Research on natural environments, over the last decade, is replete with
microbial diversity studies that used culture-independent approaches. The cloning
and sequencing of the 16S rRNA genes has been the driving force in the expansion
of awareness about the great diversity of previously undiscovered microorganisms.
Well-known uncultured groups of microorganisms are numerous, and half of the
known phylogenetic divisions of bacteria are not represented in any culture
collection. It is no longer assumed that cultures acquired from an environment
represent the dominant or physiologically important organisms from that
environment. A high throughput culturing (HTC) technique was developed in an
attempt to bring into culture some of these widespread and uncultured
microorganisms. Over the course of 3 years, 2,484 culturing attempts were
screened for microbial growth from sample collections off the coast of Oregon and
576 attempts from groundwater at McClellan Air Force Base (MAFB). However,
using the HTC approach up to 14% of the microorganisms counted by direct
microscopy were cultured. In contrast, less than 1% of the microorganisms from
natural environments that are observed under a microscope can be grown using
standard agar plating techniques. This newly developed technique was successful
at bringing into culture 11 previously uncultured or undescribed Proteobacteria.
Four were isolated from the marine environment including, members of the SAR11
clade (alpha subclass), OM43 (beta-subclass), SAR92 (gamma subclass), and
OM60/OM241 (gamma subclass). SAR11 was transiently cultured in this study
but was later successfully brought into culture using these HTC techniques by Mike
Rapp��. Eight were isolated from a trichioroethene (TCE) and cis-dichloroethene
(cis-DCE) contaminated aquifer, including members of the MHP14 clade (alpha
subclass), 4-Org1-14 dade (alpha subclass), Herbaspirillum/Oxalobacter clade
(beta subclass), HTCC333 (beta subclass), HTCC410 (beta subclass), PM1 clade
(beta subclass), Boom-7m-04 clade (beta subclass) and OM43 clade (beta
subclass). Culturing microorganisms is an important step towards understanding
their physiology and ecology, and in most cases is necessary for the formal
systematic description of a new species. For microorganisms of global
significance, such as the major uncultured bacterioplankton and soil microbiota,
obtaining cultures is a prerequisite for obtaining complete genome sequences and
understanding the relevance of these microorganisms to biogeochemical cycles. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/31852 |
| Date | 04 November 2002 |
| Creators | Connon, Stephanie A. |
| Contributors | Giovannoni, Stephen J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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