PHYSIOLOGY OF SUBCELLULAR LIFE FORMS

Table of contents :



As subcellular life forms are obligate parasitic organisms, their physiology is strictly dependent on host cell biology and so often on their pathogenicity. Click here for more informations on those causing Homo sapiens diseases.
 

  •  virions => viruses : a small infectious pathogen composed of one or more nucleic acid molecules usually surrounded by a protein coat when outside the host cell. The 7th ICTV revision lists about 1550 different species
  • Web resources :
  • Subviral agents or unconventional viruses
  • Plasmids : a small autonomously replicating circular molecule of cyclic supercoiled dsDNA (4,350-240,000 bp) that is devoid of protein and not essential for the cell growth or survival of its host (Bacteria, Protozoa, Plantae or Metazoa) : in fact they can be eliminated by the host cell (curing) with no apparent damage to cell survival. It may exist free in the cytoplasm (extrachromosomal) or integrated in the host chromosome (episome). Its replication may be parallel (stringent control) or not parallel (relaxing control) to that of the cell chromosome(s), leading respectively to one only or more than one (up to 100) copies per cell. If 2 plasmids have the same replication repressor they cannot exist in the same cell (compatibility and incompatibility groups) : further every plasmid inhibits the expression of the pilus receptor OmpA preventing the income of other plasmids through conjugation (surface exclusion). Plasmids can be transferred from one cell to another by conjugation and by transduction. Plasmids may be classified according to...
  • mobile genetic elements (MGE) : a sequence of DNA that moves within their host's genome from one position to another integrating itself by transpositional recombination.
  • Web resources
  • Bibliography

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