title: An ultrastructural study of Paraphysoderma sedebokerense (Blastocladiomycota), an epibiotic parasite of microalgae.
abstract: Successful algal cultivation for biofuel production is one path in the transition to a renewable energy economy. The green alga Scenedesmus dimorphus is a candidate for biofuel production, but is subject to parasitism and subsequent population crash when cultivated in open ponds. From an open pond cultivating S. dimorphus for biofuel production in New Mexico, USA, an amoeboid parasite was isolated, designated as isolate FD61, and its rDNA operon sequenced. A BLAST search for nuc 18S rDNA (18S) sequence similarity identified the parasite as Paraphysoderma sedebokerense (Blastocladiomycota). Here, we examine the ultrastructure of P. sedebokerense and compare it with that of a sister taxon, Physoderma maydis. The parasite has thin-walled vegetative sporangia and thick-walled resting sporangia. Our observations indicate that amoeboid swarmers are produced in the vegetative phase, while either amoeboid swarmers or zoospores are the product of meiosis in resting sporangia. Meiosis is confirmed by the presence of synaptonemal complexes in resting sporangia nuclei. Notably, P. sedebokerense has a Golgi apparatus with stacked cisternae, a feature reported for P. maydis, but which is absent in all other examined taxa in Blastocladiomycota. This report furthers our knowledge of the life cycle of P. sedebokerense.
authors.affiliation: Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA. Electronic address: letch006@ua.edu.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Letcher
authors.affiliation: Crop Protection Group, Sapphire Energy, Inc., Las Cruces, NM 88007, USA.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Lee
authors.affiliation: Crop Protection Group, Sapphire Energy, Inc., Las Cruces, NM 88007, USA.
authors.forename: Salvador
authors.initials: S
authors.lastname: Lopez
authors.affiliation: Crop Protection Group, Sapphire Energy, Inc., Las Cruces, NM 88007, USA.
authors.forename: Micheal
authors.initials: M
authors.lastname: Burnett
authors.affiliation: Crop Protection Group, Sapphire Energy, Inc., San Diego, CA 92121, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: McBride
authors.affiliation: Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA.
authors.forename: Martha J
authors.initials: MJ
authors.lastname: Powell
mesh_terms: D055133:Blastocladiomycota / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure*; D000460:Chlorophyta / Q000382:microbiology*; D016000:Cluster Analysis; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D015388:Organelles / Q000648:ultrastructure; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S
keywords: Amoeboid swarmer; Biofuel; Golgi apparatus; Life cycle; Synaptonemal complex; Zoospore