Lim Ee Lin

No Thumbnail Available
Last Name
Lim
First Name
Ee Lin
ORCID

Filters

1997 - 1999 1 2000 - 2004 1
1 1
2
Reset filters

Settings

Search Results

Now showing 1 - 2 of 2
  • Thesis
    New insights on the ecology of free-living heterotrophic nanoflagellates based on the use of molecular biological approaches
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1997-03) Lim, Ee Lin
    Nanoplanktonic protists comprise a diverse assemblage of flagellate species responsible for various trophic processes in marine and freshwater ecosystems. Current methods for identifying small protists do not readily permit identification and enumeration of nanoplanktonic flagellates in cultures or field samples. The aim of this study was to apply molecular biological techniques for identification and enumeration of nanoflagellate taxa in water samples. Restriction fragment length polymorphism (RFLP) analysis of small subunit ribosomal DNA (SSU rONA) amplified by the polymerase chain reaction (PCR) differentiated pure cultures of heterotrophic nanoflagellates according to established taxonomic classification at the generic and species level. In addition, RFLP analysis of amplified SSU rONA permitted discrimination of polymorphic forms among species of flagellates from the genus Paraphysomonas. A fluorescent in situ hybridization method that uses rRNA-targeted oligonucleotide probes for counting protists from cultures and environmental water samples was developed. Preserved cells were intensely labeled with multiple eukaryote-specific oligonucleotide probes end-labeled with biotin and detected by fluorescein (FITC)-avidin. This probe hybridization method gave estimates of nanoplankton abundances that were often more representative of natural abundances than estimates obtained by commonly employed fluorochrome stains. The geographical distribution and seasonal abundance of the cosmopolitan heterotrophic flagellate, Paraphysomonas imperforata was examined in coastal waters using species-specific oligonucleotide probes. P. imperforata was found to occur at extremely low abundances in coastal environments, constituting ≤1% of the TNAN. However, P. imperforata often dominated the nanoplankton (up to 98% of TNAN) when water samples were enriched with bacteria. P. imperforata appears to be an opportunistic species capable of growing rapidly to high abundances when prey are abundant. Water temperature, small differences in the absolute abundance of P. imperforata, and nanoplankton grazers appeared to play a role in determining P. imperforata dominance. Results from this study also suggest that enrichment cultivation or perhaps incubations in general can select for nanoflagellates such as P. imperforata that may not be representative of abundant oceanic species.
  • Article
    Diversity and dynamics of a North Atlantic coastal Vibrio community
    (American Society for Microbiology, 2004-07) Thompson, Janelle R. ; Randa, Mark A. ; Marcelino, Luisa A. ; Tomita-Mitchell, Aoy ; Lim, Ee Lin ; Polz, Martin F.
    Vibrios are ubiquitous marine bacteria that have long served as models for heterotrophic processes and have received renewed attention because of the discovery of increasing numbers of facultatively pathogenic strains. Because the occurrence of specific vibrios has frequently been linked to the temperature, salinity, and nutrient status of water, we hypothesized that seasonal changes in coastal water bodies lead to distinct vibrio communities and sought to characterize their level of differentiation. A novel technique was used to quantify shifts in 16S rRNA gene abundance in samples from Barnegat Bay, N.J., collected over a 15-month period. Quantitative PCR (QPCR) with primers specific for the genus Vibrio was combined with separation and quantification of amplicons by constant denaturant capillary electrophoresis (CDCE). Vibrio populations identified by QPCR-CDCE varied between summer and winter samples, suggesting distinct warm-water and year-round populations. Identification of the CDCE populations by cloning and sequencing of 16S rRNA genes from two summer and two winter samples confirmed this distinction. It further showed that CDCE populations corresponded in most cases to ~98% rRNA similarity groups and suggested that the abundance of these follows temperature trends. Phylogenetic comparison yielded closely related cultured and often pathogenic representatives for most sequences, and the temperature ranges of these isolates confirmed the trends seen in the environmental samples. Overall, this suggests that temperature is a good predictor of the occurrence of closely related vibrios but that considerable microdiversity of unknown significance coexists within this trend.