The uptake of DNA is generally non-sequence specific, although in some species the presence of specific DNA uptake sequences may facilitate efficient DNA uptake.Īrtificial competence can be induced in laboratory procedures that involve making the cell passively permeable to DNA, by exposing it to conditions that do not normally occur in nature. Pilin may be required for competence however, its role is uncertain. In Gram-negative cells, due to the presence of an extra membrane, the DNA requires the presence of a channel formed by secretins on the outer membrane. Only single-stranded DNA may pass through, one strand is therefore degraded by nucleases in the process, and the translocated single-stranded DNA may then be integrated into the bacterial chromosomes by a RecA-dependent process. The DNA first binds to the surface of the competent cells on a DNA receptor, and passes through the cytoplasmic membrane via DNA translocase. However, most of them share common features that involve related proteins. GRAM-POSITIVE AND GRAM-NEGATIVE DIFFERENCESĭue to the differences in structure of the cell envelope between Gram-positive and Gram-negative bacteria, there are some differences in the mechanisms of DNA uptake in these cells. The transport of the exogeneous DNA into the cells may require proteins that are involved in the assembly of type IV pili and type II secretion system, as well as DNA translocase complex at the cytoplasmic membrane. These naturally-competent bacteria carry sets of genes that provide the protein machinery to bring DNA across the cell membrane(s). Some species, upon cell death, release their DNA to be taken up by other cells however, transformation works best with DNA from closely-related species. DNA material can be transferred between different strains of bacteria in a process that is called horizontal gene transfer. There are two forms of competence: natural and artificial.Ībout 1% of bacterial species are capable of naturally taking up DNA under laboratory conditions more may be able to take it up in their natural environments. Competence refers to the state of being able to take up exogenous DNA from the environment. Introduction of foreign DNA into eukaryotic cells is often called “ transfection“.īacterial transformation may be referred to as a stable genetic change, brought about by the uptake of naked DNA (DNA without associated cells or proteins ). “ Transformation” may also be used to describe the insertion of new genetic material into nonbacterial cells, including animal and plant cells however, because “transformation” has a special meaning in relation to animal cells, indicating progression to a cancerous state, the term should be avoided for animal cells when describing introduction of exogenous genetic material. Transformation is one of three processes by which exogenous genetic material may be introduced into a bacterial cell the other two being conjugation (transfer of genetic material between two bacterial cells in direct contact), and transduction (injection of foreign DNA by a bacteriophage virus into the host bacterium). For transformation to happen, bacteria must be in a state of competence, which might occur as a time-limited response to environmental conditions such as starvation and cell density. Transformation occurs naturally in some species of bacteria, but it can also be effected by artificial means in other cells. Overall, the toxins produced by Gram-negative bacteria can cause many symptoms and complications, and treatment typically involves antibiotics and supportive care for any related symptoms or complications.\) LPS can contribute to sepsis and other conditions associated with Gram-negative bacterial infections. Lipopolysaccharides (LPS) are also part of the cell wall of Gram-negative bacteria and can stimulate the immune system to produce inflammation and other responses.
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