Inorganic nitrogen regulation of glutamate uptake in the cyanobacterium Nostoc muscorum

Abstract

1991. Inorganic nitrogen regulation of glutamate uptake in the cyanobacterium Nosioc muscorum. -Physiol. Piant. 82: 257-260.In Nosioc muscorum (Anabaena ATCC 27893) glutamate was not metabolised as a fixed nitrogen source, rather it functioned as an inhibitor of growth. The latter effect was nitrogen source specific and occurred in Ni-fixing cultures but not in cultures assimilating nitrate or ammonium. NOj-grown cultures lacked heterocysts and tiitrogenase activity and showed a nearly 50% reduction in glutamate uptake rates, as well as in the final extent of glutamate taken up, compared to N,-fixing or nitrogen-limited control cultures. NH4-grown cultures showed a similar response, except that the reduction in glutamate uptake rates and the final extent of glutamate taken up was over 80%. The present results suggest a relation between nitrate/ammonium nitrogen-dependent inhibition of glutamate uptake, probably via repression of the glutamate transport system, and glutamate toxicity.

Effect of a constant supply of different nitrogen sources on protein and carbohydrate content and enzyme activities of Anabaena variabilis cells

“…Nitrogen fixation in continuous cultures with 1.1 or 2.2 mM NH4 has been reported in bacteria (Fritzsche and Niemann 1990). By contrast, nitrogenase activity is absent in batch cultures with 1 tnM NHJ of A variabilis and Nostoc muscorum (Ernst et al 1990, Prakasham et al 1991. Either NHJ per se , Sing et al 1983, Mackerras and Smith 1986 or glutamine or another metabolite derived from NHJ assimilation (Ohmori and Hattori 1972, Stewart and Rowell 1975, Haselkom 1987, Helber et al 1988) have been proposed as the primary regulatory signal for nitrogenase repression.…”

“…It has been reported that NH 4 per se cyanobacterial species studied. For instance in Ana- (Singh et al 1983) or a product from its assimilation, baena ATCC 27893 (formerly Nostoc muscorum) and such as glutamine or a derivative (Ohmori and Hattori Anabaena cylindrica (CCAP 1403/2a) NO3 represses the 1972, Stewart and Rowell 1975), drastically inhibit the formation of heterocysts and thereby fixation of N, nitrogenase activity either by repression or inactivation (Meeks et al 1983, Renstrom-Kellner et al, 1990, of ttie enzyme, Cyanobacterial nitrogenase activity has Prakasham et al, 1991), However, in Anabaena sp. strain CA (ATCC 33047) NO3 promotes nitrate reductase synthesis and represses nitrogenase formation (Ramos and Guerrero 1983).…”

A Common Transport System for Methionine, l-methionine-dl-Sulfoximine (MSX), and Phosphinothricin (PPT) in the Diazotrophic Cyanobacterium Nostoc muscorum

“…The Nostoc muscorum strain used in the present study is a fresh water isolate and has been reported extensively in various research publications [17,22,23]. Axenic batch cultures of parent N. muscorum and its L-methionine-DLsulfoximine resistant (MSX-R) and phosphinothricinresistant (PPT-R) mutant strains were routinely grown and maintained in combined nitrogen-free medium (BG 11 0 ) under a photon fluence rate of 50 lmole m -2 S -1 and at a temperature of 28 ± 2°C [20].…”

“…Additionally, they utilize amino acids as nitrogen sources with different growthpromoting activities [8,26,27]. Glutamate, a growthinhibitory amino acid in Anabaena variabilis [6], and Nostoc muscorum [17] behave differently in Anabaena cylindrica [19]. On the other hand, inorganic nitrogen compounds protect cyanobacteria from toxic amino acids [23].…”