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Improved method for enumerating sulfate-reducing bacteria using optical density.

Bernardez LA, de Andrade Lima LR - MethodsX (2015)

Bottom Line: The photometric determination of bacterial concentration can be affected by secondary scattering and other interferences.The conventional growth medium for sulfate-reducing bacteria (SRB) has iron that precipitates as iron sulfides, a dark precipitate which is useful to indicate bacterial activity.It was observed a large slope in the linearized fit equation, and the acidified solution does not change the integrity of the SRB cells after the treatment.•The results of the kinetic experiments, including the bacterial growth time evolution, demonstrate the applicability of the method.

View Article: PubMed Central - PubMed

Affiliation: Graduate Program of Industrial Engineering, Federal University of Bahia, Brazil.

ABSTRACT
The photometric determination of bacterial concentration can be affected by secondary scattering and other interferences. The conventional growth medium for sulfate-reducing bacteria (SRB) has iron that precipitates as iron sulfides, a dark precipitate which is useful to indicate bacterial activity. However, iron hydroxides also precipitate at high pH values and the presence of these precipitates interferes considerably in the optical density of the solution affecting estimates of the cell population thus seriously limiting the use of the conventional method. In this method a modification of the current method improves the measurement of the optical density of a solution with SRB cells. •The method consists of an acidification with hydrochloric acid of a sample of a mixed culture of SRB enriched from the produced water from oil fields to pH below 2.•The results show that the relationship between the bacterial dry mass and absorbance is exponential in the observed range. It was observed a large slope in the linearized fit equation, and the acidified solution does not change the integrity of the SRB cells after the treatment.•The results of the kinetic experiments, including the bacterial growth time evolution, demonstrate the applicability of the method.

No MeSH data available.


Cell concentration (DW) as a function of optical density (absorbance at 600 nm).
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fig0005: Cell concentration (DW) as a function of optical density (absorbance at 600 nm).

Mentions: During the kinetic experiment samples were withdrawn at suitable time intervals and then after acidification the biomass concentrations are evaluated using the calibration curve in Fig. 1. The sulfate and sulfide solution content was measured by turbidimetric methods. Barium sulfate was added to the samples to precipitate the sulfate ions as barium sulfate and copper sulfate was added to precipitate the sulfide ions as copper sulfide. For the pH measurements a pH meter calibrated using buffer solutions of pHs of 4 and 7 was used. The redox potentials were measured using an ORP electrode with an internal Ag/AgCl reference electrode [1], [2].


Improved method for enumerating sulfate-reducing bacteria using optical density.

Bernardez LA, de Andrade Lima LR - MethodsX (2015)

Cell concentration (DW) as a function of optical density (absorbance at 600 nm).
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4487919&req=5

fig0005: Cell concentration (DW) as a function of optical density (absorbance at 600 nm).
Mentions: During the kinetic experiment samples were withdrawn at suitable time intervals and then after acidification the biomass concentrations are evaluated using the calibration curve in Fig. 1. The sulfate and sulfide solution content was measured by turbidimetric methods. Barium sulfate was added to the samples to precipitate the sulfate ions as barium sulfate and copper sulfate was added to precipitate the sulfide ions as copper sulfide. For the pH measurements a pH meter calibrated using buffer solutions of pHs of 4 and 7 was used. The redox potentials were measured using an ORP electrode with an internal Ag/AgCl reference electrode [1], [2].

Bottom Line: The photometric determination of bacterial concentration can be affected by secondary scattering and other interferences.The conventional growth medium for sulfate-reducing bacteria (SRB) has iron that precipitates as iron sulfides, a dark precipitate which is useful to indicate bacterial activity.It was observed a large slope in the linearized fit equation, and the acidified solution does not change the integrity of the SRB cells after the treatment.•The results of the kinetic experiments, including the bacterial growth time evolution, demonstrate the applicability of the method.

View Article: PubMed Central - PubMed

Affiliation: Graduate Program of Industrial Engineering, Federal University of Bahia, Brazil.

ABSTRACT
The photometric determination of bacterial concentration can be affected by secondary scattering and other interferences. The conventional growth medium for sulfate-reducing bacteria (SRB) has iron that precipitates as iron sulfides, a dark precipitate which is useful to indicate bacterial activity. However, iron hydroxides also precipitate at high pH values and the presence of these precipitates interferes considerably in the optical density of the solution affecting estimates of the cell population thus seriously limiting the use of the conventional method. In this method a modification of the current method improves the measurement of the optical density of a solution with SRB cells. •The method consists of an acidification with hydrochloric acid of a sample of a mixed culture of SRB enriched from the produced water from oil fields to pH below 2.•The results show that the relationship between the bacterial dry mass and absorbance is exponential in the observed range. It was observed a large slope in the linearized fit equation, and the acidified solution does not change the integrity of the SRB cells after the treatment.•The results of the kinetic experiments, including the bacterial growth time evolution, demonstrate the applicability of the method.

No MeSH data available.