Evaluation of image analysis and laser granulometry for microbial cell sizing

Abstract

A direct cell size measurement technique and an image analysis based sizing method were developed. The former consisted of a manual size measurement of the two-dimensional cell images on a video screen, with automatic data recording. This method was chosen as the reference. The latter, a semiautomatic method took advantage of a commercial computer program designed for image processing and particle morphology analysis. It gave average and median size values which were compatible with the manual method. However, the performance of these time consuming methods is limited. Hence, the laser granulometry technique, intrinsically far more powerful while capable of analysing millions of sample objects in a short time delay, was applied. The comparison revealed that this method gives too low size values, particularly in disagreement with the known dimensions of the bacterial (Zymomonas mobilis) cells. A size correction method was developed to realign the granulometry results of Z mobilis cell samples with those of the direct manual measurement method.

Mechanisms of Syneresis in Rennet Curd without Mechanical Treatment

“…The program OP-TISCAN (Graftek, Aix-en Provence, France) enabled us to visualize captured images, adjust their luminosity and contrast and save them as a file. The program OPTILAB PRO (Graftek, Aix-en Provence, France) was used to improve the quality of images using, first, linear and non-linear filters, and, second, binary processing such as image erosion, dilatation, opening and closing (Vaija et al, 1995). To access quantitative analysis and to evaluate the characteristics of curd pieces, pattern recognition options were used.…”

“…We developed an original method for syneresis evaluation based on image analysis which enabled direct monitoring of curd shrinkage using a semiautomatic size analysis method (Vaija et al, 1995). In order to evaluate the potential of this approach, we undertook to follow the effects of cutting on curd syneresis by using image analysis in parallel with the usual tracer method (Zviedrans and Graham, 1981).…”

Biomass Quantification by Image Analysis

“…For the later, a detachment is necessary, with risks on the physiological state of the cells and of partial detachment. Even for yeast cells the agreement between the different methods is difficult to reach, due to shape factor [29,97].…”

“…Saccharomyces cerevisiae yeast cells are mostly assumed to be prolate ellipsoids [74] 4pW 2 F V = 04 (25) 3 or even spheres [37,96]. Vaija et al [97] assume that Saccharomyces cerevisiae mother cell is a prolate ellipsoid with a spherical bud. A more detailed volume determination has been used by Huls et al [29] for the same yeast but their technique, based on narrow slices perpendicular to the main axis of the cell, is not fully automated as the operator interactively selects the cell to analyze.…”

Sizing and counting of saccharomyces cerevisiae floc populations by image analysis, using an automatically calculated threshold

“…The usefulness of manually operated procedures is further restricted due to the high number of images necessary to obtain statistically significant data. Other methods, such as flow cytometry (Al-Rubeai et al, 1995;Lopez-Amor6s et al, 1994;Peterson and Patkar, 1992) and laser granulometry (Vaija et al, 1995), are capable of analyzing millions of sample objects. However, flow cytometry suffers from the difficulty of staining cell aggregates, used mostly with individual cells (Peterson and Patkar, 1992), and laser granulometry has been found to give too low values when evaluating cell size (Vaija et al, 1995).…”