The peculiar carbon metabolism in diatoms.

Abstract

Diatoms are microalgae that arose over the last 100 Myr, thus phylogenetically constituting a relatively recent group of organisms. Analysis of microfossils that can be traced through geological time, as well as their contributions to seafloor sediments and fossil fuel reserves, demonstrates that diatoms have played a crucial role during this time. The review by Benoiston et al . [1] in this issue combines the current information on the evolution and biogeochemical functions of diatoms over time. Paleoecological data contain information for evaluating genetic variation through past climate changes, going back thousands of years in time [2]. In their review, Godhe & Reynardson [3] suggest the adoption of multiple strains of individual species for refining our understanding of the carbon metabolism and its variation within and between species. Diatoms are photosynthetic organisms using the energy of the Sun to build up organic molecules via CO2 fixation (primary production). For a long time, land plants have been supposed to be the main primary producers, however, recent estimations consider the contribution of algae to be as high as that of land plants [4]. The key process of the photosynthetic Calvin–Bensson–Bassham cycle is the fixation of CO2 onto ribulose-1,5-bisphosphate, mediated by the catalytic enzyme activity of RuBisCO. This reaction yields 3-phosphoglycerates, which immediately are converted to triose phosphates that are required to regenerate ribulose-1,5-bisphosphate. The contribution by Jensen et al . [5] reviews the regulation of the Calvin–Benson–Bassham cycle in diatoms, presenting a regulation process that is based on transcriptional regulation. This finding contrasts with land plants, in which the Calvin–Benson–Bassham is mostly regulated at the enzymatic level. Because a high local CO2 partial pressure in the close vicinity of the RuBisCO is vital to avoid photorespiration, …