Paenochrobactrum gallinarii gen. nov., sp. nov., isolated from air of a duck barn, and reclassification of Pseudochrobactrum glaciei as Paenochrobactrum glaciei comb. nov

Paenochrobactrum pullorum Bacteremia: A Case Report

Paenochrobactrum pullorum is a gram-negative bacterium and is not usually considered a human pathogen. This is the first case report of P. pullorum, highlighting the importance of understanding its clinical significance. The author reports a case of P. pullorum bacteremia from bilateral lower extremity wound infection.

Application of Whole Genome Sequencing and Pan-Family Multi-Locus Sequence Analysis to Characterize Relationships Within the Family Brucellaceae

The bacterial family Brucellaceae is currently composed of seven genera, including species of the genus Brucella, a number of which are significant veterinary and zoonotic pathogens. The bacteriological identification of pathogenic Brucella spp. may be hindered by their close phenotypic similarity to other members of the Brucellaceae, particularly of the genus Ochrobactrum. Additionally, a number of novel atypical Brucella taxa have recently been identified, which exhibit greater genetic diversity than observed within the previously described species, and which share genomic features with organisms outside of the genus. Furthermore, previous work has indicated that the genus Ochrobactrum is polyphyletic, raising further questions regarding the relationship between the genus Brucella and wider Brucellaceae. We have applied whole genome sequencing (WGS) and pan-family multi-locus sequence analysis (MLSA) approaches to a comprehensive panel of Brucellaceae type strains, in order to characterize relationships within the family. Phylogenies based on WGS core genome alignments were able to resolve phylogenetic relationships of 31 non-Brucella spp. type strains from within the family, alongside type strains of twelve Brucella species. A phylogeny based on concatenated pan-family MLSA data was largely consistent with WGS based analyses. Notably, recently described atypical Brucella isolates were consistently placed in a single clade with existing species, clearly distinct from all members of the genus Ochrobactrum and wider family. Both WGS and MLSA methods closely grouped Brucella spp. with a sub-set of Ochrobactrum species. However, results also confirmed that the genus Ochrobactrum is polyphyletic, with seven species forming a separate grouping. The pan-family MLSA scheme was subsequently applied to a panel of 50 field strains of the family Brucellaceae, isolated from a wide variety of sources. This analysis confirmed the utility of the pan-Brucellaceae MLSA scheme in placing field isolates in relation to recognized type strains. However, a significant number of these isolates did not cluster with currently identified type strains, suggesting the existence of additional taxonomic diversity within some members of the Brucellaceae. The WGS and pan-family MLSA approaches applied here provide valuable tools for resolving the identity and phylogenetic relationships of isolates from an expanding bacterial family containing a number of important pathogens.

Analysis of 1,000+ Type-Strain Genomes Substantially Improves Taxonomic Classification of Alphaproteobacteria

The class Alphaproteobacteria is comprised of a diverse assemblage of Gram-negative bacteria that includes organisms of varying morphologies, physiologies and habitat preferences many of which are of clinical and ecological importance. Alphaproteobacteria classification has proved to be difficult, not least when taxonomic decisions rested heavily on a limited number of phenotypic features and interpretation of poorly resolved 16S rRNA gene trees. Despite progress in recent years regarding the classification of bacteria assigned to the class, there remains a need to further clarify taxonomic relationships. Here, draft genome sequences of a collection of genomes of more than 1000 Alphaproteobacteria and outgroup type strains were used to infer phylogenetic trees from genome-scale data using the principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families and genera, including taxa recognized as problematic long ago but also quite recent taxa, as well as a few species were shown to be in need of revision. According proposals are made for the recognition of new orders, families and genera, as well as the transfer of a variety of species to other genera and of a variety of genera to other families. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which are confirmed as valuable taxonomic markers. Similarly, analysis of the gene content was shown to provide valuable taxonomic insights in the class. Significant incongruities between 16S rRNA gene and whole genome trees were not found in the class. The incongruities that became obvious when comparing the results of the present study with existing classifications appeared to be caused mainly by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. Another probable cause of misclassifications in the past is the partially low overall fit of phenotypic characters to the sequence-based tree. Even though a significant degree of phylogenetic conservation was detected in all characters investigated, the overall fit to the tree varied considerably.

Paenochrobactrum pullorum sp. nov. isolated from a chicken

A Gram-stain-negative, rod-shaped, oxidase-positive, non-spore-forming, non-motile bacterium (strain 280(T)) isolated from a chicken was studied for its taxonomic allocation. 16S rRNA gene sequence analyses clearly allocated the isolate in the genus Paenochrobactrum group with a 16S rRNA gene sequence similarity of 98.8% to the currently recognized species, Paenochrobactrum gallinarii and Paenochrobactrum glaciei. This allocation was confirmed by the fatty acid data (major fatty acids: C18:1ω7c and C19:0 cyclo ω8c) and a polyamine pattern with the major compound putrescine and relatively high amounts of spermidine. Also, the polar lipid profile with phosphatidylethanolamine, phosphatiylmonomethylethanolamine, phosphatidylglycerol, phosphatidylcholine and the genus-specific 'stretched aminolipid' was well in line with the description of the genus Paenochrobactrum. The quinone system consisted predominantly of ubiquinone Q-10 with traces of Q-9 and Q-11. DNA-DNA hybridization of strain 280T with Paenochrobactrum gallinarii Sa25T and Paenochrobactrum glaciei KMM 3858T showed relatedness values of 38.8% (reciprocal 20.2%) and 30.2% (reciprocal 29.8%), respectively. These results in combination with differentiating physiological and biochemical data clearly showed that strain 280T merits species status. We propose the name Paenochrobactrum pullorum sp. nov. to accommodate this strain with the type strain 280T (=LMG 28095T=CIP 110700T).

Falsochrobactrum ovis gen. nov., sp. nov., isolated from a sheep

A Gram-stain-negative, rod-shaped, oxidase-positive, non-spore-forming, non-motile bacterium (B1315(T)) was isolated from the placenta of a sheep with abortion. On the basis of 16S rRNA gene sequence analyses the strain was assigned to the Brucella-Ochrobactrum-Paenochrobactrum-Pseudochrobactrum group with 94.5-94.8 %, 94.3-96.1 %, 95.0-95.1 %, and 95.9-96.1 % sequence similarities to type strains of species of the four genera, respectively. Phylogenetic trees indicated a close relationship to the type strains of Ochrobactrum gallinifaecis and Ochrobactrum oryzae (95.9 and 96.1 % sequence similarity, respectively). Chemotaxonomic data confirmed the allocation of strain B1315(T) to the family Brucellaceae (quinone system: ubiquinone Q-10 and major fatty acids: C18 : 1ω7c and C19 : 0 cyclo ω8c). The polar lipid profile contained the major lipids diphosphatidylglycerol, phosphatidylmonomethylethanolamine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine and the unidentified but unique phospholipid PL7. The polyamine pattern of strain B1315(T) contained the major polyamines spermidine and putrescine. On the basis of the 16S rRNA gene and recA sequence phylogeny and chemotaxonomic data strain B1315(T) was clearly different from the genera Brucella, Ochrobactrum, Paenochrobactrum and Pseudochrobactrum. On the basis of these data we propose the novel genus Falsochrobactrum gen. nov. with the type species Falsochrobactrum ovis sp. nov. with the type strain B1315(T) ( = CCM 8460(T) = LMG 27356(T.)) The taxonomic allocation of O. gallinifaecis, which grouped inconsistently together with strain B1315(T) on the basis of 16S rRNA gene sequence data, but shows the chemotaxonomic features of the genus Ochrobactrum, remains to be clarified.