Sex pheromones and plasmid transfer in Enterococcus faecalis

Plasmid-free Enterococcus faecalis excrete peptides (sex pheromones) which specifically induce a mating response in strains harboring certain conjugative plasmids. The response is characterized by the synthesis of a “fuzzy” surface material, visible by electron microscopy, which is believed to facilitate the aggregation of donors and recipients. Transconjugants which receive a specific plasmid shut down the production of endogenous pheromone; however, they continue to produce pheromones specific for donors harboring different classes of plasmids. In this review, we summarize what is known about the biochemistry and genetics of this phenomenon. Some emphasis is given to the hemolysin plasmid pAD1 and the regulation of its conjugal transfer.     

Visualization of the target-membrane-inserted fusion protein of Semliki Forest virus by combined electron microscopy and crystallography

Semliki Forest virus enters cells by receptor-mediated endocytosis. The acidic environment of the endosome triggers a membrane fusion reaction that is mediated by the E1 glycoprotein. During fusion, E1 rearranges from an E1/E2 heterodimer to a highly stable, membrane-inserted E1 homotrimer (E1HT). In this study, we analyzed E1HT by a combination of electron cryomicroscopy, electron crystallography of negatively stained 2D crystals, and fitting of the available X-ray structure of the monomeric E1 ectodomain into the resulting 3D reconstruction. The visualized E1HT reveals that the ectodomain has reoriented vertically and inserted the distal tip of domain II into the lipid bilayer. Our data allow the visualization of a viral fusion protein inserted in its target membrane and demonstrate that insertion is a cooperative process, resulting in rings composed of five to six homotrimers.     

The Distribution of Isopoda in the Delaware Bay Region

The distributions of 24 marine and estuarine isopods have been reviewed. Lironeca ovalis, Aegathoa medialis, Olencira praegustator, and Probopyrus pandalicola were the only parasitic species found. Of the 20 free-living isopods, Asellus communis and Chiridotea almyra were the only fresh to brackish water species, and Chiridotea arenicola, C. stenops, Cirolana impressa, C. polita and Edotea montosa were the true marine species. The salinity range of Cyathura burbancki was extended and the range of Chiridotea stenops was extended northward while the ranges of Chiridotea nigrescens and C. arenicola were extended southward. The contribution of isopod distributions to the concept of a shallow water Transatlantic zoogeographic province is discussed.     

Maternal weight affects placental DNA methylation of genes involved in metabolic pathways in the common marmoset monkey (Callithrix jacchus)

Accumulating evidence suggests that dysregulation of placental DNA methylation (DNAm) is a mechanism linking maternal weight during pregnancy to metabolic programming outcomes. The common marmoset, Callithrix jaccus, is a platyrrhine primate species that has provided much insight into studies of the primate placenta, maternal condition, and metabolic programming, yet the relationships between maternal weight and placental DNAm are unknown. Here, we report genome-wide DNAm from term marmoset placentas using reduced representation bisulfite sequencing. We identified 74 genes whose DNAm pattern is associated with maternal weight during gestation. These genes are predominantly involved in energy metabolism and homeostasis, including the regulation of glycolytic and lipid metabolic processes pathways.     

Reassessment of the status of Lymantria albescens and Lymantria postalba (Lepidoptera: Erebidae: Lymantriinae) as distinct ‘Asian gypsy moth’ species,using both mitochondrial and nuclear sequence data

For regulatory purposes, the name ‘Asian gypsy moth’ refers to a group of closely related Asian Lymantria species and subspecies whose female moths display flight capability, a trait believed to confer enhanced invasiveness relative to the European gypsy moth, Lymantria dispar dispar, whose females are flightless. Lymantria albescens and Lymantria postalba are Asian gypsy moths occurring in the southern Ryukyu Islands and in the northern Ryukyu and adjacent Kyushu and Shikoku Islands of Japan, respectively. Although once considered subspecies of L. dispar, their status as distinct species, relative to the latter, is now well established. While postalba was subsequently considered a subspecies of L. albescens, largely on the basis of differences in forewing ground colour in males, both taxa were later given distinct species status by Pogue & Schaefer (2007) following their revision of the genus Lymantria. Here, we re-examined the validity of this revised status through the sequencing of a large portion of the mitochondrial genome (c. 60%) and multiple nuclear marker genes [elongation factor 1-alpha (Ef-1α), wingless (Wgl), internal transcribed spacer 2 (ITS-2), ribosomal protein S5 (RpS5)] in representative specimens of both taxa and other Lymantria species, including L. monacha, L. xylina, L. mathura and members of the L. dispar + L. umbrosa clade. A comparison of the number of substitutions in these genomic regions among the taxa we considered showed lower or equivalent variation between L. albescens and L. postalba compared with subspecies of L. dispar, for mitochondrial and nuclear sequences, respectively. This finding was reflected in the maximum likelihood trees generated independently for mitochondrial and nuclear data, where L. albescens and L. postalba formed, in both analyses, a short-branch sister clade basal to the L. dispar + L. umbrosa clade. We further sequenced three markers [cytochrome c oxydase 1 (COI), EF-1α, Wgl] in multiple L. albescens–L. postalba specimens collected along a south-to-north transect across the Ryukyu Arc and observed no clear distinction among the sampled specimens as a function of taxonomic designation. We conclude that L. albescens and L. postalba form a single species, with postalba representing a darker-winged morph along an apparent south-to-north wing colour cline. Accordingly, L. postalba is relegated to synonymy under L. albescens ( syn.n. ).     

Control of Enterococcus faecalis sex pheromone cAD1 elaboration: Effects of culture aeration and pAD1 plasmid-encoded determinants

Aeration of plasmid-free Enterococcus faecalis strains resulted in an 8- to 16-fold decrease in sex pheromone cAD1 activity in culture filtrates. Levels of two unrelated pheromones, cPD1 and cAM373, were unaffected by culture aeration. Aeration also resulted in a decrease in the expression of conjugative transfer functions observed in cells containing pAD1 traB mutations, verifying a link between traB function and pheromone “shutdown.” Tests with a series of pAD1 mini-plasmids indicated that the product of the traB gene was involved in, but not sufficient for, pheromone shutdown; the cooperation of one or more other gene products encoded within the pheromone response control region was required.     

Comparative pathogenesis of three human and zoonotic SARS-CoV strains in cynomolgus macaques

The severe acute respiratory syndrome (SARS) epidemic was characterized by increased pathogenicity in the elderly due to an early exacerbated innate host response. SARS-CoV is a zoonotic pathogen that entered the human population through an intermediate host like the palm civet. To prevent future introductions of zoonotic SARS-CoV strains and subsequent transmission into the human population, heterologous disease models are needed to test the efficacy of vaccines and therapeutics against both late human and zoonotic isolates. Here we show that both human and zoonotic SARS-CoV strains can infect cynomolgus macaques and resulted in radiological as well as histopathological changes similar to those seen in mild human cases. Viral replication was higher in animals infected with a late human phase isolate compared to a zoonotic isolate. While there were significant differences in the number of host genes differentially regulated during the host responses between the three SARS-CoV strains, the top pathways and functions were similar and only apparent early during infection with the majority of genes associated with interferon signaling pathways. This study characterizes critical disease models in the evaluation and licensure of therapeutic strategies against SARS-CoV for human use.     

Identification and characterization of genes encoding sex pheromone cAM373 activity in Enterococcus faecalis and Staphylococcus aureus

The sex pheromone cAM373 of Enterococcus faecalis and the related staph-cAM373 of Staphylococcus aureus were found to correspond to heptapeptides located within the C-termini of the signal sequences of putative prelipoproteins. The deduced mature forms of the lipoproteins share no detectable homology and presumably serve unrelated functions in the cells. The chromosomally encoded genetic determinants for production of the pheromones have been identified and designated camE (encoding cAM373) and camS (encoding staph-cAM373). Truncated and full-length clones of camE were generated in Escherichia coli, in which cAM373 activity was expressed. In E. faecalis, insertional inactivation in the middle of camE had no detectable phenotypic effects on the pheromone system. Establishment of an in frame translation stop codon within the signal sequence resulted in reduction of cAM373 activity to 3% of normal levels. The camS determinant has homologues in Staphylococcus epidermidis, Bacillus subtilis and Listeria monocytogenes; however, corresponding heptapeptides present within those sequences do not resemble staph-cAM373 closely. The particular significance of staph-cAM373 as a potential intergeneric inducer of transfer-proficient genetic elements is discussed.