Treponema pallidum

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.