Cobban Alec

No Thumbnail Available
Last Name
Cobban
First Name
Alec
ORCID

Filters

2014 - 2016 3
3
3
Reset filters

Settings

Search Results

Now showing 1 - 3 of 3
  • Article
    Protist community grazing on prokaryotic prey in deep ocean water masses
    (Public Library of Science, 2015-04-20) Rocke, Emma ; Pachiadaki, Maria G. ; Cobban, Alec ; Kujawinski, Elizabeth B. ; Edgcomb, Virginia P.
    Oceanic protist grazing at mesopelagic and bathypelagic depths, and their subsequent effects on trophic links between eukaryotes and prokaryotes, are not well constrained. Recent studies show evidence of higher than expected grazing activity by protists down to mesopelagic depths. This study provides the first exploration of protist grazing in the bathypelagic North Atlantic Deep Water (NADW). Grazing was measured throughout the water column at three stations in the South Atlantic using fluorescently-labeled prey analogues. Grazing in the deep Antarctic Intermediate water (AAIW) and NADW at all three stations removed 3.79% ± 1.72% to 31.14% ± 8.24% of the standing prokaryote stock. These results imply that protist grazing may be a significant source of labile organic carbon at certain meso- and bathypelagic depths.
  • Article
    Revisiting the pink-red pigmented basidiomycete mirror yeast of the phyllosphere
    (John Wiley & Sons, 2016-05-10) Cobban, Alec ; Edgcomb, Virginia P. ; Burgaud, Gaëtan ; Repeta, Daniel J. ; Leadbetter, Edward R.
    By taking advantage of the ballistoconidium-forming capabilities of members of the genus Sporobolomyces, we recovered ten isolates from deciduous tree leaves collected from Vermont and Washington, USA. Analysis of the small subunit ribosomal RNA gene and the D1/D2 domain of the large subunit ribosomal RNA gene indicate that all isolates are closely related. Further analysis of their physiological attributes shows that all were similarly pigmented yeasts capable of growth under aerobic and microaerophilic conditions, all were tolerant of repeated freezing and thawing, minimally tolerant to elevated temperature and desiccation, and capable of growth in liquid or on solid media containing pectin or galacturonic acid. The scientific literature on ballistoconidium-forming yeasts indicates that they are a polyphyletic group. Isolates of Sporobolomyces from two geographically separated sites show almost identical phenotypic and physiological characteristics and a monophyly with a broad group of differently named Sporobolomyces/Sporidiobolus species based on both small subunit ribosomal RNA (SSU rRNA) and D1/D2 domains of the LSU rRNA gene sequences.
  • Article
    Benthic protists and fungi of Mediterranean deep hypsersaline anoxic basin redoxcline sediments
    (Frontiers Media, 2014-11-12) Bernhard, Joan M. ; Kormas, Konstantinos Ar. ; Pachiadaki, Maria G. ; Rocke, Emma ; Beaudoin, David J. ; Morrison, Colin R. ; Visscher, Pieter T. ; Cobban, Alec ; Starczak, Victoria R. ; Edgcomb, Virginia P.
    Some of the most extreme marine habitats known are the Mediterranean deep hypersaline anoxic basins (DHABs; water depth ∼3500 m). Brines of DHABs are nearly saturated with salt, leading many to suspect they are uninhabitable for eukaryotes. While diverse bacterial and protistan communities are reported from some DHAB water-column haloclines and brines, the existence and activity of benthic DHAB protists have rarely been explored. Here, we report findings regarding protists and fungi recovered from sediments of three DHAB (Discovery, Urania, L’ Atalante) haloclines, and compare these to communities from sediments underlying normoxic waters of typical Mediterranean salinity. Halocline sediments, where the redoxcline impinges the seafloor, were studied from all three DHABs. Microscopic cell counts suggested that halocline sediments supported denser protist populations than those in adjacent control sediments. Pyrosequencing analysis based on ribosomal RNA detected eukaryotic ribotypes in the halocline sediments from each of the three DHABs, most of which were fungi. Sequences affiliated with Ustilaginomycotina Basidiomycota were the most abundant eukaryotic signatures detected. Benthic communities in these DHABs appeared to differ, as expected, due to differing brine chemistries. Microscopy indicated that only a low proportion of protists appeared to bear associated putative symbionts. In a considerable number of cases, when prokaryotes were associated with a protist, DAPI staining did not reveal presence of any nuclei, suggesting that at least some protists were carcasses inhabited by prokaryotic scavengers.