Genetic transfer

These facts do not agree with the assumption that organisms evolved in straight lines. Since the Darwinian era, it has been usual to use the term genetic transfer to refer to the transmission of information within a species. However, for more than 30 years, phenomena have been observed which show that gene transfer between species of life forms is also possible. 

Over time, the progenotes evolved into more complex cellular structures that had a lower mutation rate and a much slower rate of lateral genetic transfer among cells. This was followed by evolution of cellular subsystems, adding a new level of cellular complexity. From these cells came the three great domains of living organisms the Eubacteria, Archaea, and Eukarya. 

Multidrug resistance (Mdr) is a serious problem in enteric and other Gramnegative bacteria [41, 71, 273-283] (Table 4.17). As distinct from plasmid-mediated resistance, described above, Mdr is a term employed to describe a resistance mechanism by genes that comprise part of the normal cell genome. These genes are activated by induction or mutation caused by some types of stress, considered below. Because the genes are ubiquitously distributed, there is no need for genetic transfer. 

Second, microbial chemical transformations are accomplished by means of enzymes, proteins that act as catalysts. Catalysts bind with reactants and hold them in such an orientation that they more readily react. The products of the reaction are then released, leaving the catalyst ready to facilitate another transformation. (It is possible for an enzyme to be destroyed if a chemical mimics the proper substrate sufficiently to bind, but fails to react and subsequently release from the enzyme.) Because each enzyme is produced in response to a section of the genetic code (DNA) in the organism and many enzymes are extremely specific, it is possible that some strains of a species of bacteria may accomplish a certain chemical transformation while other individuals cannot. By using modern techniques of molecular biology, scientists can insert specific biotransformation capabilities into bacteria by means of genetic transfer. This procedure is easiest if the genetic material is associated with plasmids, which are small circular molecules of DNA that can exist independently within a bacterial cell. 

Gurtler V, Mayall BC (2001) Genetic transfer and genome evolution in MRSA. Microbiology 147 3195-3197... 

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