Studies on Nitrogen-Fixing Blue-Green Algae. I. Growth and Nitrogen Fixation by Anabaena Cylindrica Lemm

LITTLE ATTENTION has been given to the more general features of the physiology of the blue-green algae. Specific attention has been given to nitrogen fixation (e.g., Allison et al., 1937; Burris and Wilson, 1946; Fogg, 1947) and limited aspects of photosynthesis (e.g., Emerson and Lewis, 1942; Frenkel et al., 1950; Duysens, 1952; Brown and Webster, 1953). Nutritional requirements have been investigated, notably by Fogg (1949), Gerloff et al. (1950, 1952) and Allen (1952). However, no study has been carried to the point of developing a blue-green alga as a reliable tool organism for physiological studies. There have been two obstacles to such development. One may be attributed to the difficulties of isolation and the lack of species in pure culture which suspend readily and submit to simplicity of manipulation possible with green algae such as Chlorella and Scenedesmus. A second difficulty arises from inadequate provision of carbon dioxide inherent in most of the culture methods used. Nutritional requirements have been defined in terms of the maximum growth yield obtained in cultures in cotton-stoppered flasks. Methods have not been developed for routine study of growth rate, a characteristic far more useful and interpretable for physiological work. The' present paper presents a development of culture media and methods which has led to description of the salient growth characteristics of three blue-green algae: Anabaena variabilis, Anacystis nidulans, and Nostoc muscorum G. Fragmentary data on three other blue-green algae are included. MATERIALS AND METHODS.-Because of the uncertainties of taxonomy of the simpler algae the species used will be described in terms of their history. 1. Anabaena variabilis (Kiitzing). Filamentous, but filaments very short in turbulent culture; isolated by and obtained from R. C. Hecker as Cylindrospermum sp. (1950); revised identification by E. G. Pringsheim. 2. Anacystis nidulans. Twoto four-cell filaments, but unicellular in turbulent culture; established as a unicellular culture by one of us (WK) and purified by M. B. Allen, tentative identification by F. Drouet; original description not found. 3. Nostoc muscorum G (Kiitzing). Filamentous, but filaments short in turbulent culture; obtained from G. C. Gerloff. 4. Nostoc muscorum A (Kiitzing). Filamentous, forming clumps even in turbulent culture; isolated by and obtained from F. E. Allison. 5. Anabaena cylindrica (Lemmerman) . Fila-

Nutrition and growth of several blue-green algae

Culture experiments with the estuarine diatom Thalassiosira pseudonana (clone 3H) in highly chelated seawater media demonstrate that growth rate inhibition and copper content of cells are related to cupric ion activity, and not to total copper concentration. Cupric ion activity was altered independently of total copper concentration by varying the chelator concentration, and the pH. Cellular copper content (moles/ cell) of 3 to 4 day old cultures followed a hyperbolic relation with cupric ion activity: 4.8 X 10• Gou Cu/cell = acu + 10 0.2 where a ou is the cupric ion activity. Copper inhibited growth rate at activities above 3 X 10-u M and growth ceased at values above 5 X 10--0 M; however, the relation between growth rate inhibition and cupric ion activity was not a simple hyperbolic function. In experiments with the estuarine green alga Nannochloris atomus (clone GSB nanno), growth rate inhibition also was related to cupric ion activity with partial growth rate inhibition occuring in the activity range 4 X 10-u to 2 X 10--0 M. Calculated estimates of cupric ion activity in seawater indicate that natural activity levels can be inhibitory to these phytoplankton depending on pH and the degree of copper complexation by natural organic ligands.

The relationship between cupric ion activity and the toxicity of copper to phytoplankton [Thalassiosira pseudonana, Nannochloris atomus, Algae]

Due to significant lipid and carbohydrate production as well as other useful properties such as high production of useful biomolecular substrates (e.g., lipids) and the ability to grow using non-potable water sources, algae are being explored as a potential high-yield feedstock for biofuels production. In both natural and engineered systems, algae can be exposed to a variety of environmental conditions that affect growth rate and cellular composition. With respect to the latter, the amount of carbon fixed in lipids and carbohydrates (e.g., starch) is highly influenced by environmental factors and nutrient availability. Understanding synergistic interactions between multiple environmental variables and nutritional factors is required to develop sustainable high productivity bioalgae systems, which are essential for commercial biofuel production. This article reviews the effects of environmental factors (i.e., temperature, light and pH) and nutrient availability (e.g., carbon, nitrogen, phosphorus, potassium, and trace metals) as well as cross-interactions on the biochemical composition of algae with a special focus on carbon fixation and partitioning of carbon from a biofuels perspective.

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James B. Walker

Papers

Inorganic micronutrient requirements of chlorella. I. Requirements for calcium (or strontium), copper, and molybdenum.

Arginosuccinic Acid from Chlorella.

An enzymatic reaction between canavanine and fumarate.

Canavanine and homoarginine as antimetabolites of arginine and lysine in yeast and algae.

The formation of arginosuccinic acid from arginine and fumarate.