PubMed Health⌕ Search

Biomedical subjects

T Staley

Publications and source records attributed to T Staley.

4 recordsLinked to original sources
PubMed2002

Phylogenetic diversity of numerically important Arctic sea-ice bacteria cultured at subzero temperature.

Heterotrophic bacteria in sea ice play a key role in carbon cycling, but little is known about the predominant players at the phylogenetic level. In a study of both algal bands and clear ice habitats within summertime Arctic pack ice from the Chukchi Sea, we determined the abundance of total bacteria and actively respiring cells in melted ice samples using epifluorescence microscopy and the stains 4', 6'-diamidino-2-phenylindole 2HCl (DAPI) and 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), respectively. Organic-rich and -poor culturing media were used to determine culturable members by plating (at 0 degrees C and 5 degrees C) and most-probable-number (MPN) analyses (at -1 degrees C). Total bacterial counts ranged from 5.44 x 10(4) ml(-1) in clear ice to 2.41 x 10(6) ml(-1) in algal-band ice samples, with 2-27% metabolically active by CTC stain. Plating and MPN results revealed a high degree of culturability in both types of media, but greater success in oligotrophic media (to 62% of total abundance) and from clear ice samples. The bacterial enumeration anomaly, commonly held to mean <or= 0.01% cultured, was not demonstrated in any of our samples. Denaturing gradient gel electrophoresis was used to check the purity of 44 isolates and select representatives for subsequent sequencing. Phylogenetic analyses based on 16S rRNA sequences indicated close relationships exclusively to known marine psychrophiles within two bacterial divisions, Proteobacteria (in the genera Alteromonas, Colwellia, Glaciecola, Octadecabacter, Pseudoaltermonas and Shewanella) and Cytophaga-Flexibacter-Bacteroides (Cytophaga, Flavobacterium, Gelidibacter and Polaribacter). All cultures from the clear ice sample with highest (62%) culturability were closely related to each other or to psychrophilic Cytophaga-Flexibacter-Bacteroides (94.9-99.6% sequence similarities). Overall, these findings suggest limited, heterotrophic bacterial diversity at cold temperatures and may provide insight into the recent evolution of psychrophilic bacteria.

Arctic Regions↗
PubMed1997

Regulation of tie receptor expression on human endothelial cells by protein kinase C-mediated release of soluble tie.

The expression and activity of receptor tyrosine kinases (RTK) at the cell surface can be modulated by several different pathways including the proteolytic release of the extracellular domain as a soluble receptor. We investigated the regulation of tie receptor expression, an orphan RTK restricted to cells of hematopoietic and endothelial lineages, on primary human endothelial cells and a stably transfected Chinese hamster ovary (CHO) cell line. Tie was expressed in cells as a doublet of 135 and 125 kD; the 135-kD band represented mature cell surface receptor containing sialic acid and N-linked oligosaccharide residues, whereas the 125-kD band represented an intracellular pool of immature receptor. Phorbol 12-myristate 13-acetate (PMA) had dramatic effects on tie expression at the cell surface. Within 15 minutes of PMA treatment, the 135-kD band disappeared from the cell surface and was accompanied by the appearance of a 100-kD band in cell supernatants. The 100-kD band continued to accumulate in the media throughout the duration of PMA treatment during which mature tie receptor was undetectable on the cell surface by fluorescence-activated cell sorting (FACS) or in cell lysates by immunoblot analysis. Using specific antibodies, this 100-kD species was shown to be a soluble form of the tie receptor containing the extracellular domain. PMA-dependent release of soluble tie was mediated through the activation of protein kinase C (PKC); soluble tie was not released in the presence of PKC inhibitors, an inactive PMA analog, or following the downregulation of PKC through chronic PMA treatment. These results indicate that tie receptor expression on endothelial cells is regulated by the release of a soluble extracellular fragment following activation of PKC. Parallel pathways regulating c-kit, tumor necrosis factor (TNF), and colony-stimulating factor (CSF) receptor expression suggest that the release of extracellular receptor fragments represents an alternative mechanism through which cells modulate responses to growth factors and cytokines.

Animals↗