title: Membrane morphology and leukotoxin secretion are associated with a novel membrane protein of Aggregatibacter actinomycetemcomitans.
abstract: Gram-negative bacteria display either a flat or an irregular outer membrane. The periodontal pathogen Aggregatibacter (Actinobacillus) actinomycetemcomitans has an irregular outer membrane. We have identified a gene that is associated with the biogenesis of this morphology. The gene is part of a three-gene operon and codes for a 141-kDa protein designated morphogenesis protein C (MorC), which is conserved in several gram-negative bacteria including Haemophilus influenzae and Pasteurella multocida. Insertional inactivation of this gene resulted in the conversion of an irregularly shaped membrane to a flat membrane. Associated with this morphological change were the autoaggregation of the bacteria during planktonic growth and a concomitant increase in the surface hydrophobicity of the bacterium. The absence of MorC also resulted in the loss of the secretion of leukotoxin but not the ltxA transcription. Our findings suggest that MorC is critical for membrane morphology and leukotoxin secretion in A. actinomycetemcomitans.
authors.affiliation: Department of Microbiology and Molecular Genetics, Stafford Hall, University of Vermont, Burlington, VT 05405, USA.
authors.forename: Claude V
authors.initials: CV
authors.lastname: Gallant
authors.forename: Maja
authors.initials: M
authors.lastname: Sedic
authors.forename: Erin A
authors.initials: EA
authors.lastname: Chicoine
authors.forename: Teresa
authors.initials: T
authors.lastname: Ruiz
authors.forename: Keith P
authors.initials: KP
authors.lastname: Mintz
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002853:Chromatography, Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D005098:Exotoxins / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D015151:Immunoblotting; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009876:Operon / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D001426:Bacterial Proteins; D005098:Exotoxins; D008565:Membrane Proteins; C018579:leukotoxin