Nitrogen Metabolism of the Haloarchaeon Haloferax volcanii
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The Ohio State University / OhioLINK
2009
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ndltd-OhioLink-oai-etd.ohiolink.edu-osu12500084172021-08-03T05:56:49Z Nitrogen Metabolism of the Haloarchaeon Haloferax volcanii Sabag-Daigle, Anice Microbiology Archaea halophiles nitrogen metabolism microarray horizontal gene transfer histidine metabolism Cells in all domains of life have developed complex regulatory schemes to ensure nitrogen homeostasis. The mechanisms associated with nitrogen homeostasis have been examined in a wide variety of organisms and the molecular aspects of these regulatory systems present a view of an essential global regulatory program for each organism. Recognizing that a similar complex regulatory scheme was most likely present in the Archaea, we chose to investigate the response of Haloferax volcanii to variations in the amount and the quality of its nitrogen source as a model of global regulation in the Archaea. Analysis of the recently sequenced H. volcanii genome showed that this organism encodes enzymes for the core ammonia assimilation pathways found in all organisms and several enzymes for the assimilation of nitrogen from alternative substrates. Phyletic distribution studies and phylogenetic analyses indicate that many of these alternative nitrogen assimilation pathways are absent in other Archaea and that they many have been acquired by the haloarchaea through horizontal gene transfer (HGT) from bacterial genomes. To investigate the global transcriptome response of H. volcanii to changes in nitrogen availability, a genome-wide tiled array was constructed and used to characterize the RNA populations of cells undergoing balanced growth, during growth with a poor nitrogen source and under conditions of nitrogen starvation. Changes in the RNA populations indicated that genes encoding core nitrogen assimilation pathways showed differential expression. However, the regulatory proteins common to the bacterial systems, and those described for Archaea, were absent in H. volcanii. An analysis of the RNAs identified a specific regulatory protein of the AsnC family in the negative regulation of the glnA gene and showed that the general transcription factor (GTF) genes, tbp and tfb, also exhibited differential expression. These data also uncovered the regulated expression of numerous genes encoding uncharacterized proteins. A notable example was a gene encoding a serine/threonine protein kinase, prkA, which is present only in the haloarchaea. This gene exhibited high levels of RNA during nitrogen starvation, and other conditions of nutrient limitation, suggesting that this novel enzyme plays an important role in the physiological response to starvation in the haloarchaea. Expression of the histidine utilization genes, hutUGIH, was examined in vivo as a model for the regulation of nitrogen assimilation genes that were acquired by HGT. In vivo studies established that the positive transcription regulator, HutR, regulated the hut operon genes when histidine or urocanate was provided to cells. The HutR protein is a member of the bacterio-opsin activator (BOA) family of regulators and this class of regulator has not previously been associated with nitrogen regulation in any other organism. The results of this study provide a detailed view of the response of the haloarchaeon H. volcanii to nitrogen limitation and they have uncovered associations to genes of uncharacterized functions. These results have also established the specific regulatory mode of the hut genes, which have been acquired by HGT and are functionally assimilated into the metabolism of this haloarchaeon. 2009-09-16 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1250008417 http://rave.ohiolink.edu/etdc/view?acc_num=osu1250008417 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
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NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Microbiology Archaea halophiles nitrogen metabolism microarray horizontal gene transfer histidine metabolism |
| spellingShingle |
Microbiology Archaea halophiles nitrogen metabolism microarray horizontal gene transfer histidine metabolism Sabag-Daigle, Anice Nitrogen Metabolism of the Haloarchaeon Haloferax volcanii |
| author |
Sabag-Daigle, Anice |
| author_facet |
Sabag-Daigle, Anice |
| author_sort |
Sabag-Daigle, Anice |
| title |
Nitrogen Metabolism of the Haloarchaeon Haloferax volcanii |
| title_short |
Nitrogen Metabolism of the Haloarchaeon Haloferax volcanii |
| title_full |
Nitrogen Metabolism of the Haloarchaeon Haloferax volcanii |
| title_fullStr |
Nitrogen Metabolism of the Haloarchaeon Haloferax volcanii |
| title_full_unstemmed |
Nitrogen Metabolism of the Haloarchaeon Haloferax volcanii |
| title_sort |
nitrogen metabolism of the haloarchaeon haloferax volcanii |
| publisher |
The Ohio State University / OhioLINK |
| publishDate |
2009 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=osu1250008417 |
| work_keys_str_mv |
AT sabagdaigleanice nitrogenmetabolismofthehaloarchaeonhaloferaxvolcanii |
| _version_ |
1719428257685700608 |