Biomineralization on the stalk of the eustigmatophyte Pseudocharaciopsis (Eustigmatophyceae)

Abstract

The stalks of the eustigmatophyte Pseudocharaciopsis minuta were examined by light and scanning electron microscopy. Light microscopy revealed orange-red granules at the base of the stalk. Energy dispersive X-ray microanalysis of the bases indicated that they were mainly composed of manganese. Manganese has not been previously reported from eustigmatophytes. This study indicates that the Eustigmatophyceae needs further study into many aspects of the biology. Characterization of mineralized structures is an important prerequisite to experimental studies on mechanisms of biomineralization in the algae. As the mineralization in Pseudocharaciopsis occurs extracellular, the composition of granules at the cell's none-living base provides an opportunity using energy dispersive X-ray elemental analysis system (EDS) to identify the type of metals present. Reported for the first time is the deposition of manganese on the stalk of Pseudocharaciopsis. MATERIALS AND METHODSPseudocharaciopsis minuta appeared in enrichment cultures containing Lagynion delicatulum, plant material, primarily Elodea canadensis from Lake Namunamu, North Island, New Zealand (39°53′ S, 175°28′ E), collected in February 1989. Unialgal cultures were established and maintained in Bold's 3N Bristol's medium with added soil water extract (BBM) (Starr and Zeikus 1987). Experimental cultures were grown in 10 × 100 mm plastic Petri dishes under long-day (16 : 8) photoperiods at 23°C; coolwhite fluorescent lamps yielded photons at 6-10 µmol This study supports the Eustigmatophyceae bear further investigation for the presence of metal elements in the remaining eight genera that produce mucilage but lack a stalk. As Santos (1996) points out, the chemical composition of the cell walls of the Eustigmatophyceae, and I can now add the mucilage, remain unclear. The presence of Mn on the stalks of Pseudocharaciopsis raises questions as to the possible functions of these stalks and Mn metabolism. ACKNOWLEDGEMENTS

Hydrocytium expands the phylogenetic, morphological, and genomic diversity of the poorly known green algal order Chaetopeltidales

“…Other chaetopeltidaleans ( Hormotilopsis , Floydiella , and Gormaniella ) have been originally described from terrestrial habitats (Trainor and Bold, 1953; Groover and Hofstetter, 1969; Robison et al, 2022). The extracellular deposits next to the attachment pad that we observed in H. acuminatum have been reported in other microalgae and shown, for example, to be mainly composed of manganese in a eustigmatophyte (Wujek, 2012).…”

Toward Modern Classification of Eustigmatophytes, Including the Description of Neomonodaceae Fam. Nov. and Three New Genera1

“…Substances from the surrounding medium may adhere to the stipe, causing it to become dark orange‐brown. In a morphologically similar yet not directly related eustigmatophyte Pseudocharaciopsis minuta , this coloration was shown to be due to the accumulation of metals such as Mn (Wujek ). Vegetative cells of Neomonodus (Fig.…”

Eustigmatophyceae

“…2a), probably composed of pectic materials with very little cellulose (Hibberd 1974). Biomineralization of manganese on the stalk surface was observed in Pseudocharaciopsis minuta (Wujek 2012).…”