Ammonia assimilation in Bacillus polymyxa. 15N NMR and enzymatic studies

Pathways of ammonia assimilation into glutamic acid and alanine in Bacillus polymyxa were investigated by 15N NMR spectroscopy in combination with measurements of the specific activities of glutamate dehydrogenase, glutamine synthetase, glutamate synthetase, alanine dehydrogenase, and glutamic-alanine transaminase. Ammonia was found to be assimilated into glutamic acid predominantly by NADPH-dependent glutamate dehydrogenase with a Km of 2.9 mM for NH4+ not only in ammonia-grown cells but also in nitrate-grown and nitrogen-fixing cells in which the intracellular NH4+ concentrations were 11.2, 1.04, and 1.5 mM, respectively. In ammonia-grown cells, the specific activity of alanine dehydrogenase was higher than that of glutamic-alanine transaminase, but the glutamate dehydrogenase/glutamic-alanine transaminase pathway was found to be the major pathway of 15NH4+ assimilation into [15N]alanine. The in vitro specific activities of glutamate dehydrogenase and glutamine synthetase, which represent the rates of synthesis of glutamic acid and glutamine, respectively, in the presence of enzyme-saturating concentrations of substrates and coenzymes are compared with the in vivo rates of biosynthesis of [15N]glutamic acid and [alpha,gamma-15N]glutamine observed by NMR, and implications of the results for factors limiting the rates of their biosynthesis in ammonia- and nitrate-grown cells are discussed

Glutamate biosynthesis in Bacillus azotofixans. 15N NMR and enzymatic studies

Pathways of ammonia assimilation into glutamic acid in Bacillus azotofixans, a recently characterized nitrogen-fixing species of Bacillus, were investigated through observation by NMR spectroscopy of in vivo incorporation of 15N into glutamine and glutamic acid in the absence and presence of inhibitors of ammonia-assimilating enzymes, in combination with measurements of the specific activities of glutamate dehydrogenase, glutamine synthetase, glutamate synthase, and alanine dehydrogenase. In ammonia-grown cells, both the glutamine synthetase/glutamate synthase and the glutamate dehydrogenase pathways contribute to the assimilation of ammonia into glutamic acid. In nitrate-grown and nitrogen-fixing cells, the glutamine synthetase/glutamate synthase pathway was found to be predominant. NADPH-dependent glutamate dehydrogenase activity was detectable at low levels only in ammonia-grown and glutamate-grown cells. Thus, B. azotofixans differs from Bacillus polymyxa and Bacillus macerans, but resembles other N2-fixing prokaryotes studied previously, as to the pathway of ammonia assimilation during ammonia limitation. Implications of the results for an emerging pattern of ammonia assimilation by alternative pathways among nitrogen-fixing prokaryotes are discussed, as well as the utility of 15N NMR for measuring in vivo glutamate synthase activity in the cell

Effect of the nitrogen source on glutamine and alanine biosynthesis in Neurospora crassa. An in vivo 15N nuclear magnetic resonance study

The influences of different nitrogen sources on the relative rates of biosynthesis of glutamine and alanine have been studied by 15N nuclear magnetic resonance spectroscopy of intact Neurospora crassa mycelia suspensions. The rate of glutamine synthesis was fastest after growth in media deficient in free ammonium ion, whereas it was slowest following growth in media containing both glutamic acid and glutamine. The reverse trend was observed for the biosynthesis of alanine. A competition between the two biosynthetic pathways for the same substrate, glutamic acid, was found to limit the rate of alanine synthesis when glutamine synthesis was rapid. The observed in vivo rates of these reactions are compared to the reported specific activities of the enzymes catalyzing the reactions, and implications of these results for nitrogen regulation of these pathways under various physiological conditions are discussed

A sensitivity analysis of Southwestern climate [abstract and conclusions]

EXTRACT (SEE PDF FOR FULL ABSTRACT): We provide here an estimate of the extent that modern climate in the southwest US is sensitive to changes in several parameters that reflect global climatic changes. For the purposes of this study, we define modern climate as mean monthly values for the months of February and August (called winter and summer, respectively) of temperature and precipitation, at points representing the average of cells of dimension 7.5' on a side. The area studied surrounds the drainage basin of Death Valley, California

The development of Western Australian sand plain soils for agriculture

IN a recently published economic survey of the Australian wheat growing industry, it was reported that nearly two-thirds of the farms surveyed in Western Australia were located on lateritic sand plain. As a random selection was made of the eighty farms that were visited it is reasonable to conclude that a similar proportion of all the State\u27s wheat producing farms are on that type of country. This constitutes a remarkable change from the earlier days of wheat belt settlement when the sand plain soils were regarded as virtually useless and by-passed for development. It is the purpose of this article to give a brief account of the agricultural development of those soils in the south-western part of Western Australia and to consider the factors which have been responsible for the change

Marriage by Force? Contestation over Consent and Coercion in Africa

With forced marriage, as with so many human rights issues, the sensationalized hides the mundane, and oversimplified popular discourses miss the range of experiences. In sub-Saharan Africa, the relationship between coercion and consent in marriage is a complex one that has changed over time and place, rendering impossible any single interpretation or explanation. The legal experts, anthropologists, historians, and development workers contributing to Marriage by Force? focus on the role that marriage plays in the mobilization of labor, the accumulation of wealth, and domination versus dependency. They also address the crucial slippage between marriages and other forms of gendered violence, bondage, slavery, and servile status. Only by examining variations in practices from a multitude of perspectives can we properly contextualize the problem and its consequences. And while early and forced marriages have been on the human rights agenda for decades, there is today an unprecedented level of international attention to the issue, thus making the coherent, multifaceted approach of Marriage by Force? even more necessary.https://ohioopen.library.ohio.edu/oupress/1003/thumbnail.jp

A Rasch Rating Scale Analysis of the Brief Symptom Inventory

The problem of this study addresses a preliminary Rasch rating scale analysis of the Brief Symptom Inventory in relation to reliability and validity. Also, this investigator will utilize information provided by the latent trait psychometric model

Analyses of Birthdate and Growth in Beef Heifers Categorized by Puberty and Pregnancy Status

Heifer records were retrospectively evaluated to see if Julian birthdate, cycling status prior to breeding, and body weight collected from weaning through final pregnancy diagnosis differed when heifers were categorized by 5 different approaches: 1) pubertal status prior to estrous synchronization, 2) whether or not detected in estrus at AI, 3) heifers impregnated by AI vs all other heifers, 4) final pregnancy status, and 5) a 5-way classification accounting for AI and pregnancy status (AI pregnant, heifers subjected to AI that subsequently conceived to bull, heifers not AI that were impregnated by bull, heifers subjected to AI that were not pregnant, heifers not AI and not pregnant). Collectively, results support the concept that earlier birth in the calving season and greater preweaning growth are associated with desirable reproductive response in replacement beef heifers