4) Fi plasmid are present in
a) Bacillus thuringiensis
c) Haemiphilous influenzae
b) Agrobacterium tumefecience
d) Escherichia coli
Answers
Answer:
I think answer is in option b
Answer:
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Explanation:
Practically all Bacillus thuringiensis strains contain a set of self-replicating, extrachromosomal DNA molecules or plasmids, which vary in number and size in the different strains. The plasmid patterns obtained from gel electrophoresis have previously been used as a tool to characterize strains, but comparison of the plasmid patterns has been limited in the number and diversity of strains analyzed. In this report, we were able to compare the plasmid patterns of 83 type strains (out of 84) and 47 additional strains from six serotypes. The information obtained from this comparison showed the importance of this tool as a strain characterization procedure and indicates the complexity and uniqueness of this feature. For example, with one exception, all type strains showed a unique plasmid pattern. All were unique in such a way that none showed even a single comigrating plasmid in the agarose gels, and therefore, cluster analysis was impossible, indicating that plasmid patterns are qualitative rather than quantitative features. Furthermore, comparison between strains belonging to the same serotype showed a great difference in variability. Some serotypes (e.g., israelensis) showed the same basic pattern among all its strains, while other serotypes (e.g., morrisoni) showed a great diversity of patterns. These results indicate that plasmid patterns are valuable tools to discriminate strains below the serotype level.
Bacillus thuringiensis is a ubiquitous bacterium (25) isolated from a great diversity of habitats, which include soil, insects, stored crop products (31), phylloplane (32), and aquatic habitats (18). Its great biotechnological success resides in the production of highly specific insecticidal proteins (Cry proteins) simultaneously with the sporulation phase. These Cry proteins are coded by genes (cry genes) harbored in megaplasmids (10, 14, 21, 34), although it has also been suggested that they are present in the chromosome (21). Plasmids have also been associated with the production of a different toxin called β-exotoxin (23). The relevance of plasmids in B. thuringiensis strains is assumed by the regular presence of a set of plasmids, which can vary in number from 1 to 17 and in size from 2 to 80 MDa (2, 9). The set of plasmids harbored in a strain are normally visualized by agarose gel electrophoresis, where they form an electrophoretic pattern of bands, according to their differential migration in the gel. Although B. thuringiensis plasmids have been studied either to locate cry genes (9, 21) or to transfer them between different strains and species (3, 5, 10, 15, 30), plasmid patterns have frequently been used to characterize strains (2, 29, 33), especially compared to those of standard strains (16, 17, 27). A plasmid pattern seems to be related to each strain, serotype, or any other subspecific group.