Foraminiferal Ultrastructure: A perspective From Fluorescent and Fluorogenic Probes

Abstract

Microscopy techniques have been widely applied to observe cellular ultrastructure. Most of these techniques, such as transmission electron microscopy, produce high‐resolution images, but they may require extensive preparation, hampering their application for in vivo examination. Other approaches, such as fluorescent and fluorogenic probes, can be applied not only to fixed specimens but also to living cells when the probes are nontoxic. Fluorescence‐based methods, which are generally relatively easy to use, allow visual and (semi)quantitative studies of the ultrastructural organization and processes of the cell under natural as well as manipulated conditions. To date, there are relatively few published studies on the nearly ubiquitous marine protistan group Foraminifera that have used fluorescent and fluorogenic probes, despite their huge potential. The aim of the present contribution is to document the feasible application of a wide array of these probes to foraminiferal biology. More specifically, we applied fluorescence‐based probes to study esterase activity, cell viability, calcium signaling, pH variation, reactive oxygen species, neutral and polar lipids, lipid droplets, cytoskeleton structures, Golgi complex, acidic vesicles, nuclei, and mitochondria in selected foraminiferal species.

Assessing the Cadmium Effects on the Benthic Foraminifer Ammonia cf. parkinsoniana: An Acute Toxicity Test

“…The CHB is a fluorogenic probe that passes through the cell membrane, and once within the cell, it is transformed into cell membrane-impermeant reaction products. This probe with blue excitation/emission spectra (353/466 nm maxima) has been used to check the viability of benthic foraminifera [27]. Other fluorescence-based methods have been used to assess the viability of specimens, as the widely used CellTracker Green.…”

“…The selection of these concentrations was based on a background level of Cd-uncontaminated coastal seawater and marine sediment (as well as previous toxicological studies (acute toxicity and sublethal effect) (i.e., [17] and reference therein). (353/466 nm maxima) has been used to check the viability of benthic foraminifera [27]. Other fluorescence-based methods have been used to assess the viability of specimens, as the widely used CellTracker Green.…”

SiR-actin-labelled granules in foraminifera: patterns, dynamics, and hypotheses

“…Saprolegnia ferax (Geitmann and Emons, 2000), Phytophthora infestans (Meijer et al, 2014), as well as in yeast, Saccharomyces cerevisiae (Moseley and Goode, 2006;Rodal et al, 2005;Waddle et al, 1996;Winter et al, 1997), where they are abundant in buds. They are referred to as cortical actin patches in budding yeast and S. ferax (Geitmann and Emons, 2000) or actin plaques in P. infestans (Meijer et al, 2014). In these organisms they occur alongside different actin structures such as actin cables or rings.…”

“…In these organisms they occur alongside different actin structures such as actin cables or rings. Fluorescent images of Saprolegnia ferax (Geitmann and Emons, 2000) indicate that actin patches have a globular shape and diameters of approx. 0.5 µm.…”

“…The maximum velocity of actin patches observed in yeast is 1.9 µm s −1 (Waddle et al, 1996), thus it is significantly lower than the velocity of actin granules in foraminifera. Cortical actin patches are most likely involved in endocytosis (Moseley and Goode, 2006) and cell growth (Geitmann and Emons, 2000). For instance in budding yeast actin patches are present during budding within the daughter cell.…”