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The cytochrome complement of Haemophilus parasuis
Insights
Haemophilus parasuis synthesizes various cytochromes, including CO- and NO-binding types, with potential roles as oxidases. Bacterial growth conditions and oxygen availability regulate this cytochrome synthesis.
Area of Science:
- Microbiology
- Biochemistry
- Bacterial Physiology
Background:
- Haemophilus parasuis is a significant pathogen in swine.
- Understanding bacterial respiratory chain components is crucial for metabolic studies.
Purpose of the Study:
- To characterize the cytochrome content of Haemophilus parasuis.
- To investigate the localization and redox properties of synthesized cytochromes.
- To explore factors influencing cytochrome synthesis in H. parasuis.
Main Methods:
- Spectral analysis of subcellular fractions.
- Redox potential determination.
- Osmotic shock treatment for localization studies.
Main Results:
- H. parasuis synthesizes membrane-bound and soluble CO- and NO-binding c-type cytochromes.
- Cytochromes d, a1, and o were identified as potential oxidases.
- A soluble, low-potential cytochrome c was identified in the extracytoplasmic space.
- Cytochrome content is influenced by growth medium and growth phase.
Conclusions:
- H. parasuis possesses a complex cytochrome system involved in respiration.
- Oxygen availability, bacterial concentration, and growth rate likely regulate cytochrome synthesis.
- The extracytoplasmic location of soluble cytochrome c suggests a role in electron transport or signaling.
Abstract:
Spectral analyses with subcellular fractions derived from Haemophilus parasuis demonstrated that this organism could synthesize membrane-bound and soluble CO- and NO-binding c-type cytochromes in addition to the membrane-bound cytochromes d, a1, b, and c; cytochromes d, a1, and o were identified as potential oxidases. The membrane-bound and soluble CO- and NO-binding cytochromes c were not spectrally variant cytochromes c, and the redox properties of the soluble cytochrome (reducible by NADH but not by succinate or ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine) suggested that it, at least, was a low-potential cytochrome; up to 68% of the soluble cytochrome c could be released from the organisms by osmotic-shock treatment, demonstrating its extracytoplasmic location. The cytochrome content of H. parasuis was influenced by both the composition of the growth medium and the phase of growth; it is suggested that the bacterial concentration and growth rate, and therefore the availability of oxygen, regulated cytochrome synthesis.