Identification of some main Streptococcus iniae associated proteins: relationship.

The surface-associated proteins play a key role in bacterial physiology and pathogenesis, and are the major targets in the development of new vaccines. These proteins contribute to the adaptation of bacteria to different hosts and environments. To study differences at the genomic level, we first sequenced the whole genome of Streptococcus iniae from fish (IUSA-1 strain) and compared it to Streptococcus iniae from human (9117 strain), revealing a high similitude between both strains. To gain further insights into host- and environment-specific differences, we then studied proteins in silico and by High Performance Liquid Chromatography. This approach successfully identified 54 secreted and surface proteins, including several proteins involved in cell wall synthesis and transport of solutes, as well as proteins with yet unknown function. These proteins highlight as interesting targets for further investigation in the interaction between Streptococcus iniae and its environment. Results reported in this study have shown a first analysis about the predicted and experimental associated proteins of Streptococcus iniae isolated from two different hosts: human and fish.

Whole-Genome Sequence of Serratia liquefaciens HUMV-21, a Cytotoxic, Quorum-Sensing, and Biofilm-Producing Clinical Isolate.

A clinical isolate of Serratia liquefaciens (strain HUMV-21) was obtained from a skin ulcer of an adult patient. We report here its complete genome assembly using PacBio single-molecule real-time (SMRT) sequencing, which resulted in a single circular chromosome with 5.3 Mb. About 5,844 protein-coding genes are predicted from this assembly.

Interactions of Streptococcus iniae with phagocytic cell line.

Streptococcus iniae has become one of the most serious aquatic pathogens in the last decade, causing large losses in wild and farmed fish worldwide. There is clear evidence that this pathogen is capable not only of causing serious disease in fish but also of being transferred to and infecting humans. In this study, we investigate the interaction of S. iniae with two murine macrophage cell lines, J774-A1 and RAW 264.7. Cytotoxicity assay demonstrated significant differences between live and UV-light killed IUSA-1 strains. The burst respiratory activity decreased to baseline after 1 and 4 h of exposure for J774-A1 and RAW 264.7, respectively. Immunofluorescent and ultrastructural study of infected cells confirmed the intracellular localization of bacteria at 1 h and 24 h post-infection. Using qRT-PCR arrays, we investigated the changes in the gene expression of immune relevant genes associated with macrophage activation. In this screening, we identified 11 of 84 genes up-regulated, we observed over-expression of pro-inflammatory response as IL-1α, IL-1ß, and TNF-α, without a good anti-inflammatory response. Present findings suggest a capacity of S. iniae to modulate a mammalian macrophages cell lines to their survival and replication intracellular, which makes this cell type as a reservoir for continued infection.

New aspects in the biology of Photobacterium damselae subsp. piscicida: pili, motility and adherence to solid surfaces.

We describe for the first time the presence of pilus-like structures on the surface of Photobacterium damselae subsp. piscicida (Phdp). The hint to this discovery was the ability of one strain to hemagglutinate human erythrocytes. Further analysis of several Phdp strains ultrastructure by electron microscopy revealed the presence of long, thin fibers, similar to pili of other Gram-negative bacteria. These appendages were also observed and photographed by scanning, transmission electron microscopy and immunofluorescence. Although this fish pathogen has been described as non-motile, all strains tested exhibit twitching motility, a flagella-independent type IV-dependent form of bacterial translocation over surfaces. As far as we are aware, the movement of Phdp bacteria on semi-solid or solid surfaces has not been described previously. Moreover, we speculate that Phdp twitching motility may be involved in biofilm formation. Microscopic examination of Phdp biofilms by microscopy revealed that Phdp biofilm architecture display extensive cellular chaining and also bacterial mortality during biofilm formation in vitro. Based on our results, standardized analyses of Phdp surface appendages, biofilms, motility and their impact on Phdp survival, ecology and pathobiology are now feasible.

Whole-Genome Sequence of the Fish Virulent Strain Streptococcus iniae IUSA-1, Isolated from Gilthead Sea Bream (Sparus aurata) and Red Porgy (Pagrus pagrus).

Streptococcus iniae is a major fish pathogen that produces invasive infections that result in economic losses in aquaculture. In this study, the draft genome sequence of Streptococcus iniae strain IUSA-1, isolated from a natural outbreak affecting gilthead sea bream (Sparus aurata) and red porgy (Pagrus pagrus), is presented.