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ronaldinho
Nuovo Arrivato
6 Messaggi |
 Inserito il - 08 gennaio 2009 : 20:19:37
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ho trovato questo testo,ma non capisco...vorrei trovare un legame tra cyano e quel tipo di batteri...qualcuno può aiutarmi..grazie ancora
anche una risposta veloce senza tradurre tutto...
CGP was first discovered by Borzi (10) in cyanobacteria, and microbiology textbooks mention it as a polymer that exclusively occurs in cyanobacteria (37). However, recently, the occurrence of genes encoding proteins homologous to cyanobacterial cyanophycin synthetases has been described for other eubacteria not belonging to the cyanobacterial group, such as Acinetobacter sp., Bordetella bronchiseptica, Bordetella pertussis, Bordetella parapertussis, Clostridium botulinum, Desulfitobacterium hafniense, and Nitrosomonas europaea (20, 49). It was also shown that the cphA genes of Acinetobacter calcoaceticus strain ADP1 and D. hafniense encode functionally active enzymes and that cells of Acinetobacter accumulated CGP when they were cultivated under phosphate-limiting conditions, albeit at low levels (up to 1.4% [wt/wt] of the cell protein content) (20). The functionality of D. hafniense CphA was studied only in recombinant E. coli (49). When the Acinetobacter cphA gene was cloned and expressed in E. coli, a cyanophycin synthetase activity of 1.2 U per mg of protein was measured, and CGP accounted for up to 7.5% of the cell dry matter (CDM) (20). Interestingly, the CGP produced in recombinant E. coli or obtained by in vitro synthesis by using the purified enzyme of A. calcoaceticus did not contain any detectable lysine, indicating that the A. calcoaceticus cyanophycin synthetase exhibits much higher substrate specificity than other cyanophycin synthetases exhibit (21). It is also worth mentioning that downstream of cphA a gene that putatively encodes a cyanophycinase (cphI) was detected in the Acinetobacter genome (20). The genes for CphA and CphB are also clustered in many cyanobacteria, but with cphB preceding cphA. This study was aimed at evaluating the limits of cyanophycin synthesis and accumulation in A. calcoaceticus strain ADP1. |
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