PcrZ (photosynthesis control RNA Z) identified in R. sphaeroides, is a trans-acting sRNA which counteracts the redox-dependent induction of photosynthesis genes, mediated by protein regulators. Metabolism R. sphaeroides encodes several terminal oxidases which allow electron transfer to oxygen and other electron acceptors (e.g. DMSO or TMAO). Therefore, this microorganism can respire under oxic, micro-oxic and anoxic conditions under both light and dark conditions. Moreover, it is capable to accept a variety of carbon substrates, including C1 to C4 molecules, sugars and fatty acids. Several pathways for glucose catabolism are present in its genome, such as the Embden–Meyerhof–Parnas pathway (EMP), the Entner–Doudoroff pathway (ED) and the Pentose phosphate pathway (PP). The ED pathway is the predominant glycolytic pathway in this microorganism, whereas the EMP pathway contributing only to a smaller extent. Variation in nutrient availability has important effects on the physiology of this bacterium. For example, decrease in oxygen tensions activates the synthesis of photosynthetic machinery (including photosystems, antenna complexes and pigments). Moreover, depletion of nitrogen in the medium triggers intracellular accumulation of polyhydroxybutyrate, a reserve polymer. Biotechnological applications A genome-scale metabolic model exists for this microorganism, which can be used for predicting the effect of gene manipulations on its metabolic fluxes. For facilitating genome editing in this species, a CRISPR/Cas9 genome editing tool was developed and expanded. Moreover, partitioning of intracellular fluxes has been studied in detail, also with the help of 13C-glucose isotopomers. Altogether, these tools can be employed for improving R. sphaeroides as cell factory for industrial biotechnology. Knowledge of the physiology of R. sphaeroides allowed the development of biotechnological processes for the production of some endogenous compounds. These are hydrogen, polyhydroxybutyrate and isoprenoids (e.g. coenzyme Q10 and carotenoids). Moreover, this microorganism is used also for wastewater treatment. Hydrogen evolution occurs via the activity of the enzyme nitrogenase, whereas isoprenoids are synthesized naturally via the endogenous MEP pathway. The native pathway has been optimized via genetic engineering for improving coenzyme Q10 synthesis. Alternatively, improvement of isoprenoid synthesis was obtained via the introduction of a heterologous mevalonate pathway. Synonyms Rhodococcus minor Molisch 1907 Rhodococcus capsulatus Molisch 1907 Rhodosphaera capsulata (Molisch) Buchanan 1918 Rhodosphaera minor (Molisch) Bergey et al. 1923 Rhodorrhagus minor (Molisch) Bergey et al. 1925 Rhodorrhagus capsulatus (Molisch) Bergey et al. 1925 Rhodorrhagus capsulatus Bergey et al. 1939 Rhodopseudomonas sphaeroides van Niel 1944 Rhodopseudomonas spheroides van Niel 1944 Rhodorrhagus spheroides (van Niel) Brisou 1955 Reclassification In 2020 it