Native root-associated bacteria rescue a plant from a sudden-wilt disease that emerged during continuous cropping

Plants maintain microbial associations whose functions remain largely unknown. For the past 15 y, we have planted the annual postfire tobacco Nicotiana attenuata into an experimental field plot in the plant’s native habitat, and for the last 8 y the number of plants dying from a sudden wilt disease has increased, leading to crop failure. Inadvertently we had recapitulated the common agricultural dilemma of pathogen buildup associated with continuous cropping for this native plant. Plants suffered sudden tissue collapse and black roots, symptoms similar to a Fusarium–Alternaria disease complex, recently characterized in a nearby native population and developed into an in vitro pathosystem for N. attenuata. With this in vitro disease system, different protection strategies (fungicide and inoculations with native root-associated bacterial and fungal isolates), together with a biochar soil amendment, were tested further in the field. A field trial with more than 900 plants in two field plots revealed that inoculation with a mixture of native bacterial isolates significantly reduced disease incidence and mortality in the infected field plot without influencing growth, herbivore resistance, or 32 defense and signaling metabolites known to mediate resistance against native herbivores. Tests in a subsequent year revealed that a core consortium of five bacteria was essential for disease reduction. This consortium, but not individual members of the root-associated bacteria community which this plant normally recruits during germination from native seed banks, provides enduring resistance against fungal diseases, demonstrating that native plants develop opportunistic mutualisms with prokaryotes that solve context-dependent ecological problems.Eukaryotes maintain many complex relationships with the microbes they host, which can be so abundant and diverse that they frequently are considered a eukaryote’s second genome. The complex relationships mediated by microbial associates are being revealed rapidly, thanks to the advances in sequencing, microbial culturing techniques, and the reconstitution of associated microbial communities in gnotobiotic systems (1, 2), even if some of these putative functional roles may need to be evaluated more critically (3).When plants germinate from their seed banks, they typically acquire a selection of the diverse fungi and bacteria that exist in native soils, and a subset of this community becomes root-associated. The best characterized are the bacterial microbiomes of Arabidopsis thaliana. Approximately half of the bacterial community in the plant root is representative of the soil flora; the remainder is a conserved core consisting of a smaller number of bacterial lineages from three phyla: Actinobacteria, Proteobacteria, and Bacteroidetes (2, 4). Because these bacterial communities occur in nondiseased plants, they are thought to represent commensalistic or possibly mutualistic associations.Root-associated microbes could benefit plants in many ways, and a recent review (5) highlighted the parallel functional roles of the microbiomes of the human gut and those of plant roots. The best-characterized beneficial functions for plants are (i) the plant growth-promoting rhizobacteria (PGPR), which promote growth by a variety of direct and indirect means that include increasing nutrient availability, interfering with ethylene (ET) signaling, and preventing diseases (6), and (ii) the bacteria that elicit induced systemic resistance (ISR) (7) by activating jasmonic acid (JA) and ET signaling (8). PGPR and ISR have been studied in a variety of cultivated and model plants, usually with model microbes (5), but little is known about their ecological context or whether they increase the growth and fitness of native plants. Whether PGPR and ISR functions occur among the well-characterized root-associated bacterial communities of Arabidopsis, either collectively or individually, also remains unknown.The well-described agricultural phenomenon of disease-suppressive soils that harbor microbiomes that suppress particular soil-borne pathogens (9) illustrates the complexity of the dynamics involved. Native soils have a certain degree of pathogen-suppressive ability, frequently seen when a crop is grown continuously in a soil, suffers an outbreak of a disease, and subsequently becomes resistant to the disease (5). Perhaps the mechanisms involved are best understood in a root disease of wheat caused by Gaeumannomyces graminis var Tritici infections, known as “take-all” disease. After many years of continuous wheat cropping with several disease outbreaks, the disease suddenly wanes, apparently because of the build-up of antagonistic Pseudomonas spp. (9). Whether any of these interactions also occur in native plants remains unknown.Nicotiana attenuata, a native annual tobacco of North America, germinates from long-lived seed banks to grow in the immediate postfire environment (10). When N. attenuata seeds germinate from their seed banks, they acquire a root-associated microbiome from their native soils which has been characterized by pyrosequencing and culture-dependent approaches (11–14). The composition of the root-associated microbiome is not influenced by a plant’s ability to elicit JA signaling (14), but ET signaling, as mediated by the ability both to produce and to perceive ET, plays a decisive role in shaping the “immigration policy” for the root-associated microbiome (12). A certain Bacillus strain, B55, was isolated from the roots of an ET-insensitive N. attenuata plant (35S etr-1) and was able to rescue the impaired-growth and high-mortality phenotype of ET-insensitive plants under field conditions (15). Beneficial effects were attributed to B55’s ability to reduce sulfur and produce dimethyl disulfide, which N. attenuata uses to alleviate sulfur deficiencies. This rescue provided one of the first demonstrations that the soil bacteria recruited by plants during germination can form opportunistic mutualistic relationships with their host based on the host plant’s ecological context. Here we provide a second example that involves protection against a sudden wilt disease, which accumulated in a field plot after consecutive planting of N. attenuata seedlings.     

Gene-air pollution interaction and cardiovascular disease: a review

Genetic susceptibility is likely to play a role in response to air pollution. Hence, gene-environment interaction studies can be a tool for exploring the mechanisms and the importance of the pathway in the association between air pollution and a cardiovascular outcome.In this article, we present a systematic review of the studies that have examined gene-environment interactions in relation to the cardiovascular health effects of air pollutants.We identified 16 articles meeting our search criteria. Of these studies, most have focused on individual functional polymorphisms or individual candidate genes. Moreover, they were all based on 3 study populations that have been extensively investigated in relation to air pollution effects: the Normative Aging Study, Air Pollution and Inflammatory Response in Myocardial Infarction Survivors: Gene-Environment Interaction in a High Risk Group, and Multiethnic Study of Atherosclerosis.In conclusions, the studies differed substantially in both the cardiovascular outcomes examined and the polymorphisms examined, so there is little confirmation of results across cohorts. Gene-environment interaction studies can help explore the mechanisms and the potential pathway in the association between air pollution and a cardiovascular outcome; replication of findings and studies involving multiple cohorts would be needed to draw stronger conclusions.     

The role of empirical albendazole treatment in idiopathic hypereosinophilia – a case series

Hypereosinophilia is usually defined as a blood eosinophil count >1500/μL. A broad variety of conditions are associated with hypereosinophilia. The present report describes three cases of hypereosinophilia, in which a thorough history, physical examination, laboratory and imaging investigations were unable to detect any abnormalities. Albendazole was empirically administered in all three cases, with complete normalization of eosinophil counts thereafter. Empirical treatment with albendazole for patients presenting with hypereosinophilia should be strongly considered.     

Modeling huanglongbing transmission within a citrus tree

The citrus disease huanglongbing (HLB), associated with an uncultured bacterial pathogen, is threatening the citrus industry worldwide. A mathematical model of the transmission of HLB between its psyllid vector and citrus host has been developed to characterize the dynamics of the vector and disease development, focusing on the spread of the pathogen from flush to flush (a newly developing cluster of very young leaves on the expanding terminal end of a shoot) within a tree. This approach differs from that of prior models for vector-transmitted plant diseases where the entire plant is the unit of analysis. Dynamics of vector and host populations are simulated realistically as the flush population approaches complete infection. Model analysis indicates that vector activity is essential for initial infection but is not necessary for continued infection because infection can occur from flush to flush through internal movement in the tree. Flush production, within-tree spread, and latent period are the most important parameters influencing HLB development. The model shows that the effect of spraying of psyllids depends on time of initial spraying, frequency, and efficacy of the insecticides. Similarly, effects of removal of symptomatic flush depend on the frequency of removal and the time of initiation of this practice since the start of the epidemic. Within-tree resistance to spread, possibly affected by inherent or induced resistance, is a major factor affecting epidemic development, supporting the notion that alternate routes of transmission besides that by the vector can be important for epidemic development.     

Pasteurella species peritoneal dialysis-associated peritonitis: Household pets as a risk factor

BACKGROUND:

Pasteurella species are Gram-negative coccobacilli that are a part of the normal oropharyngeal flora of numerous domestic animals. They have been recognized as a rare but significant cause of peritonitis in patients undergoing peritoneal dialysis (PD). A consensus about management strategies for PD-associated peritonitis caused by Pasteurella species currently does not exist.

METHODS:

The microbiological database serving the Manitoba Renal Program was searched from 1997 to 2013 for cases of Pasteurella species PD-associated peritonitis, and charts were reviewed. PubMed was searched for case reports and data were abstracted.

RESULTS:

Seven new local cases and 30 previously reported cases were analyzed. This infection is clinically similar to other forms of PD peritonitis, with household pet exposure appearing to be the strongest risk factor. Cats are the most commonly implicated pet. Direct contact between the pet and the equipment was commonly reported (25 of 37 patients) but was not necessary for infection to develop. The mean duration of treatment was 15 days. Complication rates were low, with only 11% of patients requiring PD catheter removal. There was no mortality reported.

CONCLUSION:

Pasteurella species are a rare cause of PD-associated peritonitis that can be successfully treated with a two-week course of intraperitoneal antibiotics with a high likelihood of catheter salvage.     

Heme-assisted S-nitrosation of a proximal thiolate in a nitric oxide transport protein

Certain bloodsucking insects deliver nitric oxide (NO) while feeding, to induce vasodilation and inhibit blood coagulation. We have expressed, characterized, and determined the crystal structure of the Cimex lectularius (bedbug) nitrophorin, the protein responsible for NO storage and delivery, to understand how the insect successfully handles this reactive molecule. Surprisingly, NO binds not only to the ferric nitrophorin heme, but it can also be stored as an S-nitroso (SNO) conjugate of the proximal heme cysteine (Cys-60) when present at higher concentrations. EPR- and UV-visible spectroscopies, and a crystallographic structure determination to 1.75-A resolution, reveal SNO formation to proceed with reduction of the heme iron, yielding an Fe-NO complex. Stopped-flow kinetic measurements indicate that an ordered reaction mechanism takes place: initial NO binding occurs at the ferric heme and is followed by heme reduction, Cys-60 release from the heme iron, and SNO formation. Release of NO occurs through a reversal of these steps. These data provide, to our knowledge, the first view of reversible metal-assisted SNO formation in a protein and suggest a mechanism for its role in NO release from ferrous heme. This mechanism and Cimex nitrophorin structure are completely unlike those of the nitrophorins from Rhodnius prolixus, where NO protection is provided by a large conformational change that buries the heme nitrosyl complex, highlighting the remarkable evolution of proteins that assist insects in bloodfeeding.     

Evidence for erythrocyte-binding antigen 175 as a component of a ligand-blocking blood-stage malaria vaccine

The ligands that pathogens use to invade their target cells have often proven to be good targets for vaccine development. However, Plasmodium falciparum has redundant ligands that mediate invasion of erythrocytes. The first requirement for the development of a successful ligand-blocking malaria vaccine is the demonstration that antibodies induced to each ligand can block the erythrocyte invasion of parasites with polymorphic sequences. Because of P. falciparum's redundancy in erythrocyte invasion, each ligand needs to be studied under artificial conditions in which parasite invasion is restricted in its use of alternative pathways. Here we investigate the role of erythrocyte-binding antigen 175 (EBA-175), a parasite ligand that binds to sialic acid on glycophorin A, in the invasion of erythrocytes by 10 P. falciparum clones under conditions in which invasion is partially limited to the EBA-175-glycophorin A pathway, using chymotrypsin-treated erythrocytes. We show that the ability to invade erythrocytes for both sialic acid-independent and sialic acid-dependent pathways requires the EBA-175-glycophorin A pathway for erythrocyte invasion. Importantly, antibodies against region II of EBA-175 from the 3D7 clone blocked invasion of chymotrypsin-treated erythrocytes by >50% by all parasite clones studied, including those with multiple different mutations described in the literature. The one exception was FCR3, which had a similar sequence to 3D7 but only 30% inhibition of invasion of chymotrypsin-treated erythrocytes, indicating alternative pathways for invasion of chymotrypsin-treated erythrocytes. Our findings suggest that antibodies to region II of EBA-175, as one component of a ligand-blocking malaria vaccine, are largely unaffected by polymorphism in EBA-175.     

Origin and diversification of wings: Insights from a neopteran insect

Winged insects underwent an unparalleled evolutionary radiation, but mechanisms underlying the origin and diversification of wings in basal insects are sparsely known compared with more derived holometabolous insects. In the neopteran species Oncopeltus fasciatus, we manipulated wing specification genes and used RNA-seq to obtain both functional and genomic perspectives. Combined with previous studies, our results suggest the following key steps in wing origin and diversification. First, a set of dorsally derived outgrowths evolved along a number of body segments including the first thoracic segment (T1). Homeotic genes were subsequently co-opted to suppress growth of some dorsal flaps in the thorax and abdomen. In T1 this suppression was accomplished by Sex combs reduced, that when experimentally removed, results in an ectopic T1 flap similar to prothoracic winglets present in fossil hemipteroids and other early insects. Global gene-expression differences in ectopic T1 vs. T2/T3 wings suggest that the transition from flaps to wings required ventrally originating cells, homologous with those in ancestral arthropod gill flaps/epipods, to migrate dorsally and fuse with the dorsal flap tissue thereby bringing new functional gene networks; these presumably enabled the T2/T3 wing’s increased size and functionality. Third, “fused” wings became both the wing blade and surrounding regions of the dorsal thorax cuticle, providing tissue for subsequent modifications including wing folding and the fit of folded wings. Finally, Ultrabithorax was co-opted to uncouple the morphology of T2 and T3 wings and to act as a general modifier of hindwings, which in turn governed the subsequent diversification of lineage-specific wing forms.Some 350 million years ago, the development of insect wings was a seminal event in the evolution of insect body design (1, 2). The ability to fly was critical to insects becoming the most diverse and abundant animal group, and the origin of such novelty has been a focus of intense scientific inquiry for more than a century (3, 4). More recently, through studies of genetic model systems such as Drosophila, the mechanisms of wing morphogenesis have been elucidated (5–12). Still lacking however is a comprehensive understanding of transitional steps connecting the morphology of structures observed in the fossil record with that of the modern-day insects, including wing origins and subsequent diversification.The initial stages of insect wing evolution are missing from the fossil record and it is therefore necessary to use indirect evidence from fossils that postdate the origin and initial radiation of pterygotes (2). Larvae of many of those taxa featured dorsally positioned outgrowths on each of the thoracic and abdominal segments (2, 13), apparently serial homologs (i.e., similar structures likely arising from a common set of developmental mechanisms). Diverse lineages independently lost those dorsal appendages on the abdomen while undergoing parallel modifications of wing-like structures on thoracic (T1–T3) segments. Specifically, the T1 winglets were always much smaller in fossils and apparently lacked hinge articulation whereas T2 (fore-) and T3 (hind-) wings were fully operational in adults, featuring muscles, venation, and size that rendered them capable of flapping flight (14). T1 winglets were subsequently repressed in multiple lineages (15–18) whereas T2 and T3 wings acquired morphology similar to modern day Paleoptera (mayflies and dragonflies) and other extinct paleopterous orders. The transition from Paleoptera, which rest with wings extended from the body, to Neoptera, which rest with wings folded flat against the body, required changes in the hinge mechanism, with many orders also evolving a precise mechanical fit between wing margins and the adjacent body wall of the dorsal thorax. Finally, the radiation of Neoptera encompassed a further divergence between the fore- and hindwings in terms of their shape, size, and texture (5, 19, 20). Together, this set of transitions accounts for major features of the diversity and lineage-specific wing morphologies among fossil and extant taxa.To gain insight into genetic mechanisms governing these transitional steps, we used a direct-developing neopteran species, the milkweed bug (Oncopeltus fasciatus; Hemimetabola, Hemiptera). The phylogenetic placement of Oncopeltus, basal to the more derived holometabola (e.g., flies, beetles, bees, butterflies, and so forth that have a pupal stage), is important because holometabolous appendage development occurs from imaginal discs, which are collections of cells that form and commit to appendage identity early in larval development. Oncopeltus and other hemimetabolous insects lack imaginal discs and acquire adult morphology gradually through a series of nymphal stages, similar to early fossil insects. Hence, examination of wing development in a hemimetabolous insect can help resolve the ancestral versus derived status of developmental traits present in holometabola and in general may provide new evolutionary perspectives.Oncopeltus features brightly colored forewings with a stiff proximal region and a more flexible membranous apex (hemelytra), entirely membranous hind wings, and a well-developed dorsal T2 structure (scutellum) that fits precisely against trailing edges of the folded wings. To examine wing developmental mechanisms underlying these features, we combined a candidate gene approach in which we depleted (via RNA interference, RNAi) the expression of Oncopeltus orthologs of wing specification genes, and a global approach (RNA-seq) (21) that characterized all expressed genes in wild-type T2 and T3 wings, ectopic T1 wings, and wild-type T1 body wall. The results provide independent and expanded insights into the origins and fate of T1 wings, the transition from paleoptera to neoptera, and the eventual diversification of T2 and T3 wing morphology.     

Chronic Klebsiella pneumonia: a rare manifestation of Klebsiella pneumonia

K. pneumoniae can present as two forms of community-acquired pneumonia, acute and chronic. Although acute pneumonia may turn into necrotizing pneumonia, which results in a prolonged clinical course, it often has a rapidly progressive clinical course. In contrast, chronic Klebsiella pneumonia runs a protracted indolent course that mimics other chronic pulmonary infections and malignancies. Herein, we present two cases of chronic Klebsiella pneumonia. The diagnosis was made by microorganism identification, as well as absence of other potential causes. Clinical and radiographic findings improved after a prolonged course of antibiotic therapy.     

Pulmonary actinomycosis in a male patient with a tracheal bronchus

BACKGROUND:

Tracheal bronchus is a congenital malformation comprising an abnormal bronchus originating from the trachea or other bronchus. This malformation has been associated with recurrent pneumonia in children, but is rarely associated with infection in adults. Actinomyces species are rare causes of necrotizing pneumonias that often masquerade as malignancy, lung abscesses and tuberculosis.

METHODS AND RESULTS:

A case involving a 46-year-old man with a tracheal bronchus and chronic pneumonia syndrome is presented. Bronchialveolar lavage and transthoracic needle biopsy demonstrated the presence of Actinomyces meyeri and Fusobacterium species.

CONCLUSIONS:

The present article reports the first documented case of actinomycosis occurring in a patient with a tracheal bronchus.     

Community-associated methicillin-resistant Staphylococcus aureus in a pediatric emergency department in Newfoundland and Labrador

BACKGROUND:

First-generation cephalosporins and antistaphylococcal penicillins are typically the first choice for treating skin and soft tissue infections (SSTI), but are not effective for infections caused by methicillin-resistant Staphylococcus aureus (MRSA). It is currently unclear what percentage of SSTIs is caused by community-associated MRSA in different regions in Canada.

OBJECTIVES:

To determine the incidence of MRSA in children presenting to a pediatric emergency department with SSTI, and to determine which antibiotics were used to treat these infections.

METHODS:

All visits to a pediatric emergency department were reviewed from April 15, 2010 to April 14, 2011. Diagnoses of cellulitis, abscess, impetigo, folliculitis and skin infection (not otherwise specified) were reviewed in detail to determine whether a culture was taken and which antibiotic was prescribed.

RESULTS:

There were 367 cases of SSTI diagnosed over the study period. Forty-five (12.3%) patients had lesions that were swabbed for culture and sensitivity. S aureus was the most common organism found, with 14 (66%) methicillin-sensitive cases and seven (33%) methicillin-resistant cases. Of the seven cases of MRSA identified, only one patient had clear risk factors for hospital-acquired MRSA. First-generation cephalosporins were initially prescribed for 280 (76%) patients.

CONCLUSIONS:

The overall incidence of MRSA in the population presenting to a pediatric emergency department in Newfoundland and Labrador appeared to be low, although only a small percentage of infections were cultured. At this time, there appears to be no need to change empirical antibiotic coverage, which remains a first-generation cephalosporin.     

Tribendimidine: a promising, safe and broad-spectrum anthelmintic agent from China

We review, for the first time, a 20-year Chinese story of research and development pertaining to tribendimidine, a promising anthelmintic agent that is safe and exhibits a broad spectrum of activity. Tribendimidine was first synthesized at the National Institute of Parasitic Diseases in Shanghai in the mid 1980s. In laboratory studies, tribendimidine showed high efficacy against Nippostrongylus braziliensis in rats, Necator americanus in hamsters, Ancylostoma caninum and Toxocara canis in dogs, and Syphacia mesocriceti in mice. Activity was also found against several species of cestodes in chicken. In clinical trials, a single oral dose of 400 mg tribendimidine, administered to patients infected only with N. americanus, or with N. americanus and Ancylostoma duodenalis, resulted in cure rates of 85.7% (132/154) and 89.8% (53/59), respectively. In comparison, a single oral dose of 400 mg albendazole resulted in significantly lower cure rates, namely 65.5% (91/139; chi(2) = 16.47, P < 0.001) and 71.7% (43/60; chi(2) = 6.29, P = 0.012), respectively. Single oral doses of tribendimidine (300 mg) and albendazole (400mg) were equally effective against Ascaris lumbricoides infections; cure rates were 96.0% (97/101) and 98.1% (101/103), respectively. In 5-14-year-old children with an Enterobius vermicularis infection, treated with a single oral dose of 200 mg tribendimidine, a cure rate of 81.6% (93/114) was observed. Tribendimidine was well-tolerated as only mild and transient side effects were observed. It would be of great public health significance if these findings are confirmed in other epidemiological settings, as more than one-quarter of the world population is currently affected by intestinal nematodes, with only very few drugs currently available on the market.     

Caulobacter species as a cause of postneurosurgical bacterial meningitis in a pediatric patient

Caulobacter species have been rarely found to be a cause of human infection. A case of probable Caulobacter species meningitis occurring postneurosurgery in a pediatric patient is reported in the present article. Gram stain and colony morphology of the isolate were not consistent with the identification provided by commercial phenotypic identification systems. The present case illustrates the need to reconcile conflicting phenotypic test results using 16S ribosomal DNA sequencing.     

Comparison of schistosome transmission in a single- and a double-cropped area in the rice irrigation scheme, 'Office du Niger', Mali

Rice is becoming increasingly important as a staple food in West Africa and there is a need to increase production to meet the demand and one way to achieve this is to harvest two annual crops. It is possible that such intensified irrigation could affect transmission of schistosomes and this study attempts to compare schistosome transmission in single and double-cropped areas of an irrigation scheme, 'Office du Niger', in Mali. Double cropping has been practised for some years in the Niono area while in the Kolongotomo area still only a single crop is grown. Parasitological surveys conducted in 10 villages (5 from each of these 2 areas) showed that Schistosoma haematobium was less prevalent in the area with single cropping than in the area with double cropping. In order to compare transmission patterns between the two areas, all human-water contact sites around four villages (two from each area) were identified and included in transmission studies. From August 1996 to June 1997, eight surveys were conducted, at intervals of approximately 45 days, in each of these sites to record density of the intermediate hosts, density of infected snails, environmental factors (especially density of aquatic macrophytes), and frequency of human-water contacts. Although the data provide useful information on transmission patterns in Niono and Kolongotomo areas, they fail to demonstrate clear-cut differences in snail population dynamics and transmission patterns between the two areas. A key element in snail habitats in both areas is the abundance of aquatic macrophytes, especially the submerged species. Snail control using environmental modification should focus on controlling these plants in human-water contact sites.     

Birth of a new gene on the Y chromosome of Drosophila melanogaster

Contrary to the pattern seen in mammalian sex chromosomes, where most Y-linked genes have X-linked homologs, the Drosophila X and Y chromosomes appear to be unrelated. Most of the Y-linked genes have autosomal paralogs, so autosome-to-Y transposition must be the main source of Drosophila Y-linked genes. Here we show how these genes were acquired. We found a previously unidentified gene (flagrante delicto Y, FDY) that originated from a recent duplication of the autosomal gene vig2 to the Y chromosome of Drosophila melanogaster. Four contiguous genes were duplicated along with vig2, but they became pseudogenes through the accumulation of deletions and transposable element insertions, whereas FDY remained functional, acquired testis-specific expression, and now accounts for ∼20% of the vig2-like mRNA in testis. FDY is absent in the closest relatives of D. melanogaster, and DNA sequence divergence indicates that the duplication to the Y chromosome occurred ∼2 million years ago. Thus, FDY provides a snapshot of the early stages of the establishment of a Y-linked gene and demonstrates how the Drosophila Y has been accumulating autosomal genes.The mammalian Y chromosome has the lowest gene density of any chromosome, and most of its genes have a homolog on the X. This pattern is consistent with the mammalian sex chromosomes having originated from an ordinary pair of chromosomes, followed by massive gene loss from the Y (1–4). In contrast, the closest homologs of all Drosophila melanogaster Y-linked protein-encoding genes are autosomal, strongly suggesting that its Y chromosome has been acquiring genes from the autosomes (5–7). Indeed, gene gains, and not gene losses, have played the major role in shaping the gene content of the Drosophila Y, at least in the last ∼63 million years (My) (8, 9). Hence, the Drosophila Y chromosome seems to be evolving noncanonically (10) and is an ideal model to investigate the dynamics of gene gain on a nonrecombining Y chromosome.The Drosophila Y chromosome has long been known to contain genes essential for male fertility (11, 12). Due to its heterochromatic state, progress in the molecular identification of the Y-linked single-copy genes has been slow. male fertility factor kl5 (kl-5), the first single-copy gene identified, was found serendipitously; it encodes a motor protein (dynein heavy chain) required for flagellar beating (13). More recently, a combination of computational and experimental methods identified 11 single-copy Y-linked genes among the unmapped sequence scaffolds produced by the Drosophila Genome Project (5–7). These genes have two striking features: (i) their closest paralogs are autosomal and not X linked, and (ii) they have male-specific functions, such as the beating of sperm flagella reported for the kl-5 gene (14). The most likely explanation for this pattern is that Y-linked genes were acquired from the autosomes and have been retained because they confer a specific fitness advantage to their carriers. An autosomal origin has previously been reported for a few Y-linked genes in humans and a repetitive gene on the Drosophila Y (4, 15). However, unequivocal evidence of the autosomal origin of Drosophila Y-linked genes, and of the specific mechanism that originated them, is lacking due to their antiquity. The 11 known single-copy genes (kl-2, kl-3, kl-5, ARY, WDY, PRY, Pp1-Y1, Pp1-Y2, Ppr-Y, ORY, and CCY) represent ancient duplications, with amino acid identities to the putative ancestors ranging from 30% to 74%, and poor (if any) alignment at the nucleotide level. Most of them have introns in conserved positions compared with their autosomal paralogs, ruling out retrotransposition and suggesting DNA-based duplication as the mechanism. The original size of these putative duplications is unknown, because the similarity between autosomal and Y-linked regions is restricted to one gene in each case. Flanking sequences and contiguous genes either were not duplicated or were subsequently mutated and deleted beyond recognition.Here we describe flagrante delicto Y (FDY), a single copy Y-linked gene present only in D. melanogaster, and which is 98% identical at the nucleotide level to the autosomal gene vig2. Because its origin is very recent (it occurred after the split between D. melanogaster and Drosophila simulans, ∼4 Mya), it was possible to demonstrate that FDY arose from a DNA-based duplication of chromosome 3R to the Y: the duplicated segment spans 11 kb of autosomal sequence and includes five contiguous genes (vig2, Mocs2, CG42503, Clbn, and Bili); the last four genes became pseudogenes by rapid accumulation of deletions, point mutations, and transposable element insertions or by lack of expression. Thus, FDY unequivocally demonstrates that the Drosophila Y has acquired genes from autosomes. Several Y-linked genes such as kl-2, kl-3, and PRY are shared by distant Drosophila species that diverged ∼60 Mya, implying ancient acquisitions. FDY dates the more recent acquisition to ∼2 My, and hence strongly suggests that Drosophila Y has been continuously acquiring autosomal genes.     

Vacuoles of Candida yeast as a specialized niche for Helicobacter pylori

Helicobacter pylori(H.pylori)are resistant to hostile gastric environments and antibiotic therapy,reflecting the possibility that they are protected by an ecological niche,such as inside the vacuoles of human epithelial and immune cells.Candida yeast may also provide such an alternative niche,as fluorescently labeled H.pylori were observed as fast-moving and viable bacterium-like bodies inside the vacuoles of gastric,oral,vaginal and foodborne Candida yeasts.In addition,H.pylori-specific genes and proteins were detected in samples extracted from these yeasts.The H.pylori present within these yeasts produce peroxiredoxin and thiol peroxidase,providing the ability to detoxify oxygen metabolites formed in immune cells.Furthermore,these bacteria produce urease and VacA,two virulence determinants of H.pylori that influence phago-lysosome fusion and bacterial survival in macrophages.Microscopic observations of H.pylori cells in new generations of yeasts along with amplification of H.pylori-specific genes from consecutive generations indicate that new yeasts can inherit the intracellular H.pylori as part of their vacuolar content.Accordingly,it is proposed that yeast vacuoles serve as a sophisticated niche that protects H.pylori against the environmental stresses and provides essential nutrients,including ergosterol,for its growth and multiplication.This intracellular establishment inside the yeast vacuole likely occurred long ago,leading to the adaptation of H.pylori to persist in phagocytic cells.The presence of these bacteria within yeasts,including foodborne yeasts,along with the vertical transmission of yeasts from mother to neonate,provide explanations for the persistence and propagation of H.pylori in the human population.This Topic Highlight reviews and discusses recent evidence regarding the evolutionary adaptation of H.pylori to thrive in host cell vacuoles.     

First Isolation of a Giant Virus from Wild Hirudo medicinalis Leech: Mimiviridae isolation in Hirudo medicinalis

Giant viruses and amoebae are common in freshwater, where they can coexist with other living multicellular organisms. We screened leeches from the species Hirudo medicinalis for giant viruses. We analyzed five H. medicinalis obtained from Tunisia (3) and France (2). The leeches were decontaminated and then dissected to remove internal parts for co-culture with Acanthamoeba polyphaga. The genomes of isolated viruses were sequenced on a 454 Roche instrument, and a comparative genomics analysis was performed. One Mimivirus was isolated and the strain was named Hirudovirus. The genome assembly generated two scaffolds, which were 1,155,382 and 25,660 base pairs in length. Functional annotations were identified for 47% of the genes, which corresponds to 466 proteins. The presence of Mimividae in the same ecological niche as wild Hirudo may explain the presence of the mimivirus in the digestive tract of the leech, and several studies have already shown that viruses can persist in the digestive tracts of leeches fed contaminated blood. As leeches can be used medically and Mimiviruses have the potential to be an infectious agent in humans, patients treated with leeches should be surveyed to investigate a possible connection.     

A review of amoebic liver abscess for clinicians in a nonendemic setting

Amoebic liver abscess (ALA) is an uncommon but potentially life-threatening complication of infection with the protozoan parasite Entamoeba histolytica. E histolytica is widely distributed throughout the tropics and subtropics, causing up to 40 million infections annually. The parasite is transmitted via the fecal-oral route, and once it establishes itself in the colon, it has the propensity to invade the mucosa, leading to ulceration and colitis, and to disseminate to distant extraintestinal sites, the most common of which is the liver. The authors provide a topical review of ALA and summarize clinical data from a series of 29 patients with ALA presenting to seven hospitals in Toronto, Ontario, a nonendemic setting, over 30 years.     

Laboratory and field evaluation of Teknar HP-D, a biolarvicidal formulation of Bacillus thuringiensis ssp. israelensis, against mosquito vectors

Larvicidal efficacy of Teknar HP-D, an improved biolarvicidal formulation of Bacillus thuringiensis ssp. israelensis (Bti), against Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti was determined in the laboratory, and in field the efficacy of the formulation was tested against Cx. quinquefasciatus breeding in cesspits, unused wells and drains. The toxicity of the formulation to Gambusia affinis (larvivorous fish), Notonecta sp. and Diplonychus indicus (water bugs) was also evaluated in the laboratory. Teknar HP-D was field tested at three recommended dosages, 1, 1.5 and 2l/ha, selecting five habitats for each dosage. Another five habitats were kept untreated as controls. Ae. aegypti showed greatest susceptibility to the Bti toxin in the laboratory. In cesspits, all the three dosages caused >80% reduction of pupal recruitment up to day 6 post-treatment, indicating that a weekly application at the lowest would be necessary for sustained control. The residual activity of the formulation was longer in unused wells, causing >80% reduction of pupal recruitment for 17 days from the day of treatment. In controlling pupal recruitment the three dosages produced equal effect. Application of Teknar HP-D at 1 l/ha once in three weeks is therefore recommended to control Cx. quinquefasciatus in unused wells. However, in drains, >80% reduction of pupal recruitment was observed for only 3 days and hence, application of Teknar HP-D at 2 l/ha that caused significantly higher level of reduction twice in a week at 3-day interval is necessary. At dosages from 0.032 to 3.2 mg/l (ppm), Teknar HP-D was non-toxic to Gambusia fish. The two predatory water bugs, Notonecta sp. and Diplonychus indicus that fed on the surviving larvae of Cx. quinquefasciatus exposed to the sub-lethal doses (LC(50) and LC(80)) of Teknar HP-D were safe with out having any mortality.