Structural studies on a 1.5-MDa bacterial adhesin reveal its adhesive and cohesive properties in biofilm formation
Thesis (Ph.D, Biochemistry) -- Queen's University, 2015-09-24 17:32:48.353 Ice-binding proteins (IBPs) have long been known to help organisms resist freezing (antifreeze) or tolerate freezing (ice recrystallization inhibition). Discoveries made in my thesis research reveal a third function for...
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ftqueensuniv:oai:qspace.library.queensu.ca:1974/13683 2023-05-15T13:58:56+02:00 Structural studies on a 1.5-MDa bacterial adhesin reveal its adhesive and cohesive properties in biofilm formation Guo, Shuaiqi Davies, Peter L. Biochemistry 2015-09-24 17:32:48.353 http://hdl.handle.net/1974/13683 eng eng Canadian theses http://hdl.handle.net/1974/13683 Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada ProQuest PhD and Master's Theses International Dissemination Agreement Intellectual Property Guidelines at Queen's University Copying and Preserving Your Thesis This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. Adhesin Ice-Binding Protein thesis 2015 ftqueensuniv 2020-12-29T09:08:37Z Thesis (Ph.D, Biochemistry) -- Queen's University, 2015-09-24 17:32:48.353 Ice-binding proteins (IBPs) have long been known to help organisms resist freezing (antifreeze) or tolerate freezing (ice recrystallization inhibition). Discoveries made in my thesis research reveal a third function for an IBP, which is host adhesion to ice. The IBP found on the cell surface of an Antarctic Gram-negative bacterium, Marinomonas primoryensis, is part of an exceptionally large protein of 1.5 MDa. The highly motile M. primoryensis swims to ice and attaches to the surface to form bacterial clusters. We suggest that MpAFP facilitates the formation of bacterial communities or biofilms underneath lake or sea ice, where oxygen and nutrients are most abundant due to the photosynthetic activity of other microorganisms. MpAFP can be divided into five distinct regions. The N-terminal end (RI) attaches to the bacterial cell envelope, likely by binding to the cell wall peptidoglycan or other polysaccharides on the cell surface while spanning the outer membrane. Next are ~ 120 identical tandem repeats of a 104-aa Ig-like domain (RII) that makes up 90% of the protein. Region III, which contains a carbohydrate-binding domain, separates the highly repetitive region II (RII) from the moderately repetitive region IV (RIV). The 34-kDa RIV, which folds as a Ca2+- dependent β-solenoid, is the only ice-binding domain of MpAFP. At the C terminus RV also contains Ca2+-binding RTX repeats that may serve as the secretion sequence for the giant protein. Using a “dissect and build” approach I succeeded in piecing together >95% of the structure of MpAFP. With this knowledge, I was able to postulate a general mechanism by which RTX adhesins enable their hosts to form biofilms by using a combination of surface adhesion and cell cohesion. X-ray crystallography suggests tandem arrays of the Ig-like repeats (RII) attract and slide along each other in an antiparallel fashion until their sugar binding domains lock onto each other’s’ surface glycans. Thus MpAFP not only binds the bacteria to ice but can potentially link the bacteria together in clusters to increase the total number of adhesins binding the group to the underside of ice where the environment is most favourable for growth. Given that many bacteria produce adhesins similar to MpAFP, work described in this thesis can be extended to give insight into the formation and disruption of other bacterial biofilms, including those of human pathogens. PhD Thesis Antarc* Antarctic Sea ice Queen's University, Ontario: QSpace Antarctic |
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Open Polar |
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Queen's University, Ontario: QSpace |
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ftqueensuniv |
language |
English |
topic |
Adhesin Ice-Binding Protein |
spellingShingle |
Adhesin Ice-Binding Protein Guo, Shuaiqi Structural studies on a 1.5-MDa bacterial adhesin reveal its adhesive and cohesive properties in biofilm formation |
topic_facet |
Adhesin Ice-Binding Protein |
description |
Thesis (Ph.D, Biochemistry) -- Queen's University, 2015-09-24 17:32:48.353 Ice-binding proteins (IBPs) have long been known to help organisms resist freezing (antifreeze) or tolerate freezing (ice recrystallization inhibition). Discoveries made in my thesis research reveal a third function for an IBP, which is host adhesion to ice. The IBP found on the cell surface of an Antarctic Gram-negative bacterium, Marinomonas primoryensis, is part of an exceptionally large protein of 1.5 MDa. The highly motile M. primoryensis swims to ice and attaches to the surface to form bacterial clusters. We suggest that MpAFP facilitates the formation of bacterial communities or biofilms underneath lake or sea ice, where oxygen and nutrients are most abundant due to the photosynthetic activity of other microorganisms. MpAFP can be divided into five distinct regions. The N-terminal end (RI) attaches to the bacterial cell envelope, likely by binding to the cell wall peptidoglycan or other polysaccharides on the cell surface while spanning the outer membrane. Next are ~ 120 identical tandem repeats of a 104-aa Ig-like domain (RII) that makes up 90% of the protein. Region III, which contains a carbohydrate-binding domain, separates the highly repetitive region II (RII) from the moderately repetitive region IV (RIV). The 34-kDa RIV, which folds as a Ca2+- dependent β-solenoid, is the only ice-binding domain of MpAFP. At the C terminus RV also contains Ca2+-binding RTX repeats that may serve as the secretion sequence for the giant protein. Using a “dissect and build” approach I succeeded in piecing together >95% of the structure of MpAFP. With this knowledge, I was able to postulate a general mechanism by which RTX adhesins enable their hosts to form biofilms by using a combination of surface adhesion and cell cohesion. X-ray crystallography suggests tandem arrays of the Ig-like repeats (RII) attract and slide along each other in an antiparallel fashion until their sugar binding domains lock onto each other’s’ surface glycans. Thus MpAFP not only binds the bacteria to ice but can potentially link the bacteria together in clusters to increase the total number of adhesins binding the group to the underside of ice where the environment is most favourable for growth. Given that many bacteria produce adhesins similar to MpAFP, work described in this thesis can be extended to give insight into the formation and disruption of other bacterial biofilms, including those of human pathogens. PhD |
author2 |
Davies, Peter L. Biochemistry |
format |
Thesis |
author |
Guo, Shuaiqi |
author_facet |
Guo, Shuaiqi |
author_sort |
Guo, Shuaiqi |
title |
Structural studies on a 1.5-MDa bacterial adhesin reveal its adhesive and cohesive properties in biofilm formation |
title_short |
Structural studies on a 1.5-MDa bacterial adhesin reveal its adhesive and cohesive properties in biofilm formation |
title_full |
Structural studies on a 1.5-MDa bacterial adhesin reveal its adhesive and cohesive properties in biofilm formation |
title_fullStr |
Structural studies on a 1.5-MDa bacterial adhesin reveal its adhesive and cohesive properties in biofilm formation |
title_full_unstemmed |
Structural studies on a 1.5-MDa bacterial adhesin reveal its adhesive and cohesive properties in biofilm formation |
title_sort |
structural studies on a 1.5-mda bacterial adhesin reveal its adhesive and cohesive properties in biofilm formation |
publishDate |
2015 |
url |
http://hdl.handle.net/1974/13683 |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic Sea ice |
genre_facet |
Antarc* Antarctic Sea ice |
op_relation |
Canadian theses http://hdl.handle.net/1974/13683 |
op_rights |
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada ProQuest PhD and Master's Theses International Dissemination Agreement Intellectual Property Guidelines at Queen's University Copying and Preserving Your Thesis This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
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1766267310466662400 |