Monograph use at an academic health sciences library: the first three years of shelf life

Objective: To study the circulation of monographs during the first three years of shelf life at an academic health sciences library.

Oxygen isotope ratios of PO4: An inorganic indicator of enzymatic activity and P metabolism and a new biomarker in the search for life

The distinctive relations between biological activity and isotopic effect recorded in biomarkers (e.g., carbon and sulfur isotope ratios) have allowed scientists to suggest that life originated on this planet nearly 3.8 billion years ago. The existence of life on other planets may be similarly identified by geochemical biomarkers, including the oxygen isotope ratio of phosphate (δ18Op) presented here. At low near-surface temperatures, the exchange of oxygen isotopes between phosphate and water requires enzymatic catalysis. Because enzymes are indicative of cellular activity, the demonstration of enzyme-catalyzed PO4–H2O exchange is indicative of the presence of life. Results of laboratory experiments are presented that clearly show that δ18OP values of inorganic phosphate can be used to detect enzymatic activity and microbial metabolism of phosphate. Applications of δ18Op as a biomarker are presented for two Earth environments relevant to the search for extraterrestrial life: a shallow groundwater reservoir and a marine hydrothermal vent system. With the development of in situ analytical techniques and future planned sample return strategies, δ18Op may provide an important biosignature of the presence of life in extraterrestrial systems such as that on Mars.

Default taxonomy: Ernst Mayr’s view of the microbial world

This perspective is a response to a taxonomic proposal by E. Mayr [“Two empires or three?” (1998) Proc. Natl. Acad. Sci. USA 95, 9720–9723]. Mayr has suggested that the now accepted classification of life into three primary domains, Archaea, Bacteria, and Eucarya—originally proposed by myself and others—be abandoned in favor of the earlier Prokaryote–Eukaryote classification. Although the matter appears a taxonomic quibble, it is not that simple. At issue here are differing views as to the nature of biological classification, which are underlain by differing views as to what biology is and will be—matters of concern to all biologists.