Characterisation of growth parameters for the extremely acidophilic archaeon Ferroplasma acidiphilum DSM 12658 using a two-step turbidimetric growth measurement method

The acidophilic archaeon Ferroplasma acidiphilum exhibits remarkable adaptations to life in highly acidic environments. Nevertheless, the investigation of its molecular biology is challenging because of the slow growth of the organism, low biomass yield, and limitations of standard growth measurement techniques caused by iron oxidation.

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  A novel two-step turbidimetric growth measurement (2TGM) method was developed to address the shortcomings associated with iron precipitation in culture media. The method comprises two distinct preparation steps.

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  The initial 2TGM step involves centrifuging culture samples at high speed to remove F. acidiphilum cells and iron precipitates, thus preparing a blank.

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  The second 2TGM step involves centrifuging the culture at a lower speed with the objective of selectively removing iron precipitates, thus allowing F. acidiphilum cells to remain suspended in the supernatant. This preparation enables subsequent measurement of cell density.

A study on the growth of F. acidiphilum showed a standard logistic pattern with a 35-h lag phase, approximately 9-h doubling time, and 0.042 OD carrying capacity. A new two-step turbidimetric growth measurement (2TGM) method overcomes limitations of existing approaches, enabling further investigation of F. acidiphilum.