HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Melasniemi, H. Articles by Hernesmaa, A. Search for Related Content PubMed PubMed Citation Articles by Melasniemi, H. Articles by Hernesmaa, A. Agricola Articles by Melasniemi, H. Articles by Hernesmaa, A.

Yeast spores seem to be involved in biological phosphate removal: a microscopic in situ case study

University of Helsinki, Department of Applied Chemistry and Microbiology, PO Box 56, FIN-00014 University of Helsinki, Finland¹
Helsinki University of Technology, Laboratory of Environmental Engineering, PO Box 6100, FIN-02015 HUT, Finland²

Author for correspondence: Hannes Melasniemi. Tel: +358 9 4513845. Fax: +358 9 4513856. e-mail: hannes.melasniemi{at}hut.fi

The principal polyphosphate-accumulating organism (PAO) in a biological-phosphate-removal activated-sludge process was assessed microscopically. The organism was recognized by its distinct morphotype most easily after polyphosphate staining. The PAO occurred in large, homogeneous clusters. The cells of the PAO were the biggest cells abounding in the sludge – clearly bigger than average sludge bacteria. Typical of the principal PAO was a variation of cell size, even in fresh sludge. In acetate minimal medium containing ampicillin, the original principal PAO clusters were converted to clusters of clearly larger, polyphosphate-containing, vegetative yeast-like cells. Cycloheximide addition inhibited this and caused flock disintegration, disappearance of the principal PAO clusters and growth of free bacteria. The cell wall of the principal PAO was not of the usual bacterial character. It showed anomalous Gram staining, stained for chitin (not found in bacteria) and bound concanavalin A, like cell walls of many yeasts. In addition, the PAO cell wall was resistant to lysozyme, but sensitive to an enzyme mixture that lyses yeast cell walls. It was concluded that the principal PAO cells in the studied sludge were clustered spores of a yeast.

Keywords: biological-phosphate removal, polyphosphate, activated sludge, yeast spores

Abbreviations: BOD₇, seven-day biological oxygen demand; BPR, biological-phosphate removal; COD, chemical oxygen demand; DAPI, 4',6-diamidino-2-phenylindole; PAO, polyphosphate-accumulating organism; polyP, polyphosphate; UCT, University of Cape Town

^a Present address: University of Helsinki, Department of Biosciences, Division of General Microbiology, PO Box 56, FIN-00014 University of Helsinki, Finland