1,720,972 research outputs found
Molecular characterization of a recombinant replication protein (Rep) from the Antarctic bacterium Psychrobacter sp. TA144.
No full textA rolling-circle plasmid from Psychrobacter sp. TA144: evidence for a novel rep subfamily.
No full textA rolling-circle plasmid from Psychrobacter sp. TA144: evidence for a novel rep subfamily.
No full textA rolling-circle plasmid from Psychrobacter sp. TA144: evidence for a novel rep subfamily.
No full textADAPTIVE RESPONSE OF ESCHERICHIA COLI TO ALKYLATING AGENTS: MOLECULAR ASPECTS AND BIOTECHNOLOGICAL APPLICATIONS IN THE BIOREMEDIATION FIELD
No full textThe increasingly stringent environmental regulations on hazardous wastes has encouraged the search for innovative solutions for the remediation of contaminated wastes. In this field, bioremediation is seen as an attractive solution due to its reputation as a low cost, environmentally friendly and publicly acceptable treatment technology. The aim of this research project was to explore new potential candidates for the bio-treatment of wastes and environments contaminated by alkylating agents. The study has been specifically focused on AidB, an enigmatic component of the response to alkylation stress in bacterium Escherichia coli. First, AidB protein was functionally characterized: it was showed to bind with high affinity DNA regions containing an upstream element and to have transcriptional activity. At this regard, it was intriguing to speculate that AidB might stimulate the transcription of genes whose products are responsible for alkylation resistance. Successively, given that the knowledge of the domain architecture is necessary for understanding the multifunctional properties of a protein, structural and functional characterization of domains present in AidB was performed. Specifically, its N-terminal region was shown to be exhibit acyl-CoA dehydrogenase activity while the short C-terminal domain was shown to be responsible for the DNA binding activity and for regulatory function. The study was then aimed at investigate the mechanism by which AidB directly protects E. coli cells against alkylating compounds. It was demonstrated that this protein prevents alkylation damage and it does so by protecting DNA and, presumably, by inactivating alkylators before they are able to react with their target. Interestingly, a recent report on the three dimensional structure of AidB bound to double strand DNA supported this model, revealing that the protein is well equipped to sterically occlude DNA from attack by damaging agents. Importantly, the unique chemical environment of FAD active site provided a rationale for a possible role of AidB in deactivation of nitrosoguanidines such as N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) and N-ethyl-N′-nitro-N-nitrosoguanidine (ENNG). Coupled with structural analysis, the results obtained in this work supported the hypothesis that AidB might act as a detoxification enzyme to destroy nitrosoguanidines: indeed, it was demonstrated that aidB mutant cells display decreased resistance to MNNG and ENNG and no change in sensitivity to other classes of alkylators; besides, AidB was showed to allow more efficient gene transcription in E. coli cells exposed to nitrosoguanidines rather than to other mutagens. Therefore, AidB represents a promising tool for the bio-treatment of sites contaminated by certain alkylating agents. On the basis of data described above, this experimental work was ultimately targeted at identify as well as at characterize E. coli AidB homologues in bacteria used for bioremediation applications. Specifically, the acyl-CoA dehydrogenase coded by the PP4780 gene from Pseudomonas putida KT2440 was the object of this investigation. The PP4780 gene was expressed in aidB and wild type E. coli strains and its involvement in the protection against alkylating agents was tested. Interestingly, the complementation of the aidB mutation by PP4780 restored the resistance phenotype to lethal and mutagenic effects of MNNG and ENNG; besides, recombinant cells that overexpress PP4780 were shown to possess increased resistance to nitrosoguanidines as compared with wild type and aidB-overexpressing cells. On the basis of these observations, the acyl-CoA dehydrogenase from P. putida has been demonstrated to be involved in the response to alkylation stress, presumably functioning as a detoxification enzyme. In conclusion, the data obtained strongly support the possibility of developing new successful strategies for the bioremediation of sites contaminated by alkylating compounds
Secretion of alpha-amylase from Pseudoalteromonas haloplanktis TAB23: two different pathways in different hosts
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The thiol-disulfide oxidoreductase system in the cold-adapted bacterium Pseudoalteromonas haloplanktis TAC125: discovery of a novel disulfide oxidoreductase enzyme
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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