Virulence factors regulation by the quorum-sensing and Rsm systems in the marine strain Pseudomonas aeruginosa ID4365, a natural mutant in lasR.

Pseudomonas aeruginosa is an opportunistic human pathogen that is able to produce several virulence factors such as pyocyanin, rhamnolipids and elastase. In the clinical reference strain PAO1, synthesis of these virulence factors is regulated transcriptionally by quorum sensing (QS) and post-transcriptionally by the Rsm system. Herein, we investigated the role of these systems in the control of the pyocyanin, rhamnolipids and elastase production in the marine strain ID4365. We found that this strain carries a nonsense mutation in lasR that makes it a natural mutant in the Las QS system. However, its QS response is still functional with the Rhl system activating virulence factors synthesis. We found that the Rsm system affects virulence factors production, since overexpression of RsmA reduces pyocyanin production whereas RsmY overexpression increases its synthesis. Unexpectedly, and in contrast to the type strain PAO1, inactivation of rsmA increases pyocyanin but reduces elastase and rhamnolipids production by a reduction of RhlR levels. Thus, QS and Rsm systems are involved in regulating virulence factors production, but this regulation is different to the PAO1 strain even though their genomes are highly conserved. It is likely that these differences are related to the different ecological niches in which these strains lived.

A Next-Generation Approach to Calculate Source-Sink Dynamics in Marine Metapopulations.

In marine systems, adult populations confined to isolated habitat patches can be connected by larval dispersal. Source-sink theory provides effective tools to quantify the effect of specific habitat patches on the dynamics of connected populations. In this paper, we construct the next-generation matrix for a marine metapopulation and demonstrate how it can be used to calculate the source-sink dynamics of habitat patches. We investigate the effect of environmental variables on the source-sink dynamics and demonstrate how the next-generation matrix can provide useful biological insight into transient as well as asymptotic dynamics of the model.

Microfocus X-ray CT (microCT) Imaging of Actinia equina (Cnidaria), Harmothoe sp. (Annelida), and Xenoturbella japonica (Xenacoelomorpha).

Traditionally, biologists have had to rely on destructive methods such as sectioning in order to investigate the internal structures of opaque organisms. Non-destructive microfocus X-ray computed tomography (microCT) imaging has become a powerful and emerging protocol in biology, due to technological advancements in sample staining methods and innovations in microCT hardware, processing computers, and data analysis software. However, this protocol is not commonly used, as it is in the medical and industrial fields. One of the reasons for this limited use is the lack of a simple and comprehensible manual that covers all of the necessary steps: sample collection, fixation, staining, mounting, scanning, and data analyses. Another reason is the vast diversity of metazoans, particularly marine invertebrates. Because of marine invertebrates' diverse sizes, morphologies, and physiologies, it is crucial to adjust experimental conditions and hardware configurations at each step, depending on the sample. Here, microCT imaging methods are explained in detail using three phylogenetically diverse marine invertebrates: Actinia equina (Anthozoa, Cnidaria), Harmothoe sp. (Polychaeta, Annelida), and Xenoturbella japonica (Xenoturbellida, Xenacoelomorpha). Suggestions on performing microCT imaging on various animals are also provided.

Pathogenic Vibrio species isolated from estuarine environments (Ceará, Brazil) - antimicrobial resistance and virulence potential profiles

ABSTRACT Detection of virulent strains associated with aquatic environment is a current concern for the management and control of human and animal health. Thus, Vibrio diversity was investigated in four estuaries from state of Ceará (Pacoti, Choró, Pirangi and Jaguaribe) followed by antimicrobial susceptibility to different antimicrobials used in aquaculture and detection of main virulence factors to human health. Isolation and identification were performed on TCBS agar (selective medium) and dichotomous key based on biochemical characteristics, respectively. Nineteen strains of genus Vibrio were catalogued. Vibrio parahaemolyticus (Choró River) and V. alginolyticus (Pacoti River) were the most abundant species in the four estuaries. All strains were submitted to disk diffusion technique (15 antimicrobials were tested). Resistance was found to: penicillin (82%), ampicillin (54%), cephalotin (7%), aztreonan (1%), gentamicin, cefotaxime and ceftriaxone (0.5%). Five pathogenic strains were chosen to verification of virulence factors. Four estuaries showed a high abundance of species. High number of tested positive strains for virulence is concerning, since some of those strains are associated to human diseases, while others are known pathogens of aquatic organisms.

Pathogenic Vibrio species isolated from estuarine environments (Ceará, Brazil) - antimicrobial resistance and virulence potential profiles.

Detection of virulent strains associated with aquatic environment is a current concern for the management and control of human and animal health. Thus, Vibrio diversity was investigated in four estuaries from state of Ceará (Pacoti, Choró, Pirangi and Jaguaribe) followed by antimicrobial susceptibility to different antimicrobials used in aquaculture and detection of main virulence factors to human health. Isolation and identification were performed on TCBS agar (selective medium) and dichotomous key based on biochemical characteristics, respectively. Nineteen strains of genus Vibrio were catalogued. Vibrio parahaemolyticus (Choró River) and V. alginolyticus (Pacoti River) were the most abundant species in the four estuaries. All strains were submitted to disk diffusion technique (15 antimicrobials were tested). Resistance was found to: penicillin (82%), ampicillin (54%), cephalotin (7%), aztreonan (1%), gentamicin, cefotaxime and ceftriaxone (0.5%). Five pathogenic strains were chosen to verification of virulence factors. Four estuaries showed a high abundance of species. High number of tested positive strains for virulence is concerning, since some of those strains are associated to human diseases, while others are known pathogens of aquatic organisms.

Ecological fitness and virulence features of Vibrio parahaemolyticus in estuarine environments.

Vibrio parahaemolyticus is a commonly encountered and highly successful organism in marine ecosystems. It is a fast-growing, extremely versatile copiotroph that is active over a very broad range of conditions. It frequently occurs suspended in the water column (often attached to particles or zooplankton), and is a proficient colonist of submerged surfaces. This organism is an important pathogen of animals ranging from microcrustaceans to humans and is a causative agent of seafood-associated food poisoning. This review examines specific ecological adaptations of V. parahaemolyticus, including its broad tolerances to temperature and salinity, its utilization of a wide variety of organic carbon and energy sources, and its pervasive colonization of suspended and stationary materials that contribute to its success and ubiquity in temperate and tropical estuarine ecosystems. Several virulence-related features are examined, in particular the thermostable direct hemolysin (TDH), the TDH-related hemolysin (TRH), and the type 3 secretion system, and the possible importance of these features in V. parahaemolyticus pathogenicity is explored. The impact of new and much more effective PCR primers on V. parahaemolyticus detection and our views of virulent strain abundance are also described. It is clear that strains carrying the canonical virulence genes are far more common than previously thought, which opens questions regarding the role of these genes in pathogenesis. It is also clear that virulence is an evolving feature of V. parahaemolyticus and that novel combinations of virulence factors can lead to emergent virulence in which a strain that is markedly more pathogenic evolves and propagates to produce an outbreak. The effects of global climate change on the frequency of epidemic disease, the geographic distribution of outbreaks, and the human impacts of V. parahaemolyticus are increasing and this review provides information on why this ubiquitous human pathogen has increased its footprint and its significance so dramatically.

A "Shark Encounter": Delayed Primary Closure and Prophylactic Antibiotic Treatment of a Great White Shark Bite.

BACKGROUND: Shark bites are rare but sensational injuries that are covered in the lay press but are not well described in the medical literature. CASE REPORT: We present the case of a 50-year-old man who sustained two deep puncture wounds to his thigh from a great white shark in the waters surrounding Isla de Guadalupe off the coast of Baja California, Mexico, during a caged SCUBA dive. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: We discuss our strategy of closing the wounds in a delayed primary fashion 24 hours after injury, our antibiotic choices, and the patient's course and review marine pathogens and appropriate antibiotic coverage.

Pathogenic marine microbes influence the effects of climate change on a commercially important tropical bivalve.

There is growing evidence that climate change will increase the prevalence of toxic algae and harmful bacteria, which can accumulate in marine bivalves. However, we know little about any possible interactions between exposure to these microorganisms and the effects of climate change on bivalve health, or about how this may affect the bivalve toxin-pathogen load. In mesocosm experiments, mussels, Perna viridis, were subjected to simulated climate change (warming and/or hyposalinity) and exposed to harmful bacteria and/or toxin-producing dinoflagellates. We found significant interactions between climate change and these microbes on metabolic and/or immunobiological function and toxin-pathogen load in mussels. Surprisingly, however, these effects were virtually eliminated when mussels were exposed to both harmful microorganisms simultaneously. This study is the first to examine the effects of climate change on determining mussel toxin-pathogen load in an ecologically relevant, multi-trophic context. The results may have considerable implications for seafood safety.

Climate influence on Vibrio and associated human diseases during the past half-century in the coastal North Atlantic.

Climate change is having a dramatic impact on marine animal and plant communities but little is known of its influence on marine prokaryotes, which represent the largest living biomass in the world oceans and play a fundamental role in maintaining life on our planet. In this study, for the first time to our knowledge, experimental evidence is provided on the link between multidecadal climatic variability in the temperate North Atlantic and the presence and spread of an important group of marine prokaryotes, the vibrios, which are responsible for several infections in both humans and animals. Using archived formalin-preserved plankton samples collected by the Continuous Plankton Recorder survey over the past half-century (1958-2011), we assessed retrospectively the relative abundance of vibrios, including human pathogens, in nine areas of the North Atlantic and North Sea and showed correlation with climate and plankton changes. Generalized additive models revealed that long-term increase in Vibrio abundance is promoted by increasing sea surface temperatures (up to ∼1.5 °C over the past 54 y) and is positively correlated with the Northern Hemisphere Temperature (NHT) and Atlantic Multidecadal Oscillation (AMO) climatic indices (P < 0.001). Such increases are associated with an unprecedented occurrence of environmentally acquired Vibrio infections in the human population of Northern Europe and the Atlantic coast of the United States in recent years.

Structural insights on identification of potential lead compounds targeting WbpP in Vibrio vulnificus through structure-based approaches.

WbpP encoding UDP-GlcNAC C4 epimerase is responsible for the activation of virulence factor in marine pathogen Vibrio vulnificus (V. vulnificus) and it is linked to many aquatic diseases, thus making it a potential therapeutic target. There are few reported compounds that include several natural products and synthetic compounds targeting Vibrio sp, but specific inhibitor targeting WbpP are unavailable. Here, we performed structure-based virtual screening using chemical libraries such as Binding, TOSLab and Maybridge to identify small molecule inhibitors of WbpP with better drug-like properties. Deficient structural information forced to model the structure and the stable protein structure was obtained through 30 ns of MD simulations. Druggability regions are focused for new lead compounds and our screening protocol provides fast docking of entire small molecule library with screening criteria of ADME/Lipinski filter/Docking followed by re-docking of top hits using a method that incorporates both ligand and protein flexibility. Docking conformations of lead molecules interface displays strong H-bond interactions with the key residues Gly101, Ser102, Val195, Tyr165, Arg298, Val209, Ser142, Arg233 and Gln200. Subsequently, the top-ranking compounds were prioritized using the molecular dynamics simulation-based conformation and stability studies. Our study suggests that the proposed compounds may aid as a starting point for the rational design of novel therapeutic agents.

The quest for a unified view of bacterial land colonization.

Exploring molecular mechanisms underlying bacterial water-to-land transition represents a critical start toward a better understanding of the functioning and stability of the terrestrial ecosystems. Here, we perform comprehensive analyses based on a large variety of bacteria by integrating taxonomic, phylogenetic and metagenomic data, in the quest for a unified view that elucidates genomic, evolutionary and ecological dynamics of the marine progenitors in adapting to nonaquatic environments. We hypothesize that bacterial land colonization is dominated by a single-gene sweep, that is, the emergence of dnaE2 derived from an early duplication event of the primordial dnaE, followed by a series of niche-specific genomic adaptations, including GC content increase, intensive horizontal gene transfer and constant genome expansion. In addition, early bacterial radiation may be stimulated by an explosion of land-borne hosts (for example, plants and animals) after initial land colonization events.

The evolutionary phylogeny of the oomycete "fungi".

Molecular sequencing has helped resolve the phylogenetic relationships amongst the diverse groups of algal, fungal-like and protist organisms that constitute the Chromalveolate "superkingdom" clade. It is thought that the whole clade evolved from a photosynthetic ancestor and that there have been at least three independent plastid losses during their evolutionary history. The fungal-like oomycetes and hyphochytrids, together with the marine flagellates Pirsonia and Developayella, form part of the clade defined by Cavalier-Smith and Chao (2006) as the phylum "Pseudofungi", which is a sister to the photosynthetic chromistan algae (phylum Ochrophyta). Within the oomycetes, a number of predominantly marine holocarpic genera appear to diverge before the main "saprolegnian" and "peronosporalean" lines, into which all oomycetes had been traditionally placed. It is now clear that oomycetes have their evolutionary roots in the sea. The earliest diverging oomycete genera so far documented, Eurychasma and Haptoglossa, are both obligate parasites that show a high degree of complexity and sophistication in their host parasite interactions and infection structures. Key morphological and cytological features of the oomycetes will be reviewed in the context of our revised understanding of their likely phylogeny. Recent genomic studies have revealed a number of intriguing similarities in host-pathogen interactions between the oomycetes with their distant apicocomplexan cousins. Therefore, the earlier view that oomycetes evolved from the largely saprotrophic "saprolegnian line" is not supported and current evidence shows these organisms evolved from simple holocarpic marine parasites. Both the hyphal-like pattern of growth and the acquisition of oogamous sexual reproduction probably developed largely after the migration of these organisms from the sea to land.