Oligotroph A microorganism specifically adapted to grow under conditions of low nutrient supply

Oligotrophic Term used to describe lakes or oceans that lack carbon and energy sources for photosynthetic organisms

Organic Of or relating to any covalently bonded compound containing carbon atoms; derived from living systems; more recently, given the fact that all known living systems contain carbon in reduced form (i.e., not carbonate), “organic” has come to mean “containing reduced carbon”

Oxaloacetate A salt or ester of oxaloacetic acid

Oxidation/reduction The change in the oxidation state of atoms or ions due to the “loss” or “gain” of electrons

Panspermia The theory that microorganisms or biochemical compounds from outer space are responsible for originating life on Earth and possibly in other parts of the universe where suitable atmospheric conditions exist

PCR Polymerase chain reaction

Peptide Any of various natural or synthetic compounds containing two or more amino acids linked by the carboxyl group of one amino acid and the amino group of another

Peptidoglycan A polymer found in the cell walls of prokaryotes that consists of polysaccharide and peptide chains in a strong molecular network

Peridotite Any of a group of igneous rocks composed mainly of olivine and various pyroxenes and having a granitelike texture

Phosphide A compound of phosphorus and a more electropositive element or radical

Phosphorylation Chemical process in which a phosphate group is added to an organic molecule

Photolysis The decomposition of a substance into simpler units as a result of the action of light

Phylogenetic Relating to evolutionary history

Piezophile An organism adapted to living in high-pressure environments, such as hydrothermal vents

Pigment A colored molecule

Polycyclic aromatic hydrocarbons (PAHs) A class of very stable organic molecules that are made up of only carbon and hydrogen; are flat, with each carbon having three neighboring atoms, much like graphite; and are a standard product of combustion

Polyelectrolyte An electrolyte, such as a protein or polysaccharide, that has a high molecular weight

Polysaccharides A class of high-molecular-weight carbohydrates that can be broken down to monosaccharides on hydrolysis

Prebiotic Occurring before life appeared on Earth

Protein Any of a group of complex organic compounds, consisting essentially of com-

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