Gene discovery through genomic sequencing of Brucella abortus

Brucella abortus is the etiological agent of brucellosis, a disease that af fects bovines and human. We generated DNA random sequences from the genome of B. abortus strain 2308 in order to characterize molecular targets that m ight be useful for developing immunological or chemotherapeutic strategies against this pathogen. The partial sequencing of 1,899 clones allowed the i dentification of 1,199 genomic sequence surveys (GSSs) with high homology ( BLAST expect value < 10(-5)) to sequences deposited in the GenBank database s. Among them, 925 represent putative novel genes for the Brucella genus. O ut of 925 nonredundant GSSs, 470 were classified in 15 categories based on cellular function. Seven hundred GSSs showed no significant database matche s and remain available for Further studies In order to identify their funct ion, A high number of GSSs with homology to Agrobacterium tumefaciens and R hizobium meliloti proteins were observed, thus confirming their close phylo genetic relationship, Among them, several GSSs showed high similarity with genes related to nodule nitrogen fixation, synthesis of nod factors, nodula tion protein symbiotic plasmid, and nodule bacteroid differentiation. We ha ve also identified several B. abortus homologs of virulence and pathogenesi s genes from other pathogens, including a homolog to both the Shda gene fro m Salmonella enterica serovar Typhimurium and the AidA-1 gene from Escheric hia coli, Other GSSs displayed significant homologies to genes encoding com ponents of the type III and type IV secretion machineries, suggesting that Brucella might also have an active type III secretion machinery.