RESUMEN

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.

Asunto(s)

Aggregatibacter actinomycetemcomitans/metabolismo , Proteínas Bacterianas/metabolismo , Exotoxinas/metabolismo , Proteínas de la Membrana/metabolismo , Aggregatibacter actinomycetemcomitans/genética , Aggregatibacter actinomycetemcomitans/ultraestructura , Secuencia de Aminoácidos , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Membrana Celular/metabolismo , Membrana Celular/ultraestructura , Cromatografía Liquida , Electroforesis en Gel de Poliacrilamida , Interacciones Hidrofóbicas e Hidrofílicas , Immunoblotting , Proteínas de la Membrana/química , Proteínas de la Membrana/genética , Microscopía Electrónica de Transmisión , Datos de Secuencia Molecular , Mutagénesis Insercional , Operón/genética , Regiones Promotoras Genéticas/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de Aminoácido , Espectrometría de Masa por Ionización de Electrospray