called "high-CG Gram positive bacteria". Notable genera/species include "Streptomyces" (antibiotic production), "Propionibacterium acnes" (odorous skin commensal) and "Propionibacterium freudenreichii" (holes in Emmental) The "Aquificae" (diderm Gram negative) contains only 14 genera (including Aquifex and Hydrogenobacter). The species are hyperthermophiles and chemolithotrophs (sulphur). According to some studies, this may be one of the most deep branching phyla. The "Bacteroidetes" (diderm Gram negative) is a member