MODERN TAXONOMY OF CYANOBACTERIA

LECT 4

What is Cloning?

The terms recombinant DNA technology, DNA cloning, molecular cloning, or gene cloning all refer to the same process: the transfer of a DNA fragment of interest from one organism to a self-replicating genetic element such as a bacterial plasmid (cloning vector). The DNA of interest can then be propagated in a foreign host cell

Plasmid for cloning

A 'plasmid' is a small, circular piece of DNA that is often found in bacteria. This innocuous molecule might help the bacteria survive in the presence of an antibiotic, for example, due to the genes it carries. To scientists, however, plasmids are important because (i) we can isolate them in large quantities, (ii) we can cut and splice them, adding whatever DNA we choose, (iii) we can put them back into bacteria, where they'll replicate along with the bacteria's own DNA, and (iv) we can isolate them again - getting billions of copies of whatever DNA we inserted into the plasmid! Plasmid are limited to sizes of 2.5-20 kilobases (kb), in general.

Blast

>gi|555|emb|X65215.1|BTMISATN B.taurus microsatellite DNA (624bp) ACCTCCACTAGCTTTGTTTGTAGTGATGCTCTGTAGCACCACTGGGAAGCCCTTTAATGAAT

GTGCCTTTCCGCAAATCA CACACACACAAATACACTTATAGAAACAAGGTGATTTTCTTGAAATAATAAAACAAAATTTGGA

AGAAGATTTTTACTGT CTTAGGAAAAGTAAGGCATTGGAAGGTGGCTAGGTATGACATATGAAGTTGCATTTTAAAAC

TGGAATTGGACAACTGAT ATTCAGTGATATTTATGCTACTACCTTCTAGAATCGAGAGCATGCACCCCACTCTGTACTCTT

GCCTGGAGAATCCATGA TGAGAGCCTGGTAGGCTGCAGTCCATGGGGTCACACAGAGTCGGACATGACTGAGCGACT

TCACTTTCACTTTTCAATTT CATGCATTGGAGCCGGAAATGGCAACCCACTCCAGTGTTCTTGCCTGGAGAATCCCAGGG

ATGGGGAAGCCTGGTGGGCT GCTGTCTATGGGGTCGCAGAGAGTCAGACACGACTGAAGTGACTTAGCAGCAACCTTCTG

GAATAAACGCCTCAGGCTTT AAACTCTGGCTTGACCATTCACTAGCCATGGGATCCACTAGAGTCGACCTGCAGGCATGCA

AGC

DNA Alignment

How Does Molecular Cloning Work?

Cloning of any DNA sequence involves the introduction of a foreign piece of DNA into an extrachromosomal element (cloning vector) of an organism which then produces copies of the vector as it replicates itself, thereby amplifying the DNA of interest. The whole process can be summarized in the following steps: fragmentation, ligation, transfection, screening/selection, and conformation of insert.

What is a Phylogeny ?

The evolutionary relationships among organisms; the patterns of lineage branching produced by the true evolutionary history of the organisms being considered. Many of the phylogenies you encounter are the "family trees" of groups of closely related species, but we can also use a phylogeny to depict the relationships between all life forms

What is a phylogeny ?

A phylogeny, or evolutionary tree, represents the evolutionary relationships among a set of organisms or groups of organisms, called taxa (singular: taxon). The tips of the tree represent groups of descendent taxa (often species) and the nodes on the tree represent the common ancestors of those descendents. Two descendents that split from the same node are called sister groups. In the tree below, species A & B are sister groups — they are each other's closest relatives.

What is a phylogeny ?

Many phylogenies also include an outgroup — a taxon outside the group of interest. All the members of the group of interest are more closely related to each other than they are to the outgroup. Hence, the outgroup stems from the base of the tree. An outgroup can give you a sense of where on the bigger tree of life the main group of organisms falls. It is also useful when constructing evolutionary trees.

Phylogenetic Classification

Conclusion

1. Molecular approach is decisive for future evaluations in cyanobacterial taxonomy.

However: 2. The stable phenotype features are in conformity with

molecular studies. – The molecular studies proved (i) the existence of natural

clusters, which correspond more or less to the traditional concept of genera or “macrospecies”, but also (ii) the very wide diversity inside of traditional species (two quite identical strains/populations were not yet found).

– Numerous stable infrageneric morphotypes exist in nature, which are ecologically restricted and well recognizable and different from one another.

Conclusion

– Molecular evaluation must be combined with evaluation of phenotype and ecological characters.

- The species concept is always more or less conventional, and now in cyanobacteria unclear; it is necessary to tend to such definition, which can be designated as “evolutionary and phenotypically natural units among cyanoprokaryotes”, recognizable in nature and/or in culture.

– The study of diversification, variability, stability and ecological plasticity of natural populations is highly desirable and necessary for ecological and taxonomic research.

Refernces

1- http://cyanobacteries.pagesperso-orange.fr/pages/Glossaire/Glossaire.htm

2- http://www.promega.com/resources/product-guides-and-selectors/protocols-and-applications-guide/pcr-amplification/

3- http://www.methodbook.net/dna/agarogel.html

http://www.wiley.com/college/pratt/0471393878/student/animations/dna_sequencing/index.html