Coleman AW

Comparison of Eudorina/Pleodorina ITS sequences of isolates from nature with those from experimental hybrids
AM J BOT 89 (9): 1523-1530 SEP 2002

Abstract:
Internal transcribed spacer (ITS) regions of nuclear ribosomal repeats were compared among 50 Eudorina and Pleodorina isolates and two Volvox species known to clade with Eudorina species. Of the six major subclades found, four containing Eudorina and Pleodorina illinoisensis isolates, one containing Eudorina and Pleodorina indica, and one containing Volvox gigas and V. powersii, the basal branching order remains uncertain, but the positioning of isolates known to mate was always as nearest neighbors on the terminal branches of the tree. Four hybrid clones from a cross of E. elegans with P. illinoisensis, known from chromosome counts to be products of the failure of meiosis at zygote germination, contain both parental ITS repeat regions, as expected. However, they have in addition both crossover and other variant ITS cistrons among their many repeats of ITS. Such variation is limited to terminal regions of helices, as recognized from knowledge of RNA transcript secondary structure. Proper alignment then utilizes all of the nucleotide positions; the hybrid variants appear in positions intermediate between their parents in the tree. In fact, such variants seem to be hallmarks of recent hybridization events, since they were not found in any of the other 50 isolates.

Tien CJ, Krivtsov V, Levado E, et al.

Occurrence of cell-associated mucilage and soluble extracellular polysaccharides in Rostherne Mere and their possible significance
HYDROBIOLOGIA 485 (1-3): 245-252 OCT 2002

Abstract:
The cell-associated mucilage and soluble extracellular polysaccharides (EPS) were investigated in a eutrophic freshwater lake (Rostherne Mere, Cheshire, U. K.) over up to 2 year annual cycles. Five particular lake algae (Anabaena spiroides Klebahn, Anabaena flos-aquae Brebisson ex Bornet & Flahault, Anabaena circinalis Rabenhorst, Microcystis aeruginosa Kutzing emend. Elenkin and Eudorina elegans Ehrenberg) were found to be the major contributors to cell-associated mucilage, particularly M. aeruginosa. Calculation of the total amount of cell-associated mucilage in the phytoplankton samples showed that it occupied 0.0001-0.007% (the latter during a bloom of Microcystis) of lake water volume within the epilimnion. Seasonal changes in the total volume of associated mucilage reflected the succession of mucilage-producing algal species in Rostherne Mere, which was closely correlated with the physico-chemical (temperature, oxygen, pH, nutrients) and biological (Secchi depth, phytoplankton) parameters within the lake. High levels of cell-associated mucilage present in the lake may have potential for binding metals or other ions in the aquatic environment. Colourimetric determination of the concentration of soluble EPS revealed concentrations of between 2.5 and 60 mg l(-1), with peak levels during the bacillariophyceaen bloom and late clear water phase. The second phase did not appear to relate directly to changes in algal population, and may result from bacterial activity, algal lysis or zooplankton activity. As soluble EPS forms a major component of the total amount of dissolved carbon in lakes, the study of the soluble EPS is important to understand the carbon cycle in freshwaters. No direct correlation occurred between algal-associated mucilage and soluble EPS over a single annual cycle.

Tien CJ

Biosorption of metal ions by freshwater algae with different surface characteristics
PROCESS BIOCHEM 38 (4): 605-613 DEC 2 2002

Abstract:
Four freshwater algae with different cell surface characteristic, Oscillatoria limnetica, Anabaena spiroides, Eudorina elegans and Chlorella vulgaris, were chosen to examine their copper(II), cadmium(II) and lead(II) (copper, cadmium, and lead cations with a charge of 2+) sorption activity using the Freundlich model, in terms of the surface area/dry weight ratios, and the presence of other metal ions. Experimental data obeyed the Freundlich model, indicating multiple functional binding sites on algal surfaces. All four algae showed the highest sorption capacity for Pb among three metals. Their sorption activity varied with initial metal concentrations. The surface area/dry weight ratio was demonstrated to be a major parameter determining the sorption activities and mechanisms of algae. However, no apparent relationship occurred between metal-binding ability and, the presence and amount of mucilage. Competition of metal ions on algal surface binding sites was found differed with algal species and metal ions. The high and significantly different sorption activities for three metals by four algae suggested the suitability and good selectivity for treatment of different kinds of industrial effluents. (C) 2002 Elsevier Science Ltd. All rights reserved.