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Characterization of the murein hydro...

Cullin, Nyssa C.

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Characterization of the murein hydrolase lytF of Streptococcus sanguinis.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Characterization of the murein hydrolase lytF of Streptococcus sanguinis./
Author:	Cullin, Nyssa C.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2017,
Description:	141 p.
Notes:	Source: Dissertations Abstracts International, Volume: 79-08, Section: B.
Contained By:	Dissertations Abstracts International79-08B.
Subject:	Molecular biology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10267346
ISBN:	9780355500820

Characterization of the murein hydrolase lytF of Streptococcus sanguinis.
Cullin, Nyssa C.

Characterization of the murein hydrolase lytF of Streptococcus sanguinis. - Ann Arbor : ProQuest Dissertations & Theses, 2017 - 141 p.

Source: Dissertations Abstracts International, Volume: 79-08, Section: B.

Thesis (Ph.D.)--The University of Oklahoma Health Sciences Center, 2017.

This item must not be added to any third party search indexes.

Dental caries, or tooth decay, is a biofilm-associated disease that results from dysbiosis of the oral bacterial population and commonly affects both children and adults. The oral biofilm develops through both cooperative and competitive means between the numerous bacterial species. Early colonizers are generally associated with health and are known to play major roles in biofilm maintenance, both structurally and genetically. Extracellular DNA (eDNA) is released from bacteria within the biofilm. eDNA contributes physically by promoting cell-cell and cell-tooth aggregation, nutritionally by serving as a carbon and energy source, and genetically by transferring information to increase genetic diversity for survival. This dissertation focused on the oral commensal Streptococcus sanguinis, which is a highly abundant, naturally competent early colonizer. The competence pathway of S. sanguinis plays a major role in biofilm formation via the uptake and release of eDNA, but the mechanisms for eDNA release are largely unknown. It was hypothesized that LytF, a competence-associated, murein hydrolase in S.sanguinis, plays a role in eDNA release and biofilm development; thus, the objective of this dissertation was to investigate the regulation and activity of LytF. Using lytF mutant and complemented strains, the competence regulation of lytF and hydrolytic activities of its gene product were examined. While expression of competence related genes was not altered in the lytF mutant, transformation efficiency was decreased and bacterial chains became elongated. Zymogram analysis proved that LytF is indeed a murein hydrolase and is not species-specific with regard to its muralytic activity; it can also hydrolyze the peptidoglycan of other oral streptococci. Scanning electron microscopy showed that bacteria producing an excess of LytF presented with morphological abnormalities characterized by enlarged and engorged cells. Additionally, these bacteria showed a decrease in biofilm formation. When LytF was used as a treatment it was shown to induce the release of eDNA from S. sanguinis, S. gordonii, S. mutans, and S. oralis. Similar treatment conditions showed extreme morphological abnormalities in biofilms. In all, this dissertation presents evidence that LytF is a highly regulated murein hydrolase that plays a role in eDNA release, biofilm formation, and due to its overall conservation among other oral streptococci, a potentially significant role in oral biofilm ecology. The work described here demonstrates that proper regulation of this competence-controlled protein is essential to S. sanguinis biofilm development and furthers the need to understand how bacterial species maintain themselves to contribute to the overall health of the oral biofilm.

ISBN: 9780355500820Subjects--Topical Terms:

517296
Molecular biology.

Characterization of the murein hydrolase lytF of Streptococcus sanguinis.
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300 $a 141 p.
500 $a Source: Dissertations Abstracts International, Volume: 79-08, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
500 $a Advisor: Kreth, Jens;Dyer, David W.
502 $a Thesis (Ph.D.)--The University of Oklahoma Health Sciences Center, 2017.
506 $a This item must not be added to any third party search indexes.
506 $a This item must not be sold to any third party vendors.
520 $a Dental caries, or tooth decay, is a biofilm-associated disease that results from dysbiosis of the oral bacterial population and commonly affects both children and adults. The oral biofilm develops through both cooperative and competitive means between the numerous bacterial species. Early colonizers are generally associated with health and are known to play major roles in biofilm maintenance, both structurally and genetically. Extracellular DNA (eDNA) is released from bacteria within the biofilm. eDNA contributes physically by promoting cell-cell and cell-tooth aggregation, nutritionally by serving as a carbon and energy source, and genetically by transferring information to increase genetic diversity for survival. This dissertation focused on the oral commensal Streptococcus sanguinis, which is a highly abundant, naturally competent early colonizer. The competence pathway of S. sanguinis plays a major role in biofilm formation via the uptake and release of eDNA, but the mechanisms for eDNA release are largely unknown. It was hypothesized that LytF, a competence-associated, murein hydrolase in S.sanguinis, plays a role in eDNA release and biofilm development; thus, the objective of this dissertation was to investigate the regulation and activity of LytF. Using lytF mutant and complemented strains, the competence regulation of lytF and hydrolytic activities of its gene product were examined. While expression of competence related genes was not altered in the lytF mutant, transformation efficiency was decreased and bacterial chains became elongated. Zymogram analysis proved that LytF is indeed a murein hydrolase and is not species-specific with regard to its muralytic activity; it can also hydrolyze the peptidoglycan of other oral streptococci. Scanning electron microscopy showed that bacteria producing an excess of LytF presented with morphological abnormalities characterized by enlarged and engorged cells. Additionally, these bacteria showed a decrease in biofilm formation. When LytF was used as a treatment it was shown to induce the release of eDNA from S. sanguinis, S. gordonii, S. mutans, and S. oralis. Similar treatment conditions showed extreme morphological abnormalities in biofilms. In all, this dissertation presents evidence that LytF is a highly regulated murein hydrolase that plays a role in eDNA release, biofilm formation, and due to its overall conservation among other oral streptococci, a potentially significant role in oral biofilm ecology. The work described here demonstrates that proper regulation of this competence-controlled protein is essential to S. sanguinis biofilm development and furthers the need to understand how bacterial species maintain themselves to contribute to the overall health of the oral biofilm.
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650 4 $a Dentistry. $3 828971
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710 2 $a The University of Oklahoma Health Sciences Center. $b Microbiology and Immunology. $3 3434124
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