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Ecological aspects of viruses in soils.

Williamson, Kurt Elliott.

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Ecological aspects of viruses in soils.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Ecological aspects of viruses in soils./
Author:	Williamson, Kurt Elliott.
Description:	174 p.
Notes:	Advisers: Karl E. Wommack; Mark Radosevich.
Contained By:	Dissertation Abstracts International67-12B.
Subject:	Agriculture, Soil Science. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3247690

Ecological aspects of viruses in soils.
Williamson, Kurt Elliott.

Ecological aspects of viruses in soils. - 174 p.

Advisers: Karl E. Wommack; Mark Radosevich.

Thesis (Ph.D.)--University of Delaware, 2007.

The importance of viruses in aquatic ecosystems has been established over the past decade. By contrast, the abundance and distribution of viruses in soils is almost completely unknown. An essential first step in any investigation of viruses in soil is evaluation of viral recovery methods suitable for subsequent cultivation-independent analyses. A comparison of four common elution buffers indicated that potassium citrate eluted the highest numbers of viruses from soils (1.5 X 108 gram dry weight-1 grand mean), but specific soil-eluant combinations posed significant problems to enumeration by epifluorescence microscopy. Thus, the measurement of phage abundance in soils varied with both the extraction methodology.Subjects--Topical Terms:

1017824
Agriculture, Soil Science.

Ecological aspects of viruses in soils.
LDR:04898nam 2200337 a 45 001 964279
005 20110901
008 110901s2007 eng d
035 $a (UMI)AAI3247690
035 $a AAI3247690
040 $a UMI $c UMI
100 1 $a Williamson, Kurt Elliott. $3 1287340
245 1 0 $a Ecological aspects of viruses in soils.
300 $a 174 p.
500 $a Advisers: Karl E. Wommack; Mark Radosevich.
500 $a Source: Dissertation Abstracts International, Volume: 67-12, Section: B, page: 6805.
502 $a Thesis (Ph.D.)--University of Delaware, 2007.
520 $a The importance of viruses in aquatic ecosystems has been established over the past decade. By contrast, the abundance and distribution of viruses in soils is almost completely unknown. An essential first step in any investigation of viruses in soil is evaluation of viral recovery methods suitable for subsequent cultivation-independent analyses. A comparison of four common elution buffers indicated that potassium citrate eluted the highest numbers of viruses from soils (1.5 X 108 gram dry weight-1 grand mean), but specific soil-eluant combinations posed significant problems to enumeration by epifluorescence microscopy. Thus, the measurement of phage abundance in soils varied with both the extraction methodology.
520 $a Triplicate sequential extractions of viruses from six Delaware soils indicated that initial extractions captured approximately 70% of total viral abundance across all soils. Thus, single extractions represent slight underestimations of natural viral abundance in these soils. More importantly, however, the results suggest that differences in abundance across sample sites appear to be biogeographical in nature, and are not simply artifact. In terms of diversity, extracted soil virus communities were dominated by bacteriophages with a wide range of capsid diameters and morphologies. Land form and management patterns were significantly correlated to both bacterial and viral abundance, as well as to soil organic matter and water content. Land management practices have also been shown to impact bacterial abundance and diversity. Collectively, these results suggest linkages between viral and bacterial communities in soils.
520 $a It has been proposed that lysogeny would be favored in soils, as this relationship provides for the long-term maintenance of viruses within host populations. However, little experimental data are available to support this. Induction assays were performed to test the prevalence of lysogenic bacterial hosts within soil bacterial communities. Thirty percent (6 of 20) of bacterial isolates from Delaware soil samples harbored mitomycin C (MC)-inducible prophages, while only one noninducible isolate spontaneously produced detectable quantities of phage particles. The magnitude of induction responses was dependent upon incubation conditions; removal of MC from the culture media after 30 minutes resulted in a marked increase in induction responses for three of the six lysogens. Furthermore, two of the isolates were polylysogens that produced more than one distinct type of phage particle, raising questions about the distribution of this phenotype among soil bacteria. These experiments suggest that lysogeny is common among cultivable soil bacteria. However, given the variability in induction responses, care should be taken in using induction assays as a measure of lysogeny within microbial communities.
520 $a Cultivation-independent induction assays were also developed to assess the prevalence of lysogenic bacteria in a variety of soil samples, including six from Antarctica, and four from Delaware. Induction experiments were carried out either by extracting bacteria from soil and subsequently exposing extracts to MC, or by exposing bacteria to MC through direct addition to soil slurries. The former extraction-induction approach generated significantly higher prophage induction than all other treatments and was highly reproducible. Although inducible fraction was higher in temperate Delaware soils than Antarctic soils, no clear correlations were found between lysogeny and soil physical properties. For the Delaware soil samples, the inducible fraction of extractable soil bacteria based on this cultivation-independent assay was comparable to the frequency of inducible lysogeny among cultivable isolates (approximately 30%). Collectively, these data indicate that lysogeny is common among soil bacteria, but the specific factors that promote lysogeny remain unclear.
590 $a School code: 0060.
650 4 $a Agriculture, Soil Science. $3 1017824
650 4 $a Biology, Ecology. $3 1017726
650 4 $a Biology, Microbiology. $3 1017734
650 4 $a Biology, Virology. $3 1019068
690 $a 0329
690 $a 0410
690 $a 0481
690 $a 0720
710 2 0 $a University of Delaware. $3 1017826
773 0 $t Dissertation Abstracts International $g 67-12B.
790 $a 0060
790 1 0 $a Radosevich, Mark, $e advisor
790 1 0 $a Wommack, Karl E., $e advisor
791 $a Ph.D.
792 $a 2007
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3247690