Cell surface hydrophobicity of Pseudomonas aeruginosa: Effects of monorhamnolipid and substrate on fatty acid and lipopolysaccharide content

Persistent Link:
http://hdl.handle.net/10150/282712
Title:
Cell surface hydrophobicity of Pseudomonas aeruginosa: Effects of monorhamnolipid and substrate on fatty acid and lipopolysaccharide content
Author:
Al-Tahhan, Ragheb Abdel-Razzak
Issue Date:
1998
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Cell surface hydrophobicity is a biosurfactant inducible parameter associated with increased biodegradation rates of hydrocarbons. Little is known about the types of physiological changes that are induced by a biosurfactant to change cell surface hydrophobicity. The objective of this study was to investigate the rhamnolipid-induced chemical and structural changes that cause the increase in cell surface hydrophobicity of two P. aeruginosa strains; P. aeruginosa ATCC 27853 and P. aeruginosa ATCC 9027. Both fatty acid and lipopolysaccharide content of cells were measured during growth on a soluble substrate; glucose, and a slightly soluble substrate; hexadecane in the presence and absence of monorhamnolipid. Cell surface hydrophobicity is a dynamic surface property that changes depending on strain, growth stage, substrate, and rhamnolipid addition. Results showed a general decline in the readily extractable lipid content that was correlated with increase in cell surface hydrophobicity. This decline took place only when growing cultures was supplied with rhamnolipid. In addition, rhamnolipid treatment caused a partial release of lipopolysaccharides (LPS) from the cells. This was indicated by KDO analysis and by SDS-PAGE analysis of LPS from culture supernatant. Also, LPS release from both strains was rhamnolipid concentration-dependent. Rates of LPS release from suspensions prepared from cells of both strains were highest at low rhamnolipid concentrations. Although increase in cell surface hydrophobicity was associated with LPS release, the amount of LPS released did not correlate with cell surface hydrophobicity. Rather the amount of LPS release was strain dependent. Cell surface ultrastructure revealed by scanning electron microscopy showed that the cells studied have a naturally rough surface. Cells grown in the presence of rhamnolipid had a smooth surface indicating a loss of the LPS from the outer membrane. Cells grown on hexadecane in the presence of rhamnolipid had deep pits on the cell surface which may act as hydrophobic sites that allow increased hexadecane absorption. These data suggest that biosurfactant addition caused LPS loss resulting in development of cell surface hydrophobicity.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, Ecology.; Biology, Microbiology.; Environmental Sciences.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Soil, Water and Environmental Sciences
Degree Grantor:
University of Arizona
Advisor:
Maier, Raina M.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleCell surface hydrophobicity of Pseudomonas aeruginosa: Effects of monorhamnolipid and substrate on fatty acid and lipopolysaccharide contenten_US
dc.creatorAl-Tahhan, Ragheb Abdel-Razzaken_US
dc.contributor.authorAl-Tahhan, Ragheb Abdel-Razzaken_US
dc.date.issued1998en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractCell surface hydrophobicity is a biosurfactant inducible parameter associated with increased biodegradation rates of hydrocarbons. Little is known about the types of physiological changes that are induced by a biosurfactant to change cell surface hydrophobicity. The objective of this study was to investigate the rhamnolipid-induced chemical and structural changes that cause the increase in cell surface hydrophobicity of two P. aeruginosa strains; P. aeruginosa ATCC 27853 and P. aeruginosa ATCC 9027. Both fatty acid and lipopolysaccharide content of cells were measured during growth on a soluble substrate; glucose, and a slightly soluble substrate; hexadecane in the presence and absence of monorhamnolipid. Cell surface hydrophobicity is a dynamic surface property that changes depending on strain, growth stage, substrate, and rhamnolipid addition. Results showed a general decline in the readily extractable lipid content that was correlated with increase in cell surface hydrophobicity. This decline took place only when growing cultures was supplied with rhamnolipid. In addition, rhamnolipid treatment caused a partial release of lipopolysaccharides (LPS) from the cells. This was indicated by KDO analysis and by SDS-PAGE analysis of LPS from culture supernatant. Also, LPS release from both strains was rhamnolipid concentration-dependent. Rates of LPS release from suspensions prepared from cells of both strains were highest at low rhamnolipid concentrations. Although increase in cell surface hydrophobicity was associated with LPS release, the amount of LPS released did not correlate with cell surface hydrophobicity. Rather the amount of LPS release was strain dependent. Cell surface ultrastructure revealed by scanning electron microscopy showed that the cells studied have a naturally rough surface. Cells grown in the presence of rhamnolipid had a smooth surface indicating a loss of the LPS from the outer membrane. Cells grown on hexadecane in the presence of rhamnolipid had deep pits on the cell surface which may act as hydrophobic sites that allow increased hexadecane absorption. These data suggest that biosurfactant addition caused LPS loss resulting in development of cell surface hydrophobicity.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, Ecology.en_US
dc.subjectBiology, Microbiology.en_US
dc.subjectEnvironmental Sciences.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineSoil, Water and Environmental Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMaier, Raina M.en_US
dc.identifier.proquest9901682en_US
dc.identifier.bibrecord.b38824826en_US
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