Patricia L. Walne

An Evaluation of a Possible Phylogenetic Relationship Between the Euglenophyta and Kinetoplastida

Winthout close phylogenetic ties to any of the other algae, the Euglenophyta are a taxonomic enigma. The argument is made here that the euglenophytes have extensive morphological homology with the zooflagellte trypanosomatids, bodonids, andIsonema. A phylogenetic sequence is postulated linking these group; the available data suggest that the euglenophytes had their origin in these zooflagellates and that the introduction of the chloroplast and a phototrophic mode of nutrition was a relatively late step in this evolutionary process.

The comparative ultrastructure and possible function of eyespots: Euglena granulata and Chlamydomonas eugametos

SummaryThe structure of Euglena granulata and Chlamydomonas eugametos has been studied using polarization and electron microscopy, cinematography, and chemical extraction procedures, with the main focus on the structure of the eyespot.The 50–60 granules which form the extrachloroplastic eyespot of E. granulata are large bodies, up to 1200 mμ in diameter. They are found in the cytoplasm near the base of the reservoir and are associated with the parabasal body which contains a large crystal. The eyespot granules are contained within membranes having a unit membrane structure; 2 or 3 are usually present in a single eyespot packet; microtubules are also contained within the packet. The eyespot granules have the structure of a positive spherite and clearly exhibit birefringence; this structure is modified by fixation.The granules of the chloroplastic eyespot of C. eugametos are about 75 mμ in diameter and are contained within the chloroplast in an ordered array. Occasionally, the eyespot contains elongate or helical bodies mixed with the granules. Extraction with organic solvents caused the removal of materials which formed the eyespot granules as well as that of the osmophilic globules in the chloroplasts.Several hypotheses which concern the function of the eyespots in these and other species are discussed in the light of our results. the possible origin and demise of the eyespot granules are also discussed.

ENTOSIPHON SULCATUM (EUGLENOPHYCEAE): FLAGELLAR ROOTS OF THE BASAL BODY COMPLEX AND RESERVOIR REGION1,2

The flagellar root system of Entosiphon sulcatum (Dujardin) Stein (Euglenophyceae) is described and compared with kinetoplastid and other euglenoid systems. An asymmetric pattern of three microtubular roots, one between the two flagellar basal bodies and one on either side (here called the intermediate, dorsal, and ventral roots), is consistent within the euglenoid flagellates studied thus far. The dorsal root is associated with the basal body of the anterior flagellum (F1) and lies on the left dorsal side of the basal body complex. Originating between the two flagellar basal bodies, and associated with the basal body of the trailing flagellum (F2), the intermediate root is morphologically distinguished by fibrils interconnecting the individual microtubules to one another and to the over lying reservoir membrane. The intermediate root is often borne on a ridge projecting into the reservoir. The ventral root originates near the F2 basal body and lies on the right ventral side of the cell. Fibrillar connections link the membrane of F2 with the reservoir membrane at the reservoircanal transition level. A large cross‐banded fiber joins the two flagellar basal bodies, and a series of smaller striated fibers links the anterior accessory and flagellar basal bodies. Large nonstriated fibers extend from the basal body complex posteriorly into the cytoplasm.

FLUOROMETRIC EVIDENCE FOR FLAVINS IN ISOLATED EYESPOTS OF EUGLENA GRACILIS VAR. BACILLARIS

Abstract— Fluorometric evidence suggesting the presence of flavins in isolated eyespots of Euglena gracilis var. bacillaris is reported for the first time. Fluorescence spectra of eyespots and flavin standards show maxima at 540nm and 530nm, respectively. Excitation spectra show matching major peaks at 360–370 nm and at 450nm. The addition of riboflavin standard to eyespot samples increases fluorescence intensity without major corresponding shifts in wavelength maxima. Photolysis of eyespot samples in the presence of EDTA effects a decrease in the fluorescence intensity; the fluorescence is quantitatively restored to its initial value by bubbling the photolyzed solution with air. Preliminary quantitative data, obtained by fluorescence measurements, indicate the presence of ca. 5 × 10‐4μg flavin/ml eyespot sample. While flavins have been hypothesized to be components of the photoreceptor system, they have been reported previously only in the paraflagellar bodies of intact cells. Emission and excitation data obtained by us for eyespots are similar to those previously reported by other investigators for paraflagellar bodies, but our studies now suggest the presence of flavins also in Euglena eyespots.

In vivo photocycle of the Euglena gracilis photoreceptor.

We present the light-induced photocycle of the paraflagellar swelling of Euglena gracilis. The kinetics of this process was reconstructed by sampling its fluorescence emission and switching the excitation light from 365 nm to 436 nm. Stable intermediates in the photocycle were manifested. The measured millisecond resolution kinetics best fits a Michaelis-Menten equation. The data provide strong evidence that the paraflagellar swelling, a three-dimensional natural crystal of a light-detecting protein, is the true Euglena photoreceptor.

ULTRASTRUCTURE OF THE FLAGELLA OF THE COLORLESS PHAGOTROPH PERANEMA TRICHOPHORUM (EUGLENOPHYCEAE).II. FLAGELLAR ROOTS1

Peranema trichophorum (Ehrenberg) Stein, a colorless phagotrophic euglenoid flagellate, has a typically euglenoid microtubular root complement. Striated root components, relatively uncommon in euglenoids, are connected to the basal bodies and to a microtubular root.

The photoreceptor protein of Euglena gracilis

We isolated the photoactive protein Erh, isolated from the photoreceptor of the unicellular photosynthetic flagellate Euglena gracilis. It is a 27 kDa protein with a photocycle resembling that of sensory rhodopsin, but with at least one stable intermediate. We recorded the absorption spectrum of the parent form of this protein both under native form and in the presence of hydroxylamine and sodium borohydride, and the fluorescence spectra of both the parent and intermediate forms. We suggest that Erh is a rhodopsin‐like protein and propose a simple photocycle. This protein shows optical bistability, without thermal deactivation.

Cytological and taxonomic studies of the Euglenales. II: Comparative microarchitecture and cytochemistry of envelopes of Strombomonas and trachelomonas

Envelopes of Strombomonas conspersa, like those of Trachelomonas, may range in colour from hyaline to dark brown. Cytochemical staining with Alcian Blue reveals differences between light and dark envelopes of both genera: acidic and sulphated glycosaminoglycans (mucopolysaccharides) are present in all the organic matrices; however, in dark envelopes the sulphate groups are masked by the Mn and are detectable only when the metal is removed. The TEM and EM-EDS comparative studies of the microarchitecture and elemental composition of envelopes of Strombomonas conspersa and several species of Trachelomonas show similar results: hyaline envelopes are characterized by unmineralized strands that anastomose to form a complex reticulum, whereas dark envelopes, heavily mineralized with Mn, are composed of dense needle-like components enmeshed in a mucilaginous matrix. In the light of these findings, we propose that Strombomonas conspersa be removed to its original taxonomic position in the genus Trachelomonas, as T...

TRACHELOMONAS HISPIDA VAR. CORONATA (EUGLENOPHYCEAE). III. ENVELOPE ELEMENTAL COMPOSITION AND MINERALIZATION1,2

This report is the first direct demonstration of Mn deposition in envelopes (loricas) of Trachelomonas in culture. The envelopes of Trachelomonas hispida var. coronata Lemm. were analyzed for elemental composition by X‐ray fluorescence spectrometry (XRF), atomic absorption spectrophotometry (AA), and electron microscopic, energy‐dispersive X‐ray spectroscopy (EM‐EDS). The envelopes contained extensive deposits of manganese (20–60 wt. %) and lesser amounts of Si, Ca and either Ba or Ti, the last three together totalling less than 5% by weight. The average amount of Mn per envelope was estimated at 1.5 × 10−10 g. Traces of Na, K, P, S and Cl were also detectable. Biomineralization of envelopes was studied by comparison of envelope substructure and composition in lightly colored, golden and dark brown envelopes that were isolated by micromanipulation, processed individually or in groups, and analyzed by SEM, TEM, EM‐EDS, and scanning transmission EM‐EDS (STEM‐EDS). Dark envelopes were thicker (1–4 μm), more ornate and less porous than light envelopes, but the ultrastructure of the two was similar. In both types of envelopes, distribution and thickness of Mn‐containing fibrillar to needle‐like microcrystallites were similar. However, dark envelopes contained a greater density of granular deposits around the needle‐like microcrystallites than did light envelopes. Dark envelopes contained 2–40 times more Mn than did light envelopes, but since envelope mass is proportionately greater, Mn concentrations were similar. Our results suggest that the extent of mineralization depends upon the amount of mucilage secreted. Biomineralization studies with Trachelomonas offer the rare advantage that mineral deposition occurs extracellularly, and not within membrane‐bound compartments as in many other unicellular model systems.

Microarchitecture and elemental spatial segregation of envelopes ofTrachelomonas lefevrei (Euglenophyceae)

SummaryEnvelopes of the euglenoid flagellate,Trachelomonas lefevrei may range in color from hyaline to golden to dark brown and may be variously ornamented with spines, papillae and puncta. Elemental composition affects both envelope color and microarchitecture, which may be granular and/or microcrystalline. TEM-EDS microanalyses of granular envelopes or regions show Fe as the predominant element, whereas Mn is the predominant element in envelopes or regions with high concentrations of needle-like microcrystallites. In envelopes composed of both structural components, there is a spatial segregation of Fe and Mn that corresponds to the distribution of the granular and/or microcrystalline entities. Extraction of the needle-like components with leucoberbelin blue indicates that they are Mn oxides. Quantitative elemental analyses show shifting ratios of Mn: Fe that correlate with envelope color and microarchitecture. This is the first direct demonstration both of such a spatial segregation of elements and of the presence of Mn oxides in envelopes ofTrachelomonas.