PhenoChip: A single-cell phenomic platform for high-throughput photophysiological analyses of microalgae

Abstract

Photosynthetic microorganisms are key players in aquatic ecosystems with strong potential for bioenergy production, yet their systematic selection at the single-cell level for improved productivity or stress resilience (“phenotyping”) has remained largely inaccessible. To facilitate the phenotyping of microalgae and cyanobacteria, we developed “PhenoChip,” a platform for the multiparametric photophysiological characterization and selection of unicellular phenotypes under user-controlled physicochemical conditions. We used PhenoChip to expose single cells of the coral symbiont Symbiodinium to thermal and chemical treatments and monitor single-cell photophysiology via chlorophyll fluorometry. This revealed strain-specific thermal sensitivity thresholds and distinct pH optima for photosynthetic performance, and permitted the identification of single cells with elevated resilience toward rising temperature. Optical expulsion technology was used to collect single cells from PhenoChip, and their propagation revealed indications of transgenerational preservation of photosynthetic phenotypes. PhenoChip represents a versatile platform for the phenotyping of photosynthetic unicells relevant to biotechnology, ecotoxicology, and assisted evolution.

Microfluidic Platforms Designed for Morphological and Photosynthetic Investigations of Chlamydomonas reinhardtii on a Single-Cell Level

“…Recently, Behrendt et al [ 36 ] developed “PhenoChip”, a compact and versatile microfluidic platform to enable rapid, high-throughput phenotyping of Symbiodinium and cyanobacteria based on their photosynthetic performance under relevant environmental conditions. By applying the Microscopy version of the Imaging PAM M-series Chl a fluorometer, they could determine the F V /F M values of single Symbiodinium cells, and use it to identify cells with elevated resilience toward high temperature.…”

A microscopy-compatible temperature regulation system for single-cell phenotype analysis – demonstrated by thermoresponse mapping of microalgae

“…Our a priori assumption for experiments i) and ii) was that cells exposed to short-term thermal stress (< 6h) would not be able to acclimate their photometabolism to elevated temperatures, whereas cells exposed to long-term thermal stress (> 6h) would have enough time to do so. Based on previous works [26][27][28] we also expected considerable heterogeneity among single cells of Symbiodinium in their ability to withstand thermal stress events.…”

“…A well size of 20 μm yielded a good compromise between loading efficiency, multiple cell occupancies and loss rate of cell populations for the investigated cell type as discussed previously. 26 Double and triple occupancies per-well were accepted in order to obtain higher loading efficiencies. Only wells containing single cells were used for the analysis, identified during post-processing using standard image analysis tools.…”

Possible Functional Roles of Patellamides in the Ascidian-Prochloron Symbiosis

“…An important question, particularly in relation to the latter point is, why there is a large variety of patellamide derivatives with subtle structural differences, and how important the emerging structure-function correlations of the copper-patellamide complexes are for the ascidian-Prochloron system. Various methods including chemical imaging (e.g., imaging mass-spectrometry and spatial metabolomics) [132], fluorescence-based assays [102], microfluidic technologies [133], and synchrotron-based spectroscopy [126] might provide the ability to assess the importance of the behavior of the copper(II)-patellamide complexes under in vivo like conditions. Such efforts could provide answers to long held questions on the natural function of patellamides and patellamide-copper(II) complexes as well as the problems to cultivate Prochloron.…”