Project description:Background: Lactococcus garvieae is a bacterial pathogen that affects different animal species and human. Despite the widespread distribution and emerging clinical significance of L. garvieae in both veterinary and human medicine, there is almost a complete lack of knowledge about the genetic content of this microorganism. In the present study the genomic content of L. garvieae CECT 4531 was analyzed by bioinformatic tools and microarray-based comparative genomic hybridizations (CGH) experiments, using Lactococcus lactis subsp. lactis IL1403 and Streptococcus pneumoniae TIGR4 as reference microorganisms. Results: The combination and integration of in silico analyses and in vitro (CGH) experiments performed between the reference microorganisms allowed establishing an inter-species hybridization framework with a detection threshold based on the sequence similarity ≥70%. With this threshold value, 267 genes were identified as having an analogue in L. garvieae, most of which (n = 258) have been documented for the first time in this pathogen. Most of these genes are related to ribosomal, sugar metabolism or energy conversion systems. Some identified genes could be involved in the pathogenesis of L. garvieae infections. Conclusions: In this study a comparative analysis based on microarray interspecies hybridization and the use of bioinformatic tools were used for the first time to study the genetic content of L. garvieae CECT 4531. Towards this approach, we identified 267 potentially present genes in L. garvieae CECT 4531, some of which could be involved in the pathogenesis of L. garvieae infections, such as als or mycA. These results provide the first insight into the genome content of L. garvieae.
Project description:This report describes the morphological characterization and genome analysis of an induced prophage (PLg-TB25) from a dairy strain of Lactococcus garvieae. The phage belongs to the Siphoviridae family and its morphology is typical of other lactococcal phages. A general analysis of its genome did not reveal similarities with other lactococcal phage genomes, confirming its novelty. However, similarities were found between genes of its morphogenesis cluster and genes of Gram-positive bacteria, suggesting that this phage genome resulted from recombination events that took place in a heterogeneous microbial environment. An in silico search for other prophages in 16 L. garvieae genomes available in public databases, uncovered eight seemingly complete prophages in strains isolated from dairy and fish niches. Genome analyses of these prophages revealed three novel L. garvieae phages. The remaining prophages had homology to phages of Lactococcus lactis (P335 group) suggesting a close relationship between these lactococcal species. The similarity in GC content of L. garvieae prophages to the genomes of L. lactis phages further supports the hypothesis that these phages likely originated from the same ancestor.
Project description:Lactococcus garvieae junior synonym Enterococcus seriolicida) is an emerging zoonotic agent isolated from economically important fish (rainbow trout and yellowtail), from cattle, and from humans. Clindamycin susceptibility is the only phenotypic test which can differentiate L. garvieae from Lactococcus lactis, another emerging agent in humans. A PCR assay for the identification of L. garvieae was developed and resulted in an amplified fragment of 1,100 bp in size. The PCR assay was shown to be specific to L. garvieae. The PCR assay was positive for all the L. garvieae strains tested, which originated from three different continents (Asia, Australia, and Europe). The PCR assay was negative for the phenotypically similar L. lactis and for all the other fish pathogens tested, including Streptococcus iniae and Aeromonas salmonicida. The PCR assay was applied to plasma obtained from diseased animals and was found sensitive enough to detect bacteria from 1 microl of plasma. The PCR assay that was developed is the only practical test besides the clindamycin test which can specifically identify the zoonotic agent L. garvieae and which can differentiate it from L. lactis.
Project description:Lactococcus garvieae is a lactic acid bacterium found in raw-milk dairy products as well as a range of aquatic and terrestrial environments. The plasmids in L. garvieae have received little attention compared to those of dairy Lactococcus lactis, in which the genes carried by these extrachromosomal elements are considered of adaptive value. The present work reports the sequencing and analysis of the plasmid complement of L. garvieae IPLA 31405, a strain isolated from a traditional, Spanish, starter-free cheese made from raw-milk. It consists of pLG9 and pLG42, of 9,124 and 42,240 nucleotides, respectively. Based on sequence and structural homology in the putative origin of replication (ori) region, pLG9 and pLG42 are predicted to replicate via a theta mechanism. Real-time, quantitative PCR showed the number of copies per chromosome equivalent of pLG9 and pLG42 to be around two and five, respectively. Sequence analysis identified eight complete open reading frames (orfs) in pLG9 and 36 in pLG42; these were organized into functional modules or cassettes containing different numbers of genes. These modules were flanked by complete or interrupted insertion sequence (IS)-like elements. Among the modules of pLG42 was a gene cluster encoding specific components of a phosphoenolpyruvate-phosphotransferase (PEP-PTS) system, including a phospho-β-galacosidase. The cluster showed a complete nucleotide identity respect to that in plasmids of L. lactis. Loss of pLG42 showed this to be involved in lactose assimilation. In the same plasmid, an operon encoding a type I restriction/modification (R/M) system was also identified. The specificity of this R/M system might be broadened by different R/M specificity subunits detected in pLG9 and in the bacterial chromosome. However, challenges of L. garvieae IPLA 31405 against L. lactis phages proved that the R/M system was not involved in phage resistance. Together, these results support the hypothesis that, as in L. lactis, pLG42 contribute towards the adaptation of L. garvieae to the dairy environment.
Project description:Lactococcus garvieae is a fish pathogen and an emerging zoonotic opportunistic pathogen as well as a component of natural microbiota in dairy products. Here, we present the first report of a genome sequence of L. garvieae TB25, isolated from a dairy source, and that of L. garvieae LG9, isolated from rainbow trout.