{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/96635"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/96635","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Effect of Surface Chemistry and Young's Modulus on the Surface Motility of the Bacterium Pseudomonas Aeruginosa","abstract":"This study demonstrates that the surface motility of the bacterium Pseudomonas aeruginosa is dependent on the surface chemistry of the underlying substrate. In particular, cells on hydrophobic polydimethylsiloxane (PDMS) have a speed that is on average 38% greater than on hydrophilic PDMS. These results were obtained using time-lapse microscopy of bacteria exposed to continuously flowing tryptic soy broth growth medium at 37 ⁰C. Not only are the mean speeds different, the distributions of speeds are also different: on the hydrophobic substrate, a smaller proportion of bacteria move by less than about one body-length (~3 µm) in 60 minutes. In addition, the surface chemistry affects the orientation of the cells: there is a greater fraction of \"walking\" bacteria on the hydrophobic surface. Sensitivity to the substrate surface chemistry occurs despite the presence of a complex mix of substances in the growth medium and offers hope that surface chemistry can be used to tune motility and the progression to biofilm formation. Additionally, the effect of reducing the near-surface Young's modulus of the PDMS from 7000 to 70 kPA is investigated. For the lower modulus material, there is an increase in the likelihood of a bacterium executing sudden, high angle turns. This is evident in images with a framerate of one frame per 0.22s. However, the impact of these turns is averaged out over longer times such that the mean speed over periods of more than about one minute is the same for bacteria on both the high and the low modulus materials. Consequently, except over very short time intervals, Young's modulus in the surface region is not effective as a means of modulating motile behavior.","abstract_html":"This study demonstrates that the surface motility of the bacterium Pseudomonas aeruginosa is dependent on the surface chemistry of the underlying substrate. In particular, cells on hydrophobic polydimethylsiloxane (PDMS) have a speed that is on average 38% greater than on hydrophilic PDMS. These results were obtained using time-lapse microscopy of bacteria exposed to continuously flowing tryptic soy broth growth medium at 37 ⁰C. Not only are the mean speeds different, the distributions of speeds are also different: on the hydrophobic substrate, a smaller proportion of bacteria move by less than about one body-length (~3 µm) in 60 minutes. In addition, the surface chemistry affects the orientation of the cells: there is a greater fraction of "walking" bacteria on the hydrophobic surface. Sensitivity to the substrate surface chemistry occurs despite the presence of a complex mix of substances in the growth medium and offers hope that surface chemistry can be used to tune motility and the progression to biofilm formation. Additionally, the effect of reducing the near-surface Young's modulus of the PDMS from 7000 to 70 kPA is investigated. For the lower modulus material, there is an increase in the likelihood of a bacterium executing sudden, high angle turns. This is evident in images with a framerate of one frame per 0.22s. However, the impact of these turns is averaged out over longer times such that the mean speed over periods of more than about one minute is the same for bacteria on both the high and the low modulus materials. Consequently, except over very short time intervals, Young's modulus in the surface region is not effective as a means of modulating motile behavior.","abstract_has_math":false,"creators":["Hittel, Jonathan Erwin"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Chemical Engineering","degree_department":"Chemical Engineering","school":null,"contributors":[],"advisors":[],"committee_chairs":["Ducker, William A."],"committee_members":["Goldstein, Aaron S.","Whittington, Abby R."],"year":2020,"date_issued":"2020-01-30","date_published":"2020-01-30","updated_at":"2026-07-22T22:19:15Z","subjects":["Biofilm","bacteria","Pseudomonas aeruginosa","surface chemistry","hydrophilicity","wettability","Young's modulus","stiffness"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:23989"],"render_values":[{"text":"vt_gsexam:23989","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/96635","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Ducker, William A."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Goldstein, Aaron S.","Whittington, Abby R."]},{"key":"dc:contributor.department","label":"Department","values":["Chemical Engineering"]},{"key":"dc:creator","label":"Author","values":["Hittel, Jonathan Erwin"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2020-01-31T09:00:39Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2020-01-31T09:00:39Z"]},{"key":"dc:date.issued","label":"Date","values":["2020-01-30"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Biofilm","bacteria","Pseudomonas aeruginosa","surface chemistry","hydrophilicity","wettability","Young's modulus","stiffness"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:23989"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/96635"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["This study demonstrates that the surface motility of the bacterium Pseudomonas aeruginosa is dependent on the surface chemistry of the underlying substrate. In particular, cells on hydrophobic polydimethylsiloxane (PDMS) have a speed that is on average 38% greater than on hydrophilic PDMS. These results were obtained using time-lapse microscopy of bacteria exposed to continuously flowing tryptic soy broth growth medium at 37 ⁰C. Not only are the mean speeds different, the distributions of speeds are also different: on the hydrophobic substrate, a smaller proportion of bacteria move by less than about one body-length (~3 µm) in 60 minutes. In addition, the surface chemistry affects the orientation of the cells: there is a greater fraction of \"walking\" bacteria on the hydrophobic surface. Sensitivity to the substrate surface chemistry occurs despite the presence of a complex mix of substances in the growth medium and offers hope that surface chemistry can be used to tune motility and the progression to biofilm formation. Additionally, the effect of reducing the near-surface Young's modulus of the PDMS from 7000 to 70 kPA is investigated. For the lower modulus material, there is an increase in the likelihood of a bacterium executing sudden, high angle turns. This is evident in images with a framerate of one frame per 0.22s. However, the impact of these turns is averaged out over longer times such that the mean speed over periods of more than about one minute is the same for bacteria on both the high and the low modulus materials. Consequently, except over very short time intervals, Young's modulus in the surface region is not effective as a means of modulating motile behavior."]},{"key":"dc:description.abstractgeneral","label":"General Abstract","values":["This study demonstrates that the ability of the bacterium Pseudomonas aeruginosa to move on a solid surface is dependent on the surface chemistry of the underlying substrate. In particular, cells on hydrophobic polydimethylsiloxane (PDMS) have a speed that is on average 38% greater than on hydrophilic PDMS. These results were obtained using time-lapse microscopy of bacteria exposed to continuously flowing growth medium at 37 ⁰C. Not only are the mean speeds different, the distributions of speeds are also different: on the hydrophobic substrate, a smaller proportion of bacteria move by less than about one body-length (~3 µm) in 60 minutes. In addition, the surface chemistry affects the orientation of the cells: there is a greater fraction of vertically-oriented bacteria on the hydrophobic surface. Additionally, the effect of reducing the stiffness of the PDMS from 7000 to 70 kPA is investigated. For the less stiff material, there is an increase in the likelihood of a bacterium executing sudden, high angle turns. This is evident in images with a framerate of one frame per 0.22s. However, the impact of these turns is averaged out over longer times such that the mean speed over periods of more than about one minute is the same for bacteria on both the high and the low stiffness materials. Consequently, except over very short time intervals, stiffness in the surface region is not effective as a means of changing patterns of surface-bound P. aeruginosa movement."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["Effect of Surface Chemistry and Young's Modulus on the Surface Motility of the Bacterium Pseudomonas Aeruginosa"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Ducker, William A."],"dc:contributor.committeemember":["Goldstein, Aaron S.","Whittington, Abby R."],"dc:contributor.department":["Chemical Engineering"],"dc:creator":["Hittel, Jonathan Erwin"],"dc:date.accessioned":["2020-01-31T09:00:39Z"],"dc:date.available":["2020-01-31T09:00:39Z"],"dc:date.issued":["2020-01-30"],"dc:description.abstract":["This study demonstrates that the surface motility of the bacterium Pseudomonas aeruginosa is dependent on the surface chemistry of the underlying substrate. In particular, cells on hydrophobic polydimethylsiloxane (PDMS) have a speed that is on average 38% greater than on hydrophilic PDMS. These results were obtained using time-lapse microscopy of bacteria exposed to continuously flowing tryptic soy broth growth medium at 37 ⁰C. Not only are the mean speeds different, the distributions of speeds are also different: on the hydrophobic substrate, a smaller proportion of bacteria move by less than about one body-length (~3 µm) in 60 minutes. In addition, the surface chemistry affects the orientation of the cells: there is a greater fraction of \"walking\" bacteria on the hydrophobic surface. Sensitivity to the substrate surface chemistry occurs despite the presence of a complex mix of substances in the growth medium and offers hope that surface chemistry can be used to tune motility and the progression to biofilm formation. Additionally, the effect of reducing the near-surface Young's modulus of the PDMS from 7000 to 70 kPA is investigated. For the lower modulus material, there is an increase in the likelihood of a bacterium executing sudden, high angle turns. This is evident in images with a framerate of one frame per 0.22s. However, the impact of these turns is averaged out over longer times such that the mean speed over periods of more than about one minute is the same for bacteria on both the high and the low modulus materials. Consequently, except over very short time intervals, Young's modulus in the surface region is not effective as a means of modulating motile behavior."],"dc:description.abstractgeneral":["This study demonstrates that the ability of the bacterium Pseudomonas aeruginosa to move on a solid surface is dependent on the surface chemistry of the underlying substrate. In particular, cells on hydrophobic polydimethylsiloxane (PDMS) have a speed that is on average 38% greater than on hydrophilic PDMS. These results were obtained using time-lapse microscopy of bacteria exposed to continuously flowing growth medium at 37 ⁰C. Not only are the mean speeds different, the distributions of speeds are also different: on the hydrophobic substrate, a smaller proportion of bacteria move by less than about one body-length (~3 µm) in 60 minutes. In addition, the surface chemistry affects the orientation of the cells: there is a greater fraction of vertically-oriented bacteria on the hydrophobic surface. Additionally, the effect of reducing the stiffness of the PDMS from 7000 to 70 kPA is investigated. For the less stiff material, there is an increase in the likelihood of a bacterium executing sudden, high angle turns. This is evident in images with a framerate of one frame per 0.22s. However, the impact of these turns is averaged out over longer times such that the mean speed over periods of more than about one minute is the same for bacteria on both the high and the low stiffness materials. Consequently, except over very short time intervals, stiffness in the surface region is not effective as a means of changing patterns of surface-bound P. aeruginosa movement."],"dc:description.degree":["Master of Science"],"dc:format.medium":["ETD"],"dc:identifier.other":["vt_gsexam:23989"],"dc:identifier.uri":["http://hdl.handle.net/10919/96635"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["Biofilm","bacteria","Pseudomonas aeruginosa","surface chemistry","hydrophilicity","wettability","Young's modulus","stiffness"],"dc:title":["Effect of Surface Chemistry and Young's Modulus on the Surface Motility of the Bacterium Pseudomonas Aeruginosa"],"dc:type":["Thesis"],"thesis:degree_discipline":["Chemical Engineering"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:15Z"}