Salmonella Fimbriae: What is the Clue to Their Hairdo?

Fimbriae are important virulence factors for Salmonella pathogenesis. They mediate adhesion to host cells (including plants), food, stainless steel and much more. The fimbrial systems are organised in gene clusters of four to fifteen genes that code for structural, assembly and regulatory proteins. There are three kinds of fimbriae depending on their mode of assembly. The chaperone/usher (CU) fimbriae use a dedicated chaperone and usher protein to coordinate the subunit biogenesis on the cell surface. The curli fimbriae are assembled by nucleation/precipitation pathway. The type IV fimbria assembly requires a transmembrane apparatus and ATP to energise the reaction. Several fimbriae are conserved among Salmonella serovars, while some are present in a limited set or only specific serovars. Expression and regulation of fimbrial genes are not well understood, and most Salmonella fimbriae are poorly expressed during in vitro culture, which further complicates research concerning their regulation and role during infection. However, Salmonella fim gene cluster, coding for type-1 fimbriae, was widely studied and presents its own set of regulators. Investigating fimbrial distribution, expression and regulation will further elucidate their roles in bacterial pathogenesis and host specificity. Furthermore, fimbriae are important for developing efficient diagnostic tests and antimicrobial strategies against Salmonella

Unusual duplication of the insulin-like receptor in the crustacean Daphnia pulex

Background: The insulin signaling pathway (ISP) has a key role in major physiological events like carbohydrate metabolism and growth regulation. The ISP has been well described in vertebrates and in a few invertebrate model organisms but remains largely unexplored in non-model invertebrates. This study is the first detailed genomic study of this pathway in a crustacean species, Daphnia pulex. Results: The Daphnia pulex draft genome sequence assembly was scanned for major components of the ISP with a special attention to the insulin-like receptor. Twenty three putative genes are reported. The pathway appears to be generally well conserved as genes found in other invertebrates are present. Major findings include a lower number of insulin-like peptides in Daphnia as compared to other invertebrates and the presence of multiple insulin-like receptors (InR), with four genes as opposed to a single one in other invertebrates. Genes encoding for the Dappu_InR are likely the result of three duplication events and bear some unusual features. Dappu_InR-4 has undergone extensive evolutionary divergence and lacks the conserved site of the catalytic domain of the receptor tyrosine kinase. Dappu_InR-1 has a large insert and lacks the transmembranal domain in the b-subunit. This domain is also absent in Dappu_InR-3. Dappu_InR-2 is characterized by the absence of the cystein-rich region. Real-time q-PCR confirmed the expression of all four receptors. EST analyses of cDNA libraries revealed that the four receptors were differently expressed under various conditions. Conclusions: Duplications of the insulin receptor genes might represent an important evolutionary innovation in Daphnia as they are known to exhibit extensive phenotypic plasticity in body size and in the size of defensive structures in response to predation

Anti-inflammatory properties of natural ingredients used in combinations on adjuvant induced arthritis in rats

Background: Rheumatoid arthritis has seen a significant increase in both incidence and prevalence and its treatments show limited efficiency due to their undesirable effects on patient health. Therefore, major interests lie in the development of treatments with drugs derived from plants or other natural sources with little adverse effects as an alternative to current treatments. Hypothesis/Purpose: The present study evaluates the therapeutic effects of glucosamine against rheumatoid arthritis in combination with hyaluronic acid, resin extract of Boswellia serrata or a bark extract of Salix alba on an animal model. We suggest that combinations with plants could improve the attenuation of arthritis symptoms and articular inflammation. Study design: We used Freund’s complete adjuvant on rats as models of rheumatoid arthritis. Individuals were separated into eight experimental groups: a control group without arthritis, one with arthritis and without treatment, and six other groups receiving a daily therapeutic treatment from days 14 to 29. Methods: Hind-paw thickness and arthritis scores were measured at days 0, 3, 6 and 9 post-induction, and then every day from days 12 to 29 with a digital caliper and a score system respectively. At the end of the treatment, the mRNA content of three pro-inflammatory cytokines from cartilage was measured using real-time PCR. The total antioxidant activity was evaluated with an Antioxidant Assay Kit. Results: Treatments with Boswellia serrata and Salix alba (Glu+Hyal A+Bosw, Glu+Bosw+Sal, Glu+Bosw and Glu+Hyal A+Sal) saw significant reductions in hind-paw thickness and arthritis scores at the end of the experiment when compared to the untreated group. Expression of pro-inflammatory gene IL 17A was also reduced, but only the Glu+Hyal A+Sal combination significantly decreased the expression of IL-1β and TNF-α. The total antioxidant activity in blood plasma significantly increased in groups treated with plant extracts. Conclusion: The addition of Boswellia serrata and/or Salix alba attenuates clinical signs of rheumatoid arthritis in Freund’s complete adjuvant-induced arthritis in rats likely due to both their anti-inflammatory and antioxidant properties

Life-history traits display strong associations to genome size in annelids

Genome size, known also as the C-value, has been proposed as an important determinant of life-history variation in numerous animal taxa. We assessed the relationships between genome size and fitness-related life-history traits in six species of interstitial marine annelids of the genus Ophryotrocha. Life-history traits and genome size data obtained from 18 additional annelid species were included in our analyses to have a broader phylogenetic scope. Unexpectedly, genome sizes assessed here by flow cytometry in four Ophryotrocha species were three times larger than previously reported values obtained using Feulgen densitometry. This has implications for the hypothesis that harsh interstitial habitats select for small genomes in meiofaunal annelids. Within the genus Ophryotrocha, significant and positive relationships were found between genome size and nucleus size, and between genome size, age at first egg mass deposition, body size and lifespan. These relationships held up in the broader phylogenetic comparison. Our study provides evidence for the important role played by genome size in the evolution of life-history traits in annelids. -- Keywords : C-value ; Flow cytometry ; Ophryotrocha ; Body size ; Developmental rate ; Lifespan

Extensive gene rearrangements in the mitogenomes of congeneric annelid species and insights on the evolutionary history of the genus Ophryotrocha

Background Annelids are one the most speciose and ecologically diverse groups of metazoans. Although a significant effort has been recently invested in sequencing genomes of a wide array of metazoans, many orders and families within the phylum Annelida are still represented by a single specimen of a single species. The genus of interstitial annelids Ophryotrocha (Dorvilleidae, Errantia, Annelida) is among these neglected groups, despite its extensive use as model organism in numerous studies on the evolution of life history, physiological and ecological traits. To compensate for the paucity of genomic information in this genus, we here obtained novel complete mitochondrial genomes of six Ophryotrocha species using next generation sequencing. In addition, we investigated the evolution of the reproductive mode in the Ophryotrocha genus using a phylogeny based on two mitochondrial markers (COXI and 16S rDNA) and one nuclear fragment (Histone H3). Results Surprisingly, gene order was not conserved among the six Ophryotrocha species investigated, and varied greatly as compared to those found in other annelid species within the class Errantia. The mitogenome phylogeny for the six Ophryotrocha species displayed a separation of gonochoric and hermaphroditic species. However, this separation was not observed in the phylogeny based on the COX1, 16S rDNA, and H3 genes. Parsimony and Bayesian ancestral trait reconstruction indicated that gonochorism was the most parsimonious ancestral reproductive mode in Ophryotrocha spp. Conclusions Our results highlight the remarkably high level of gene order variation among congeneric species, even in annelids. This encourages the need for additional mitogenome sequencing of annelid taxa in order to properly understand its mtDNA evolution, high biodiversity and phylogenetic relationships. -- Keywords : Molecular phylogeny ; Dorvilleidae ; Mitogenome ; Next generation sequencing ; Model species ; Reproductive mode

Age Dependent Dysfunction of Mitochondrial and ROS Metabolism Induced by Mitonuclear Mismatch

Mitochondrial and nuclear genomes have to coevolve to ensure the proper functioning of the different mitochondrial complexes that are assembled from peptides encoded by both genomes. Mismatch between these genomes is believed to be strongly selected against due to the consequent impairments of mitochondrial functions and induction of oxidative stress. Here, we used a Drosophila model harboring an incompatibility between a mitochondrial tRNAtyr and its nuclear-encoded mitochondrial tyrosine synthetase to assess the cellular mechanisms affected by this incompatibility and to test the relative contribution of mitonuclear interactions and aging on the expression of impaired phenotypes. Our results show that the mitochondrial tRNA mutation caused a decrease in mitochondrial oxygen consumption in the incompatible nuclear background but no effect with the compatible nuclear background. Mitochondrial DNA copy number increased in the incompatible genotype but that increase failed to rescue mitochondrial functions. The flies harboring mismatch between nuclear and mitochondrial genomes had almost three times the relative mtDNA copy number and fifty percent higher rate of hydrogen peroxide production compared to other genome combinations at 25 days of age. We also found that aging exacerbated the mitochondrial dysfunctions. Our results reveal the tight interactions linking mitonuclear mismatch to mitochondrial dysfunction, mitochondrial DNA regulation, ROS production and aging

Diversity in the Reproductive Modes of European Daphnia pulicaria Deviates from the Geographical Parthenogenesis

10 páginas, 5 figuras, 3 tablas.Background: Multiple transitions to obligate parthenogenesis have occurred in the Daphnia pulex complex in North America. These newly formed asexual lineages are differentially distributed being found predominantly at high latitudes. This conforms to the rule of geographical parthenogenesis postulating prevalence of asexuals at high latitudes and altitudes. While the reproductive mode of high-latitude populations is relatively well studied, little is known about the reproduction mode in high altitudes. This study aimed to assess the reproductive mode of Daphnia pulicaria, a species of the D. pulex complex, from high altitude lakes in Europe. Methodology/Principal Findings: Variation at eight microsatellite loci revealed that D. pulicaria from the High Tatra Mountains (HTM) had low genotype richness and showed excess of heterozygotes and significant deviations from Hardy- Weinberg expectations, and was thus congruent with reproduction by obligate parthenogenesis. By contrast, populations from the Pyrenees (Pyr) were generally in Hardy-Weinberg equilibrium and had higher genotypic richness, suggesting that they are cyclic parthenogens. Four lakes from lowland areas (LLaP) had populations with an uncertain or mixed breeding mode. All D. pulicaria had mtDNA ND5 haplotypes of the European D. pulicaria lineage. Pyr were distinct from LLaP and HTM at the ND5 gene. By contrast, HTM shared two haplotypes with LLaP and one with Pyr. Principal Coordinate Analysis of the microsatellite data revealed clear genetic differentiation into three groups. HTM isolates were intermediate to Pyr and LLaP, congruent with a hybrid origin. Conclusion/Significance: Inferred transitions to obligate parthenogenesis have occurred only in HTM, most likely as a result of hybridizations. In contrast to North American populations, these transitions do not appear to involve meiosis suppressor genes and have not been accompanied by polyploidy. The absence of obligate parthenogenesis in Pyr, an environment highly similar to the HTM, may be due to the lack of opportunities for hybridization.Peer reviewe

No sex for Daphnia in the Italian Alps...

This study aimed to determine the reproductive mode and clonal diversity patterns of Daphnia pulicaria from four lakes in the Italian Alps

Functional Analysis of the Chaperone-Usher Fimbrial Gene Clusters of Salmonella enterica serovar Typhi

The human-specific pathogen Salmonella enterica serovar Typhi causes typhoid, a major public health issue in developing countries. Several aspects of its pathogenesis are still poorly understood. S. Typhi possesses 14 fimbrial gene clusters including 12 chaperone-usher fimbriae (stg, sth, bcf, fim, saf, sef, sta, stb, stc, std, ste, and tcf). These fimbriae are weakly expressed in laboratory conditions and only a few are actually characterized. In this study, expression of all S. Typhi chaperone-usher fimbriae and their potential roles in pathogenesis such as interaction with host cells, motility, or biofilm formation were assessed. All S. Typhi fimbriae were better expressed in minimal broth. Each system was overexpressed and only the fimbrial gene clusters without pseudogenes demonstrated a putative major subunits of about 17 kDa on SDS-PAGE. Six of these (Fim, Saf, Sta, Stb, Std, and Tcf) also show extracellular structure by electron microscopy. The impact of fimbrial deletion in a wild-type strain or addition of each individual fimbrial system to an S. Typhi afimbrial strain were tested for interactions with host cells, biofilm formation and motility. Several fimbriae modified bacterial interactions with human cells (THP-1 and INT-407) and biofilm formation. However, only Fim fimbriae had a deleterious effect on motility when overexpressed. Overall, chaperone-usher fimbriae seem to be an important part of the balance between the different steps (motility, adhesion, host invasion and persistence) of S. Typhi pathogenesis