Dr. Karen A. Homer

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King's College London
Dental Institute
Microbiology
Lecturer

Mailing Address

Department of Microbiology
The Dental Institute, King's College London
Floor 17, Guy's Tower
Guy's Hospital
London, SE1 9RT
United Kingdom

Contact Information

Phone: (207) 188-7464
Fax: (207) 188-7466
karen.a.homer@kcl.ac.uk

Qualifications

Ph.D., University of Newcastle upon Tyne.
B.Sc., University of Kent at Canterbury, Biochemistry.

Expertise and Research Interests

My research interests focus on studies of bacterial utilisation of glycoproteins, the response of bacteria to changing environmental conditions and expression of surface proteins.


We are investigating the mechanisms by which Streptococcus oralis and Enterococcus faecalis degrade glycoproteins in order to obtain sugars for growth. Glycoproteins are found in abundance in the human host and we are trying to unravel ways in which bacterial degradation of these molecules may be an important factor in infection. These studies are currently being extended to Streptococcus pneumoniae (a close relative of S. oralis), an important human pathogen.


The response of streptococci and enterococci to changing environmental conditions is being examined using a proteomics-based approach, exploiting the increasing availability of genome sequence data. Most of these efforts are focused on examination of bacterial surface-associated proteins because many virulence determinants and potential vaccine candidates are found here. My research includes projects designed to examine the response of bacteria to acid stress, nutrient limitation and exposure to antibiotics. We are now beginning to study the role of post-translational modification of bacterial proteins in response to various stress conditions. The research team is using two-dimensional gel electrophoresis, MALDI mass spectrometry and liquid chromatography/tandem mass spectrometry to carry out these studies.

Other Expertise

Course organiser for Infectious Disease component of BDS course.
Teach Microbiology to second year BDS Students. Lead tutor for undergraduate Microbiology practical sessions.
Member of Dental Institute Postgraduate Research Committee.
Committee member of Cells and Cell Surfaces group of Society for General Microbiology.
Committee member of Oral Microbiology and Immunology Group.

Future Research

I have recently expanded our proteomics work to include studies of mammalian systems in collaboration with colleagues in the Dental Institute and Medical School. The Department now has installed a new, high resolution and high mass accuracy linear trap/FTICR mass spectrometer and this equipment will enable me to expand the breadth of our collaborative work. Ongoing studies include protein-protein interactions in a number of cell lines and post-translational proteolytic modification.

Keywords

COS Keywords:

Antibiotics, Bacterial Infections, Biochemistry, Clinical Research or Studies, Electrophoresis, Infectious Diseases or Agents, Liquid Chromatography, Mass Spectrometry, Microbial Processes, Microbiology, Molecular Microbiology, Oral Diseases, Proteomics.

Additional Terms:

Enterococcus, Glycoproteins, Streptococcus, Surface Proteins.

Memberships

American Society for Mass Spectrometry
American Society for Microbiology
Biochemical Society
Society for General Microbiology

Previous Positions

1989-1992, Postdoctoral Fellow, University of London, Dental Institute, Hunterian Dental Research Unit, London Hospital Medical College
1988-1989, Postdoctoral Fellow, Royal College of Surgeons, Dental Research Unit

Funding Received

  • The University of London Central Research Fund: Streptococcus pneumoniae enolase: the effect of post-translational modification on function, £5,380, 2005 to 2005.
  • British Society for Antimicrobial Chemotherapy: Antibiotic susceptibility and biocide induction of efflux pumps in Gram-negative pathogenic oral bacteria (PhD Studentship), £58,500, 2003 to 2006.
  • Guy's, King's and St. Thomas' Dental Institute Research Committee: Phosphorylation of Streptococcal proteins as a response to environmental stress (PhD Studentship), £45,000, 2002 to 2005.
  • Guy's and St. Thomas' Charitable Foundation: Binding of Staphylococcus aureus to mucins, £66,660, 2000 to 2001.
  • King's College London Equipment Committee: HPAEC fluorescence detector and HPLC columns, £11,903, 1997 to 1997.
  • British Heart Foundation: Platelet glycoprotein-mediated growth of bacteria associated with infective endocarditis, £99,922, 1997 to 2000.
  • British Heart Foundation: Modulation and utilisation of platelet glycoprotein antigens by Streptococcus oralis assocaited with infective endocarditis, £40,343, 1996 to 1997.
  • King's College London Equipment Committee: Bacterial cell harvesting equipment, £6,519, 1995 to 1995.
  • University of London Central Research Fund: Metabolism of unsaturated disaccharides from glycosaminoglycans by Streptococcus intermedius, £1,000, 1995 to 1995.
  • National Heart Research Trust: The influence of enzymes from bacteria associated with endocarditis on the surface antigens of activated platelets, £3,200, 1995 to 1995.
  • King's College London Equipment Committee: Dionex DX-500 HPAEC-PAD system, £40,000, 1994 to 1994.
  • British Heart Foundation: Growth and metabolism of viridans streptococcci isolated from endocarditis, £23,871, 1994 to 1994.
  • King's College School of Medicine and Dentistry Joint Resarch Committee: Sialic acid metabolism by pathogenic oral streptococci (PhD Studentship), £35,000, 1994 to 1997.

Publications

  • Beighton D, Brailsford SR, Gilbert SC, Clark DT, Rao S, Wilkins JC, Tarelli E, Homer KA, Intra-oral Acid Production Associated With Eating Whole Or Pulped Raw Fruits, Caries Research, 38(4), 341-9, Jul-Aug 2004 Abstract
  • Wilkins JC, Beighton D, Homer KA, Effect of Acidic pH on Expression of Surface-Associated Proteins of Streptococcus oralis, Applied and Environmental Microbiology, 69(9), 5290-6, September 2003 Abstract
  • Wilkins JC, Homer KA, Beighton D, Analysis of Streptococcus mutans proteins modulated by culture under acidic conditions, Applied and Environmental Microbiology, 68(5), 2382-90, May 2002 Abstract
  • Wilkins JC, Homer KA, Beighton D, Altered protein expression of Streptococcus oralis cultured at low pH revealed by two-dimensional gel electrophoresis, Applied and Environmental Microbiology, 67(8), 3396-405, August 2001 Abstract
  • Roberts G, Homer KA, Tarelli E, Philpott-Howard J, Devriese LA, Beighton D, Distribution of endo-beta-N-acetylglucosaminidase amongst enterococci, Journal of Medical Microbiology, 50(7), 620-6, July 2001 Abstract
  • Homer KA, Roberts G, Byers HL, Tarelli E, Whiley RA, Philpott-Howard J, Beighton D, Mannosidase production by viridans group streptococci, Journal of Clinical Microbiology, 39(3), 995-1001, March 2001 Abstract
  • Byers HL, Tarelli E, Homer KA, Beighton D, Isolation and characterisation of sialidase from a strain of Streptococcus oralis, Journal of Medical Microbiology, 49(3), 235-44, March 2000 Abstract
  • Roberts G, Tarelli E, Homer KA, Philpott-Howard J, Beighton D, Production of an endo-beta-N-acetylglucosaminidase activity mediates growth of Enterococcus faecalis on a high-mannose-type glycoprotein, Journal of Bacteriology, 182(4), 882-90, February 2000 Abstract
  • Byers HL, Tarelli E, Homer KA, Hambley H, Beighton D, Growth of Viridans streptococci on human serum alpha1-acid glycoprotein, Journal of Dental Research, 78(7), 1370-80, July 1999 Abstract
  • Byers HL, Homer KA, Tarelli E, Beighton D, N-acetylneuraminic acid transport by Streptococcus oralis strain AR3, Journal of Medical Microbiology, 48(4), 375-81, April 1999 Abstract
  • Tarelli E, Byers HL, Homer KA, Beighton D, Evidence for mannosidase activities in Streptococcus oralis when grown on glycoproteins as carbohydrate source, Carbohydrate Research, 312(3), 159-64, November 1998 Abstract
  • Byers HL, Homer KA, Beighton D, Sialic acid utilisation by viridans streptococci, Advances in Experimental Medicine and Biology, 418, 713-6, 1997 Abstract
  • Shain H, Homer KA, Aduse-Opoku J, Beighton D, A conserved region of a hyaluronidase gene from Streptococcus intermedius, Advances in Experimental Medicine and Biology, 418, 769-72, 1997 Abstract
  • Byers HL, Homer KA, Beighton D, Utilization of sialic acid by viridans streptococci, Journal of Dental Research, 75(8), 1564-71, August 1996 Abstract
  • Rafay AM, Homer KA, Beighton D, Effect of mucin and glucose on proteolytic and glycosidic activities of Streptococcus oralis, Journal of Medical Microbiology, 44(6), 409-17, June 1996 Abstract
  • Shain H, Homer KA, Beighton D, Degradation and utilisation of chondroitin sulphate by Streptococcus intermedius, Journal of Medical Microbiology, 44(5), 372-80, May 1996 Abstract
  • Shain H, Homer KA, Beighton D, Purification and properties of a novel glycosaminoglycan depolymerase from Streptococcus intermedius strain UNS 35, Journal of Medical Microbiology, 44(5), 381-9, May 1996 Abstract
  • Homer KA, Kelley S, Hawkes J, Beighton D, Grootveld MC, Metabolism of glycoprotein-derived sialic acid and N-acetylglucosamine by Streptococcus oralis, Microbiology (reading, England), 142 ( Pt 5), 1221-30, May 1996 Abstract
  • Beighton D, Homer KA, Bouvet A, Storey AR, Analysis of enzymatic activities for differentiation of two species of nutritionally variant streptococci, Streptococcus defectivus and Streptococcus adjacens, Journal of Clinical Microbiology, 33(6), 1584-7, June 1995 Abstract
  • Bradshaw DJ, Homer KA, Marsh PD, Beighton D, Metabolic cooperation in oral microbial communities during growth on mucin, Microbiology (reading, England), 140 ( Pt 12), 3407-12, December 1994 Abstract
  • Homer KA, Grootveld MC, Hawkes J, Naughton DP, Beighton D, Degradation of hyaluronate by Streptococcus intermedius strain UNS 35, Journal of Medical Microbiology, 41(6), 414-22, December 1994 Abstract
  • Homer KA, Whiley RA, Beighton D, Production of specific glycosidase activities by Streptococcus intermedius strain UNS35 grown in the presence of mucin, Journal of Medical Microbiology, 41(3), 184-90, September 1994 Abstract
  • Homer KA, Denbow L, Beighton D, Spectrophotometric method for the assay of glycosaminoglycans and glycosaminoglycan-depolymerizing enzymes, Analytical Biochemistry, 214(2), 435-41, November 1993 Abstract
  • Homer KA, Denbow L, Whiley RA, Beighton D, Chondroitin sulfate depolymerase and hyaluronidase activities of viridans streptococci determined by a sensitive spectrophotometric assay, Journal of Clinical Microbiology, 31(6), 1648-51, June 1993 Abstract
  • Homer KA, Patel R, Beighton D, Effects of N-acetylglucosamine on carbohydrate fermentation by Streptococcus mutans NCTC 10449 and Streptococcus sobrinus SL-1, Infection and Immunity, 61(1), 295-302, January 1993 Abstract
  • Homer KA, Manji F, Beighton D, Inhibition of peptidase and glycosidase activities of Porphyromonas gingivalis, Bacteroides intermedius and Treponema denticola by plant extracts, Journal of Clinical Periodontology, 19(5), 305-10, May 1992 Abstract
  • Radford JR, Homer KA, Naylor MN, Beighton D, Inhibition of human subgingival plaque protease activity by chlorhexidine, Archives of Oral Biology, 37(4), 245-8, April 1992 Abstract
  • Homer KA, Beighton D, Synergistic degradation of bovine serum albumin by mutans streptococci and other dental plaque bacteria, Fems Microbiology Letters, 69(3), 259-62, January 1992 Abstract
  • Beighton D, Decker J, Homer KA, Effects of chlorhexidine on proteolytic and glycosidic enzyme activities of dental plaque bacteria, Journal of Clinical Periodontology, 18(2), 85-9, February 1991 Abstract
  • Homer KA, Whiley RA, Beighton D, Proteolytic activity of oral streptococci, Fems Microbiology Letters, 55(3), 257-60, February 1990 Abstract
  • Homer KA, Manji F, Beighton D, Inhibition of protease activities of periodontopathic bacteria by extracts of plants used in Kenya as chewing sticks (mswaki), Archives of Oral Biology, 35(6), 421-4, 1990 Abstract

Profile Details

Last Updated: 1/15/2007

COS Expertise ID #518509
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