This comprehensive literature review of the phosphorus nutrition and metabolism of eukaryotic microalgae deals sequentially with (1) extracellular P-compounds available for algal utilization and growth; (2) orthophosphate uptake mechanisms, kinetics, and influence from environmental variables; (3) phosphatase-mediated utilization of organic phosphates involving multiple enzymes, induction and cellular location of repressible and irrepressible phosphatases, and their role in growth physiological processes; (4) intracellular phosphate metabolism covering diversity of phosphometabolites. ATP-linked energy regulation, polyphosphate pools and storage roles, phospholipids and phospholipases; (5) steady-state and transient-state models relating phosphate utilization to growth; (6) ecological aspects covering manifestations of phosphorus limitation, interspecific competition for phosphonutrients among microorganisms, and current views on phosphorus cycling and turnover in aquatic ecosystems. Although concentrating on the microalgae, the review often points out sounder conclusions drawn from bacteria and fungi, and includes specific macroalgae in considering certain subtopics where such algae were better investigated and provided a good basis for comparison with the microalgae.

The utilization of inorganic and organic phosphorous compounds as nutrients by eukaryotic microalgae: a multidisciplinary perspective: part 1

Long-chain alkenes and alkenones in the marine coccolithophorid Emiliania huxleyi

Carotenoids with cyclic end groups are essential components of the photosynthetic membranes in all plants, algae, and cyanobacteria These lipid-soluble compounds protect against photooxidation, harvest light for photosynthesis, and dissipate excess light energy absorbed by the antenna pigments The cyclization of lycopene (psi, psi-carotene) is a key branch point in the pathway of carotenoid biosynthesis Two types of cyclic end groups are found in higher plant carotenoids: the beta and epsilon rings Carotenoids with two beta rings are ubiquitous, and those with one beta and one epsilon ring are common; however, carotenoids with two epsilon rings are rare We have identified and sequenced cDNAs that encode the enzymes catalyzing the formation of these two rings in Arabidopsis These beta and epsilon cyclases are encoded by related, single-copy genes, and both enzymes use the linear, symmetrical lycopene as a substrate However, the epsilon cyclase adds only one ring, forming the monocyclic delta-carotene (epsilon, psi-carotene), whereas the beta cyclase introduces a ring at both ends of lycopene to form the bicyclic beta-carotene (beta, beta-carotene) When combined, the beta and epsilon cyclases convert lycopene to alpha-carotene (beta, epsilon-carotene), a carotenoid with one beta and one epsilon ring The inability of the epsilon cyclase to catalyze the introduction of a second epsilon ring reveals the mechanism by which production and proportions of beta,beta- and beta, epsilon-carotenoids may be controlled and adjusted in plants and algae, while avoiding the formation of the inappropriate epsilon,epsilon-carotenoids

Functional analysis of the beta and epsilon lycopene cyclase enzymes of Arabidopsis reveals a mechanism for control of cyclic carotenoid formation.

Algal chemodiversity and bioactivity: sources of natural variability and implications for commercial application.

http://www.jbc.org/content/248/20/7215.full.pdf

Isolation and Properties of the Envelope of Spinach Chloroplasts

Publisher Summary This chapter discusses the quantitative determination of carotenoids in photosynthetic tissues. A useful separation of carotenoid pigments into nonpolar carotenes and carotenoid esters in one group, and polar xanthophylls (containing hydroxyl groups) in the other may be accomplished by partitioning the pigments between petroleum ether and aqueous methanol. This can be done by dissolving the extract in aqueous methanol in a separatory funnel and adding an equal amount of petroleum ether. In cases where the carotenoid components are stable toward alkali, it is advantageous to include saponification in the isolation procedure for removing chlorophyll and other saponifiable matter. The pigment is taken to dryness (oil pump); all acetone must be removed from the extract to avoid base-catalyzed formation of condensation products of acetone. The residue is dissolved in a small volume of ether, and the same volume of 10% methanolic KOH solution is added. The approximate content of total carotenoids in an extract may be determined by measuring the optical density of a sample suitably diluted.

Arne Jensen

Papers

[56] Quantitative determination of carotenoids in photosynthetic tissues

Recent progress in carotenoid chemistry

Algal carotenoids and chemotaxonomy

Chloroplast pigments and algal systematics