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Genetics and physiology of osmoregulation in Escherichia coli: mechanisms of osmotic regulation of trancription of the proU Operon

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Title Genetics and physiology of osmoregulation in Escherichia coli: mechanisms of osmotic regulation of trancription of the proU Operon
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Contributor Gowrishankar, J
 
Subject Molecular Biology
Cellular Biology
prou Operon
Genetics
Escheria coli
osmoregulation
transcription
 
Description The ability of organisms to adapt to fluctuations in growth conditions is of fundamental importance
newlinefor their survival. One of the factors that directly affects growth of plants and bacteria is the osmolarity of
newlineextracellular environment, and these organisms exhibit remarkable similarity in their response to hyperosmotic
newlinestress conditions. Unicellular bacteria like Escherichia coli and Salmonella typhimurium are able
newlineto survive and grow in a wide range of osmolarities by carrying out a set of active processes, and this
newlinephenomenon of adaptation is known as osmoregulation. In these organisms, long-term adaptation to
newlinehyper-osmotic stress involves the accumulation of certain solutes, called compatible solutes, such as
newlinetrehalose, glutamate, proline and glycine betaine. Compatible solutes are so called because they exhibit
newlineminimal inhibitory effect on cellular metabolism, even when accumulated to concentrations of several
newlinehundreds of milimolar in the cytoplasm; amongst the compatible solutes, glycine betaine has been shown
newlineto be the most potent in alleviating the inhibitory effects of osmotic stress.
newlineThe proU locus in E coli and S. typhimurium encodes an osmotically inducible transport system
newlinefor active uptake of glycine betaine and of proline, and thus plays an important role in osmoregulation in
newlinethese organisms~ Molecular and genetic analysis has shown that proU is an operon consisting of three
newlinegenes that encodes a binding-protein-dependent transport system. Studies on cis-regulation of the proU
newlineoperon in E coli have shown the presence of two promoters P1 and P2, along with a negative regulatory
newlineelement (NRE) present downstream of P2 and extending into the first structural gene proV. Promoter-lac
newlinefusion studies indicated that expression from each of the two promoter P1 and P2 is separately osmotically
newlineinducible, by about five- and eight-fold respectively, whereas deletion of the NRE results in derepression
newlineof proU expression at low osmolarity.
References p.92-113
 
Date 2013-12-26T09:12:38Z
2013-12-26T09:12:38Z
2013-12-26
n.d.
1994
n.d.
 
Type Ph.D.
 
Identifier http://hdl.handle.net/10603/14267
 
Language English
 
Relation -
 
Rights university
 
Format iv, 92p.
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None
 
Coverage Biology
 
Publisher Delhi
Jawaharlal Nehru University
Centre for Molecular and Cellular Biology
 
Source INFLIBNET