Simplified and Semiautomated <i>Microcystis aeruginosa</i> Cell Enumeration Method Using Brightfield Microscopy

This manuscript presents an innovative semiautomated method to quantify Microcystis aeruginosa samples in a rapid and accurate manner using an automated microscope with a brightfield and fluorescent mode in conjunction with a MATLAB algorithm. A Petroff-Hausser counting chamber was used to mount and count bacteria cells, which allowed precise quantification of sampled volumes for concentration estimations. To the best of the authors’ knowledge, no Petroff-Hauser enumeration technique of Microcystis aeruginosa exists. Cell concentrations obtained from the microscope images were compared with cell concentrations obtained via flow cytometry. Results suggest that the microscope method underestimated cell concentrations in comparison to flow cytometer results but showed strong linear correlations (R2≈0.99). It was found that a higher number of cells per field-of-view on the microscope counting chamber correlated to higher accuracy and precision in concentration results, which could be achieved by concentrating the samples via centrifugation. Analogous concentrations between the two methods were found when the number of cells per field-of-view was ∼2,900.