Physiology and cytological chemistry blue-green algae.

The effects of nitrogen limitation and recovery on nitrogen-containing macromolecules were followed in the cyanobacterium Aphanocapsa 6308. Removal of nitrogen from growth media triggers the degradation of the endogenous nitrogen reserves phycocyanin and cyanophycin granule polypeptide in the cyanobacterium Aphanocapsa 6308. Nitrogen recovery involves immediate synthesis of cyanophycin granule polypeptide with peak levels of 5–12% of cell dry weight found 8–12 h after a utilizable nitrogen source is added. A rapid decrease in cyanophycin granule polypeptide level then occurs and the level remains low even in light-limited stationary growth with all nitrogen sources tested except nitrate and ammonia. Protein and phycocyanin recoveries began 3 h after a utilizable nitrogen source was added. Data suggest continuous activity of the enzyme system synthesizing cyanophycin granule polypeptide in nitrogen-limited cells, but synthesis of a degrading system only after nitrogen recovery begins.

Nitrogen limitation and recovery in the cyanobacterium Aphanocapsa 6308

The occurrence of alanine dehydrogenase (AlaDH), glutamate dehydrogenase (GDH), and 2-ketoglutarate: glutamine amidotransferase (GGAT), has been surveyed in a number of blue-green algae. Among nine unicellular strains grown with nitrate, and belonging to five of the major typological groups, AlaDH was present in seven, and GDH in all eight that were assayed. In ten filamentous strains grown with nitrate, and belonging to the three nonheterocyst-forming and four heterocyst-forming groups, AlaDH was present in six, but both AlaDH and GDH were present in only one strain. In those strains which could be grown with N2 as sole nitrogen source, levels of GDH were generally lower, and AlaDH higher in cells fixing N2 than in those growing with nitrate. GGAT was undetectable in N2-grown cells. Two unicellular and three filamentous strains were tested for their ability to use L-alanine, L-glutamate, L-glutamine, and L-asparagine as sole sources of nitrogen. Of these, L-asparagine was utilized most effectively. There was little difference in levels of GDH in cells grown with nitrate or with L-asparagine, while the levels of AlaDH were slightly lower in cells grown with L-asparagine.

Ammonia assimilation in blue-green algae.

Transport of basic amino acids by the dinitrogen-fixing cyanobacterium Anabaena PCC 7120.

The growth response of the marine blue-green alga, Agmenellum quadruplicatum to 60 inorganic and organic nitrogen sources was studied. These compounds were offered as sole nitrogen sources. Most amino acids, most purines, and urea were good nitrogen sources for growth.

A survey of available nitrogen sources for growth of the blue-green alga, Agmenellum quadruplicatum.

virus-like reproduct ion has repeatedly been pos tu la ted for Rickettsiaeeae bu t so far could never be definitely p roved [2, 3]. t~ickettsiella chironomi has to be considered as a new type of microorganism, morphological ly well defined [4], whose in t racellular paras i t ism leads to a typical, reproducible disease in insects [5~, and whose reproduct ive cycle can be character ized by the occurrence of \"mul t ip le cell divis ion\".

G. G. Lawley

Papers

Blue-green algal responses to some organic-nitrogen substrates