Treponema pallidum

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Treponema Pallidium
Scientific classification
Kingdom: Eubacteria Phylum: Spirochaetes Class: Spirochaetes Order: Spirochaetales Family: Spirochaetacae Genus: Treponema Species: T. pallidium

Genome structure

Treponema pallidum is a prokaryote with one of the smaller genomes. The organism has many processes that are similar and required for other organisms although it is dependent on the host for its survival. Like other eukaryotes it undergoes transcription, translation, replication, repair and has restriction- modification systems. Its genomic sequence is very close to that of Borrelia burgdorferi that causes Lyme Disease in humans. The total genome sequence of the organism has 1,138,006 base pairs. The number of base pairs of the predicted coding sequences or of the number of open reading frames is 1041.

In order to repair DNA, T. pallidum goes through methods such as uvr exision repair, mutL/mutS mismatch repair, mut Y and dat.

It lacks type 4 topoisomerase that is involved in the process of chromosome segregation. Chromosome segregation in T. Pallidium is able to occur by another mechanism that involves binding hemimethylated DNA to the cytoplasmic membrane. The spirochete T. pallidium encodes for the homologs that are of the recF pathway that are involved in recombination.

Cell structure and metabolism

T. pallidium is a microaerophile and so it needs very little oxygen for growth. It does not have genes that code for enzymes that protect against oxygen toxicity. The enzymes are present in B. Burgdorferi and include superoxide dimutase, peroxidase or catalase. It however does have NADH oxidase which is the enzyme that utilizes oxygen in the organism.

It has an outer membrane a cytoplasmic membrane and it also consists of a thin peptidoglycan layer. Its outer membrane has relatively fewer integral membrane proteins. This permits the organism to evade the human response from the immune system.

The energy source for T. pallidium are mainly carbohydrates like glucose, galactose and glycerol. In tissue culture system the growth and multiplication of T. pallidium is only due to glucose, mannose and maltose. This has been an suggested due to experimental evidence. The T. pallidium has all the genes that code for enzymes that are required for the glycolytic pathway. T. pallidium has homologs of the enzymes phosphofructokinase and pyruvate kinase that are there in eubacterial organisms which use pyrophosphate for energy metabolism. It does not have any of the genes that code for substances required in the tricarboxylic acid cycle or of oxidative phosphorylation.

T.pallidium does not have a respiratory transport electron chain. ATP is therefore formed by substrate level phosphorylation and so the membrane potential is created by the reverse reaction of the enzyme ATP synthase. The ATP synthase in the T.pallidium is of the V1V0 type. It also has two operons of the V1V0 type and each contains seven genes.

Pathology

T. Pallidium is the causative agent of syphilis. It is transmitted through humans and cause diseases and can causes damages and previous damage done by the organism cannot be cured. It is only transmitted sexually. It can be transmitted from mother to baby. The disease it transmitted by sexual contact and it does not spread by using things that are used by others for regular purposes such as clothes, utensils, etc. The disease is spread from one person to another by contact with syphilis sores. It is spread through contact with syphilis sores that are caused by the organism. The sores can occur on the external anus, vagina, and internal anus and can also occur in the rectum. The primary stage of syphilis there is a chancre that is round and does not cause pain. It heals on its own and if the disease is not treated a person will go into the secondary and late phases of the disease. The sores can also occur in the mouth. Sometime it is not possible for a person to know whether the person has syphilis because sores occur in inside of the vagina and anus in males and females. So the person should be tested for syphilis. The secondary phase is associated with rash through out the body. If it is not treated the symptoms will go into the latent phase and it can cause damage to organs and it affect the coordination and affect the important organs and may even lead to death. Syphilis can be treated and the person at that time should avoid sexual contact. It just requires one dose of a intramuscular injection of penicillin.

The person infected with Syphilis has a higher risk of getting HIV. The spread of the disease can be preveted by using safe sex practices.

Neurosyphilis is a problem in patients who suffer from syphilis. It involves the Central nervous system. Tests are done by using the cerebrospinal fluid. There are four types of neurosyphilis Asymptomatic neurosyphilis, Meningovascular syphilis, General paresis and Tabes dorsalis. The last two forms are not quite common now.During Meningiovascular syphilis the person first experiences prodomal symptoms and then the person goes into the later stage. The disease can occur within 10 months or it might on an average even take 7 years to be expressed. The symptoms of the prodomal stage are behavioral changes and other problems are headache ,weakness numbness and insomnia. There can also be an inflammation of the arteries and the person can also suffer from stroke because there is less blood supply from the arteries.

References

Sheila A. Lukehart. Chapter 153. "Syphilis" in Dennis L. Kasper, Eugene Braunwald, Anthony S. Fauci, Stephen L. Hauser, Dan L. Longo, J. Larry Jameson, and Kurt J. Isselbacher, Eds.Harrison's Principles of Internal Medicine, 16th Edition