Experiences with the Coulter counter in bacteriology

Area of Science:

• Microbiology
• Biophysics
• Analytical Chemistry

Background:

• Accurate enumeration of microbial populations is crucial in various scientific fields.
• Traditional methods like microscopy and culturing can be time-consuming and labor-intensive.
• Electronic particle counting offers a potentially faster and more objective alternative.

Purpose of the Study:

• To evaluate the efficacy of electronic particle counting for enumerating bacterial suspensions.
• To compare electronic counts with standard bacteriological and microscopic methods.
• To investigate the ability of electronic particle counting to differentiate between viable and non-viable bacterial cells.

Main Methods:

• Suspensions of viable and killed Staphylococcus aureus, Escherichia coli, and Serratia marcescens were prepared.
• Polystyrene spheres of known diameters were used as controls.
• Electronic counts were performed using a Model A Coulter Counter, with simultaneous comparison to standard bacteriological counts and microscopy.

Main Results:

• Electronic particle counting provided consistent results across different bacterial species.
• Distinct electrical characteristics and pulse patterns were observed for different bacterial populations.
• Live bacteria exhibited different pulse patterns compared to killed bacteria and inert particles, indicating viability assessment capability.

Conclusions:

• Electronic particle counting is a reliable method for enumerating bacterial suspensions.
• The technique can differentiate between viable and non-viable bacterial cells based on electrical properties.
• This method offers a valuable tool for microbial analysis, complementing traditional techniques.