BackgroundMycoplasma hyopneumoniae, Mycoplasma flocculare and Mycoplasma hyorhinis live in swine respiratory tracts. M. flocculare, a commensal bacterium, is genetically closely related to M. hyopneumoniae, the causative agent of enzootic porcine pneumonia. M. hyorhinis is also pathogenic, causing polyserositis and arthritis. In this work, we present the genome sequences of M. flocculare and M. hyopneumoniae strain 7422, and we compare these genomes with the genomes of other M. hyoponeumoniae strain and to the a M. hyorhinis genome. These analyses were performed to identify possible characteristics that may help to explain the different behaviors of these species in swine respiratory tracts.ResultsThe overall genome organization of three species was analyzed, revealing that the ORF clusters (OCs) differ considerably and that inversions and rearrangements are common. Although M. flocculare and M. hyopneumoniae display a high degree of similarity with respect to the gene content, only some genomic regions display considerable synteny. Genes encoding proteins that may be involved in host-cell adhesion in M. hyopneumoniae and M. flocculare display differences in genomic structure and organization. Some genes encoding adhesins of the P97 family are absent in M. flocculare and some contain sequence differences or lack of domains that are considered to be important for adhesion to host cells. The phylogenetic relationship of the three species was confirmed by a phylogenomic approach. The set of genes involved in metabolism, especially in the uptake of precursors for nucleic acids synthesis and nucleotide metabolism, display some differences in copy number and the presence/absence in the three species.ConclusionsThe comparative analyses of three mycoplasma species that inhabit the swine respiratory tract facilitated the identification of some characteristics that may be related to their different behaviors. M. hyopneumoniae and M. flocculare display many differences that may help to explain why one species is pathogenic and the other is considered to be commensal. However, it was not possible to identify specific virulence determinant factors that could explain the differences in the pathogenicity of the analyzed species. The M. hyorhinis genome contains differences in some components involved in metabolism and evasion of the host’s immune system that may contribute to its growth aggressiveness. Several horizontal gene transfer events were identified. The phylogenomic analysis places M. hyopneumoniae, M. flocculare and M. hyorhinis in the hyopneumoniae clade.

BackgroundThe respiratory tract of swine is colonized by several bacteria among which are three Mycoplasma species: Mycoplasma flocculare, Mycoplasma hyopneumoniae and Mycoplasma hyorhinis. While colonization by M. flocculare is virtually asymptomatic, M. hyopneumoniae is the causative agent of enzootic pneumonia and M. hyorhinis is present in cases of pneumonia, polyserositis and arthritis. The genomic resemblance among these three Mycoplasma species combined with their different levels of pathogenicity is an indication that they have unknown mechanisms of virulence and differential expression, as for most mycoplasmas.MethodsIn this work, we performed whole-genome metabolic network reconstructions for these three mycoplasmas. Cultivation tests and metabolomic experiments through nuclear magnetic resonance spectroscopy (NMR) were also performed to acquire experimental data and further refine the models reconstructed in silico.ResultsEven though the refined models have similar metabolic capabilities, interesting differences include a wider range of carbohydrate uptake in M. hyorhinis, which in turn may also explain why this species is a widely contaminant in cell cultures. In addition, the myo-inositol catabolism is exclusive to M. hyopneumoniae and may be an important trait for virulence. However, the most important difference seems to be related to glycerol conversion to dihydroxyacetone-phosphate, which produces toxic hydrogen peroxide. This activity, missing only in M. flocculare, may be directly involved in cytotoxicity, as already described for two lung pathogenic mycoplasmas, namely Mycoplasma pneumoniae in human and Mycoplasma mycoides subsp. mycoides in ruminants. Metabolomic data suggest that even though these mycoplasmas are extremely similar in terms of genome and metabolism, distinct products and reaction rates may be the result of differential expression throughout the species.ConclusionsWe were able to infer from the reconstructed networks that the lack of pathogenicity of M. flocculare if compared to the highly pathogenic M. hyopneumoniae may be related to its incapacity to produce cytotoxic hydrogen peroxide. Moreover, the ability of M. hyorhinis to grow in diverse sites and even in different hosts may be a reflection of its enhanced and wider carbohydrate uptake. Altogether, the metabolic differences highlighted in silico and in vitro provide important insights to the different levels of pathogenicity observed in each of the studied species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2644-z) contains supplementary material, which is available to authorized users.

Mycoplasma hyopneumoniae is the etiologic agent of swine enzootic pneumonia. However other mycoplasma species and secondary bacteria are found as inhabitants of the swine respiratory tract, which can be also related to disease. In the present study we have performed a total DNA metagenomic analysis from the lungs of pigs kept in a field condition, with suggestive signals of enzootic pneumonia and without any infection signals to evaluate the bacteria variability of the lungs microbiota. Libraries from metagenomic DNA were prepared and sequenced using total DNA shotgun metagenomic pyrosequencing. The metagenomic distribution showed a great abundance of bacteria. The most common microbial families identified from pneumonic swine’s lungs were Mycoplasmataceae, Flavobacteriaceae and Pasteurellaceae, whereas in the carrier swine’s lungs the most common families were Mycoplasmataceae, Bradyrhizobiaceae and Flavobacteriaceae. Analysis of community composition in both samples confirmed the high prevalence of M. hyopneumoniae. Moreover, the carrier lungs had more diverse family population, which should be related to the lungs normal flora. In summary, we provide a wide view of the bacterial population from lungs with signals of enzootic pneumonia and lungs without signals of enzootic pneumonia in a field situation. These bacteria patterns provide information that may be important for the establishment of disease control measures and to give insights for further studies.

The swine respiratory ciliary epithelium is mainly colonized by Mycoplasma hyopneumoniae, Mycoplasma flocculare and Mycoplasma hyorhinis. While colonization by M. flocculare is virtually asymptomatic, M. hyopneumoniae and M. hyorhinis infections may cause respiratory disease. Information regarding transcript structure and gene abundance provides valuable insight into gene function and regulation, which has not yet been analyzed on a genome-wide scale in these Mycoplasma species. In this study, we report the construction of transcriptome maps for M. hyopneumoniae, M. flocculare and M. hyorhinis, which represent data for conducting comparative studies on the transcriptional repertory. For each species, three cDNA libraries were generated, yielding averages of 415,265, 695,313 and 93,578 reads for M. hyopneumoniae, M. flocculare and M. hyorhinis, respectively, with an average read length of 274 bp. The reads mapping showed that 92%, 98% and 96% of the predicted genes were transcribed in the M. hyopneumoniae, M. flocculare and M. hyorhinis genomes, respectively. Moreover, we showed that the majority of the genes are co-expressed, confirming the previously predicted transcription units. Finally, our data defined the RNA populations in detail, with the map transcript boundaries and transcription unit structures on a genome-wide scale.

Mycoplasma hyopneumoniae is associated with swine respiratory diseases. Although gene organization and regulation are well known in many prokaryotic organisms, knowledge on mycoplasma is limited. This study performed a comparative analysis of three strains of M. hyopneumoniae (7448, J and 232), with a focus on genome organization and gene comparison for open read frame (ORF) cluster (OC) identification. An in silico analysis of gene organization demonstrated 117 OCs and 34 single ORFs in M. hyopneumoniae 7448 and J, while 116 OCs and 36 single ORFs were identified in M. hyopneumoniae 232. Genomic comparison revealed high synteny and conservation of gene order between the OCs defined for 7448 and J strains as well as for 7448 and 232 strains. Twenty-one OCs were chosen and experimentally confirmed by reverse transcription–PCR from M. hyopneumoniae 7448 genome, validating our prediction. A subset of the ORFs within an OC could be independently transcribed due to the presence of internal promoters. Our results suggest that transcription occurs in ‘run-on’ from an upstream promoter in M. hyopneumoniae, thus forming large ORF clusters (from 2 to 29 ORFs in the same orientation) and indicating a complex transcriptional organization.

Fowl typhoid (FT) and pullorum disease (PD) are two important poultry infections caused by Salmonella enterica subsp. enterica serotype Gallinarum (S. Gallinarum). S. Gallinarum strains are adapted to birds and classified into biovars Gallinarum (bvGA) and Pullorum (bvPU) as they are the causative agent of FT and PD, respectively. In Brazil, FT/PD outbreaks have been reported along the last 50 years, but there was a recent increase of FT field reports with the suspicion it could be due to virulence reversion of the attenuated live vaccine SG9R. In this study, we applied molecular biology assays and phylogenetic methods to detect and investigate S. Gallinarum isolates from commercial poultry flocks in order to understand the evolutionary history and origin of the recent FT outbreaks in Brazil. S. Gallinarum isolates were obtained from thirteen different poultry flocks with clinical signs of FT/PD from 2013 to 2015. These isolates were serotyped, tested with three specific PCR (for the detection of bvGA, bvPU and live vaccine strain SG9R) and submitted to sequencing of a variable genome region (ISR analysis). The complete genome of one bvGA strain (BR_RS12) was also compared to other S. Gallinarum complete genomes (including other two Brazilian ones: bvGA 287/91 and bvPU FCVA198). PCR detected all thirteen isolates as S. Gallinarum (eight bvGA and five bvPU), none positive for SG9R strain. ISR analysis revealed that all eight bvGA isolates showed exactly the same nucleotide sequences with 100% similarity to reference strains, while two patterns were observed for bvPU. Genome phylogeny demonstrated distinct clades for bvGA and bvPU, with the bvGA clade showing a clear subdivision including three genomes: SG9R vaccine, the respective SG9 parent strain and one SG9R revertant field isolate (MB4523). The evolutionary rate of the total S. Gallinarum genome was calculated at 6.15×10 substitutions/site/year, with 2.8 observed substitutions per year per genome (1 SNP per 4292 bases). Phylodynamics analysis estimated that at least two introductions of S. Gallinarum bvGA happened in Brazil, the first in 1885 and the second in 1950. The Brazilian bvGA genomes 287/91 and BR_RS12 analyzed here were related to the early and the late introductions, respectively. In conclusion, these results indicate the occurrence of S. Gallinarum strains associated with FT outbreaks that have been circulating for more than 50 years in Brazil and are not originated from virulence reversion of the SG9R vaccine.

BackgroundThe species Azospirillum amazonense belongs to a well-known genus of plant growth-promoting bacteria. This bacterium is found in association with several crops of economic importance; however, there is a lack of information on its physiology. In this work, we present a comprehensive analysis of the genomic features of this species.ResultsGenes of A. amazonense related to nitrogen/carbon metabolism, energy production, phytohormone production, transport, quorum sensing, antibiotic resistance, chemotaxis/motility and bacteriophytochrome biosynthesis were identified. Noteworthy genes were the nitrogen fixation genes and the nitrilase gene, which could be directly implicated in plant growth promotion, and the carbon fixation genes, which had previously been poorly investigated in this genus. One important finding was that some A. amazonense genes, like the nitrogenase genes and RubisCO genes, were closer phylogenetically to Rhizobiales members than to species of its own order.ConclusionThe species A. amazonense presents a versatile repertoire of genes crucial for its plant-associated lifestyle.

Canine distemper virus (CDV) is a major dog pathogen belonging to the genus Morbillivirus of the family Paramyxoviridae. CDV causes disease and high mortality in dogs and wild carnivores. Although homologous recombination has been demonstrated in many members of Paramyxoviridae, these events have rarely been reported for CDV. To detect potential recombination events, the complete CDV genomes available in GenBank up to June 2015 were screened using distinct algorithms to detect genetic conversions and incongruent phylogenies. Eight putative recombinant viruses derived from different CDV genotypes and different hosts were detected. The breakpoints of the recombinant strains were primarily located on fusion and hemagglutinin glycoproteins. These results suggest that homologous recombination is a frequent phenomenon in morbillivirus populations under natural replication, and CDV vaccine strains might play an important role in shaping the evolution of this virus.