TL;DR: Using molecular biology techniques, a gene that encodes a 26-kDa protein that is in the periplasm of B. abortus and in transformed Escherichia coli might be of value as an antigen for serological diagnosis of brucellosis in different mammals.
Abstract: Brucella spp. are the causative agents of brucellosis in many different hosts, including humans. Most of the serological methods of diagnosis are based on the detection of antilipopolysaccharide antibodies, which makes the differentiation of vaccinated animals from infected animals difficult. By using molecular biology techniques, a gene that encodes a 26-kDa protein (BP26) was isolated from a Brucella abortus S19 genome lambda gt11 library. This protein is in the periplasm of B. abortus and in transformed Escherichia coli. It is exported to the periplasm via a preprotein of 29 kDa with a signal sequence of 28 amino acids. The nucleotide and amino acid sequences of this gene and protein did not show any similarity with those of previously sequenced genes. The use of this protein in Western blotting allowed the differentiation between vaccinated bovines from infected bovines and the detection of infected rams: on the other hand, sera from human patients with active brucellosis were positive, while sera from human patients with chronic brucellosis or without clinical signs were nonreactive. BP26 might be of value as an antigen for serological diagnosis of brucellosis in different mammals.
TL;DR: Three novel Gram-negative, non-fermenting aerobic bacilli isolated from human clinical samples represent a novel species within the genus OchRobactrum, for which the name Ochrobactrum pseudintermedium sp.
Abstract: Three novel Gram-negative, non-fermenting aerobic bacilli were isolated from human clinical samples. They shared more than 99.8 % of the 16S rRNA gene nucleotide positions. The strains were related to Ochrobactrum intermedium with about 97.48 % 16S rRNA gene sequence similarity. In 16S rRNA gene-, dnaK- and rpoB-based phylogenies, the strains were grouped in a lineage that was distinct from other Ochrobactrum species in the family Brucellaceae. Fatty acid composition, polar lipids, quinone system, DNA–DNA relatedness, genome organization, and physiological and biochemical data differentiated these isolates from recognized species of the genus Ochrobactrum. The three clinical strains therefore represent a novel species within the genus Ochrobactrum, for which the name Ochrobactrum pseudintermedium sp. nov., is proposed. The type strain is ADV31T (=CIP 109116T=DSM 17490T). The DNA G+C content of strain ADV31T was 54.5 mol%.
TL;DR: A phylogenomic approach using a set of 145 Brucellaceae genomes representative of the family diversity and more than 40 genomes of the order Rhizobiales to infer the taxonomic relationships between the family’s species revealed that Ochrobactrum spp.
Abstract: Deciphering the evolutionary history of pathogenic bacteria and their near neighbors may help to understand the genetic or ecological bases which led to their pathogenic behavior. The Brucellaceae family comprises zoonotic pathogenic species belonging to the genus Brucella as well as the environmental genus Ochrobactrum for which some species are considered as opportunistic pathogens. Here, we used a phylogenomic approach including a set of 145 Brucellaceae genomes representative of the family diversity and more than 40 genomes of the order Rhizobiales to infer the taxonomic relationships between the family’s species. Our results clarified some unresolved phylogenetic ambiguities, conducting to the exclusion of Mycoplana spp. out of the family Brucellaceae and the positioning of all Brucella spp. as a single genomic species within the current Ochrobactrum species diversity. Additional analyses also revealed that Ochrobactrum spp. separate into two clades, one comprising mostly environmental species while the other one includes the species considered as pathogens (Brucella spp.) or opportunistic pathogens (mainly O. anthropi, O. intermedium, and O. pseudintermedium). Finally, we show that O. intermedium is undergoing a beginning of genome reduction suggestive of an ongoing ecological niche specialization, and that some lineages of O. intermedium and O. anthropi may shift toward an adaption to the human host.