Comparative Genomics of Early-Diverging <italic toggle="yes">Brucella</italic> Strains Reveals a Novel Lipopolysaccharide Biosynthesis Pathway
Alice R. Wattam,
Thomas J. Inzana,
Kelly P. Williams,
Shrinivasrao P. Mane,
Maulik Shukla,
Nalvo F. Almeida,
Allan W. Dickerman,
Steven Mason,
Ignacio Moriyón,
David O’Callaghan,
Adrian M. Whatmore,
Bruno W. Sobral,
Rebekah V. Tiller,
Alex R. Hoffmaster,
Michael A. Frace,
Cristina De Castro,
Antonio Molinaro,
Stephen M. Boyle,
Barun K. De,
João C. Setubal
Affiliations
Alice R. Wattam
Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, USA
Thomas J. Inzana
Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia, USA
Kelly P. Williams
Sandia National Laboratories, Livermore, California, USA
Shrinivasrao P. Mane
Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, USA
Maulik Shukla
Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, USA
Nalvo F. Almeida
Faculdade de Computação, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil
Allan W. Dickerman
Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, USA
Steven Mason
Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, USA
Ignacio Moriyón
Instituto de Salud Tropical y Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad de Navarra, Edificio de Investigación, Universidad de Navarra, c/Irunlarrea, Pamplona, Spain
David O’Callaghan
INSERM U1047, UFR Médecine, Nîmes, France
Adrian M. Whatmore
Department of Bacteriology, Animal Health & Veterinary Laboratories Agency, Woodham Lane, Addlestone, United Kingdom
Bruno W. Sobral
Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, USA
Rebekah V. Tiller
Centers for Disease Control and Prevention, Atlanta, Georgia, USA
Alex R. Hoffmaster
Centers for Disease Control and Prevention, Atlanta, Georgia, USA
Michael A. Frace
Centers for Disease Control and Prevention, Atlanta, Georgia, USA
Cristina De Castro
Department of Chemical Sciences, Università di Napoli Federico II, Complesso Universitario Monte Santangelo, Naples, Italy
Antonio Molinaro
Department of Chemical Sciences, Università di Napoli Federico II, Complesso Universitario Monte Santangelo, Naples, Italy
Stephen M. Boyle
Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia, USA
Barun K. De
Centers for Disease Control and Prevention, Atlanta, Georgia, USA
João C. Setubal
Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, USA
ABSTRACT Brucella species are Gram-negative bacteria that infect mammals. Recently, two unusual strains (Brucella inopinata BO1T and B. inopinata-like BO2) have been isolated from human patients, and their similarity to some atypical brucellae isolated from Australian native rodent species was noted. Here we present a phylogenomic analysis of the draft genome sequences of BO1T and BO2 and of the Australian rodent strains 83-13 and NF2653 that shows that they form two groups well separated from the other sequenced Brucella spp. Several important differences were noted. Both BO1T and BO2 did not agglutinate significantly when live or inactivated cells were exposed to monospecific A and M antisera against O-side chain sugars composed of N-formyl-perosamine. While BO1T maintained the genes required to synthesize a typical Brucella O-antigen, BO2 lacked many of these genes but still produced a smooth LPS (lipopolysaccharide). Most missing genes were found in the wbk region involved in O-antigen synthesis in classic smooth Brucella spp. In their place, BO2 carries four genes that other bacteria use for making a rhamnose-based O-antigen. Electrophoretic, immunoblot, and chemical analyses showed that BO2 carries an antigenically different O-antigen made of repeating hexose-rich oligosaccharide units that made the LPS water-soluble, which contrasts with the homopolymeric O-antigen of other smooth brucellae that have a phenol-soluble LPS. The results demonstrate the existence of a group of early-diverging brucellae with traits that depart significantly from those of the Brucella species described thus far. IMPORTANCE This report examines differences between genomes from four new Brucella strains and those from the classic Brucella spp. Our results show that the four new strains are outliers with respect to the previously known Brucella strains and yet are part of the genus, forming two new clades. The analysis revealed important information about the evolution and survival mechanisms of Brucella species, helping reshape our knowledge of this important zoonotic pathogen. One discovery of special importance is that one of the strains, BO2, produces an O-antigen distinct from any that has been seen in any other Brucella isolates to date.