Image-Based Monitoring System for Green Algal Haematococcus pluvialis (Chlorophyceae) Cells during Culture

Abstract

The green microalga Haematococcus pluvialis accumulates the red pigment astaxanthin accompanied by morphological changes under stress conditions, including nutrient depletion, continuous light and high temperature. To investigate the physiological state of the algal cells, we developed the digital image-processing software called HaematoCalMorph. The software automatically outputs 25 single-cell measurements of cell morphology and pigments based on color, bright-field microscopic images. Compared with manual inspection, the output values of cell shape were reliable and reproducible. The estimated pigment content fits the values calculated by conventional methods. Using a random forests classifier, we were able to distinguish flagellated cells from immotile cells and detect their transient appearance in culture. By performing principal components analysis, we also successfully monitored time-dependent morphological and colorimetric changes in culture. Thus, combined with multivariate statistical techniques, the software proves useful for studying cellular responses to various conditions as well as for monitoring population dynamics in culture.

Hyperspectral imaging techniques for the characterization of Haematococcus pluvialis (Chlorophyceae)

“…, center column), which could be specified using HaematoCalMorph (Ohnuki et al. ). The culture spectrum was calculated by averaging cell spectra in the same sample.…”

“…RGB image files were processed with HaematoCalMorph (Ohnuki et al. ) as a test model to obtain information on recognized cell regions. Typical morphological changes during culturing were observed (Fig.…”

“…Recently, we developed an image‐based system for monitoring H. pluvialis cells (Ohnuki et al. ) in which we quantified cell morphology and pigments. Our system includes observation of algal cells under a bright‐field microscope and data processing with image‐processing software called “HaematoCalMorph.” With a combination of multivariate statistical techniques, it was possible to classify the cells into specific groups reflecting life‐cycle stages and to monitor dynamic changes in the culture.…”

“…Measuring algal morphology and the pigment content is important to monitor the physiological status of algal cells in culture. Recently, we developed an image-based system for monitoring H. pluvialis cells (Ohnuki et al 2013) in which we quantified cell morphology and pigments. Our system includes observation of algal cells under a bright-field microscope and data processing with image-processing software called "Haem-atoCalMorph."…”

Monitoring of Microalgal Processes

“…These data were used to recognize dead cells, estimate cellular pigment content, and monitor the transition of cells from one type to another [241].…”