A general account of Rickettsiae :
Howard Taylor Ricketts (1909) a medical scientist at the University of Chicago was the 1st do discover Rickettsiae while studying Rocky Mountain spotted fever. H.D Rochalima (1916) name the genus as Rickettsiae after the name of its discovery. He also names the species of Rickettsiae after the name of its discovery. He also names the species of Rickettsiae as Prowazekii in honor of another scientist Van Prowazekii in honor of Hamburg. Who also died while studying these diseases. The classical typhus fever. Hence the name of the Typhus genus is Rickettsiae prowazekii.
The general character of Rickettsia :
Rickettsia is a minute organism having a characteristic feature which is intermediate with virus and bacteria.
The character of Rickettsia resembling with bacteria:
(a) Like bacteria, Rickettsia contains both DNA and RNA.
(b) They always multiply by Binary fission.
(c) All metabolic activities are given by enzymes.
(d) Muramic acid is present in the cell wall of Rickettsia.
(e) Rickettsia is like coccus or bacillus 600X300μ in size.
(f) Both bacteria and Rickettsia are highly pleomorphic and visible under a light microscope.
(g) They are gram-negative.
(h) Both are sensitive to many antibiotics.
The character of Rickettsia resembling with the virus:
(a) Like virus Rickettsia always multiply with the host cytoplasm except for the organism of the spotted fever group which also grow within the nucleus of the host cell.
(b) The multiplied Rickettsia cells are liberated by the lysis of the host cell.
Structure of the Rickettsia:
(a) Like virus Rickettsia always multiply with the host cytoplasm except for the organism of the spotted fever group which also grow within the nucleus of the host cell.
(b) The multiplied Rickettsia cells are liberated by the lysis of the host cell.
Structure of the Rickettsia:
Rickettsia is nonmotile, small, in size range of 0.3 to 0.7μm in wide and 1to 5μm in length. Therefore they are much smaller than bacteria, They are spherical and rod-shaped and are gram-negative.
Generally, the multiplication is by binary fission. The daughter cell stays in the chain after fission to form a long chain-like structure. Cell wall made up of Muramic acid. The cell contains both DNA and RNA. The DNA is in the form of a double-strand. The invagination of the cell membrane indicates the presence of a mesosome. During the infection of the host, The Rickettsia cell is alive and very active. Once it has reached the phagocyte cell, It multiplied in the cytoplasm, fills up the cell completely. Finally, the Rickettsia cells are liberated into the body fluid of the host and came out by bursting the infected cells.
Metabolism: Purification and separation of Rickettsia cells are done for studying their metabolic path waste. It is a difficult process because of free cells of Rickettsia lost their viability. Extensive studies indicate that in energy metabolism, these cells are oxidized only one amino acid i.e; glutamate, other organic, and amino acid are not oxidized. Though this organism is not able to synthesize certainly smaller molecules needed for growth they have to obtain their food for the host. Co-enzyme like NAD and CoA are providing to this host cell.
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