Anaerobic ammonium oxidation linked to sulfate and ferric iron reduction fuels nitrogen loss in marine sediments.

Availability of fixed nitrogen is a pivotal driver on primary productivity in the oceans, thus the identification of key processes triggering nitrogen losses from these ecosystems is of major importance as they affect ecosystems function and consequently global biogeochemical cycles. Denitrification and anaerobic ammonium oxidation coupled to nitrite reduction (Anammox) are the only identified marine sinks for fixed nitrogen. The present study provides evidence indicating that anaerobic ammonium oxidation coupled to the reduction of sulfate, the most abundant electron acceptor present in the oceans, prevails in marine sediments. Tracer analysis with 15N-ammonium revealed that this microbial process, here introduced as Sulfammox, accounts for up to 5 µg 15N2 produced g-1 day-1 in sediments collected from the eastern tropical North Pacific coast. Raman and X-ray diffraction spectroscopies revealed that elemental sulfur and sphalerite (ZnFeS) were produced, besides free sulfide, during the course of Sulfammox. Anaerobic ammonium oxidation linked to Fe(III) reduction (Feammox) was also observed in the same marine sediments accounting for up to 2 µg 15N2 produced g-1 day-1. Taxonomic characterization, based on 16S rRNA gene sequencing, of marine sediments performing the Sulfammox and Feammox processes revealed the microbial members potentially involved. These novel nitrogen sinks may significantly fuel nitrogen loss in marine environments. These findings suggest that the interconnections among the oceanic biogeochemical cycles of N, S and Fe are much more complex than previously considered.

Larval habitat characterization of Anopheles darlingi from its northernmost geographical distribution in Chiapas, Mexico.

BACKGROUND: Anopheles darlingi is considered the most efficient malaria vector in the Neotropical region. In Mexico, its role as an incriminated vector of Plasmodium has not been confirmed in the Lacandon forest. Similarly, knowledge about bionomic and larval ecology is scarce. The study aim was to identify and describe the larval habitats of An. darlingi in Chiapas, México. METHODS: Standard larval collections were performed in the Lacandon forest region and in the Soconusco region of southern Chiapas from January 2010 to April 2014, including dry and rainy seasons. Mean larval density of An. darlingi was estimated according to hydrological types, and associations between the presence of An. darlingi and environmental factors including ecological parameters and geographic positions were statistically analysed. RESULTS: One hundred and twelve aquatic habitats were analysed, 80 from the Lacandon forest region and 32 from the Soconusco region; 94.64% of these sites presented anopheline larvae. In total, 10,977 larvae belonging to 11 Anopheles species were collected. The 19 (out of 112) larval habitats positive to An. darlingi were: rain puddles (26.32%), ground pools (21.05%), ponds (15.79%), ditches (15.79%), river margins (10.53%) and streams (10.53%). Overall, the average (±SD) larval density was 6.60 ± 2.41 larvae per dip. Multiple logistic regression analysis showed that temporary habitats, green algae presence and stagnant water were associated with An. darlingi larval presence. The positive habitats were found in the Lacandon forest region during the rainy season (May-September). No specimens were found in the Soconusco region of the coastal plain of Chiapas. CONCLUSION: The mosquito An. darlingi larval habitats were found in different hydrological types. The habitat stability, presence of algae and water current were the main factors for An. darlingi larval occurrence. The information on the characteristics of the larval habitats of An. darlingi will be useful in sustainable programmes for malaria control in the Lacandon forest region, Chiapas.

[Dengue-related knowledge, attitudes, and practices in primary schools in Tapachula, Chiapas, Mexico]. / Conocimientos, actitudes y prácticas sobre el dengue en las escuelas primarias de Tapachula, Chiapas, México.

OBJECTIVE: To identify dengue-related knowledge, attitudes, and practices among primary school students in Tapachula, Chiapas, Mexico, before and after an educational intervention. METHODS: The study was carried out at 19 randomly selected public primary schools. Surveys of knowledge, attitudes, and practices were conducted before and after educational sessions with fifthand sixth-grade elementary school students. The educational strategy "Escuelas sin mosquitos" ("Schools without Mosquitoes") emphasized the importance of students' participation in taking care of their schools and homes in order to prevent dengue through vector control. RESULTS: Before and after the educational sessions, a total of 3 124 surveys were conducted on the knowledge, attitudes, and practices of 1 562 fifth and sixth-grade students (772 and 790 students, respectively) between 10 and 12 years of age. The students' level of knowledge was significantly higher after the implementation of the educational strategy. In comparison with the fifth-graders, the sixth-grade students both already had and also acquired significantly more knowledge of several aspects of the disease and the vector. In all the schools, there were containers with water identified as potential breeding sites, and in 68% of the schools, these containers tested positive for Aedes aegypti larvae. CONCLUSIONS: It was demonstrated that by implementing an educational strategy, children's knowledge, attitudes, and practices were improved in terms of taking care of their schools and promoting a change of attitude to this disease at home.

Conocimientos, actitudes y prácticas sobre el dengue en las escuelas primarias de Tapachula, Chiapas, México / Dengue-related knowledge, attitudes, and practices in primary schools in Tapachula, Chiapas, Mexico

OBJETIVO: Identificar los conocimientos, actitudes y prácticas sobre el dengue en alumnos de escuelas primarias de Tapachula, Chiapas, México, antes y después de una intervención educativa. MÉTODOS: El estudio se desarrolló en 19 escuelas primarias públicas seleccionadas al azar. Se aplicaron encuestas de conocimientos, actitudes y prácticas antes y después de una estrategia educativa a alumnos de 5º y 6º grado de nivel primario. La estrategia educativa se denominó "Escuelas sin mosquitos" e hizo énfasis en la importancia de la participación de los alumnos en el autocuidado de sus escuelas y hogares para la prevención del dengue mediante el control del vector. RESULTADOS: Se aplicaron 3 124 encuestas de conocimientos, actitudes y prácticas antes y después de la estrategia educativa, a 1 562 alumnos de 5º y 6º grado (772 y 790 alumnos, respectivamente) con edades que oscilaron entre los 10 y los 12 años. El nivel de conocimiento aumentó de manera significativa en comparación con el que los alumnos tenían antes de la estrategia educativa. Los alumnos de 6º grado tenían y adquirieron significativamente más conocimiento sobre varios aspectos de la enfermedad y el vector en comparación a los de 5º grado. En todas las escuelas se hallaron recipientes con agua y 68% de las escuelas tuvieron recipientes positivos para larvas de Aedes aegypti. CONCLUSIONES: Se demostró que mediante la implementación de una estrategia educativa, aumentan el conocimiento, actitudes y prácticas de los niños sobre el autocuidado de sus escuelas y que pueden actuar como promotores del cambio de actitud sobre esta enfermedad en sus hogares.

OBJECTIVE: To identify dengue-related knowledge, attitudes, and practices among primary school students in Tapachula, Chiapas, Mexico, before and after an educational intervention. METHODS: The study was carried out at 19 randomly selected public primary schools. Surveys of knowledge, attitudes, and practices were conducted before and after educational sessions with fifthand sixth-grade elementary school students. The educational strategy "Escuelas sin mosquitos" ("Schools without Mosquitoes") emphasized the importance of students' participation in taking care of their schools and homes in order to prevent dengue through vector control. RESULTS: Before and after the educational sessions, a total of 3 124 surveys were conducted on the knowledge, attitudes, and practices of 1 562 fifthand sixth-grade students (772 and 790 students, respectively) between 10 and 12 years of age. The students' level of knowledge was significantly higher after the implementation of the educational strategy. In comparison with the fifth-graders, the sixth-grade students both already had and also acquired significantly more knowledge of several aspects of the disease and the vector. In all the schools, there were containers with water identified as potential breeding sites, and in 68% of the schools, these containers tested positive for Aedes aegypti larvae. CONCLUSIONS: It was demonstrated that by implementing an educational strategy, children's knowledge, attitudes, and practices were improved in terms of taking care of their schools and promoting a change of attitude to this disease at home.

Utilization of human DC-SIGN and L-SIGN for entry and infection of host cells by the New World arenavirus, Junín virus.

The target cell tropism of enveloped viruses is regulated by interactions between viral proteins and cellular receptors determining susceptibility at a host cell, tissue or species level. However, a number of additional cell-surface moieties can also bind viral envelope glycoproteins and could act as capture receptors, serving as attachment factors to concentrate virus particles on the cell surface, or to disseminate the virus infection to target organs or susceptible cells within the host. Here, we used Junín virus (JUNV) or JUNV glycoprotein complex (GPC)-pseudotyped particles to study their ability to be internalized by the human C-type lectins hDC- or hL-SIGN. Our results provide evidence that hDC- and hL-SIGN can mediate the entry of Junín virus into cells, and may play an important role in virus infection and dissemination in the host.

An antibody recognizing the apical domain of human transferrin receptor 1 efficiently inhibits the entry of all new world hemorrhagic Fever arenaviruses.

Five New World (NW) arenaviruses cause human hemorrhagic fevers. Four of these arenaviruses are known to enter cells by binding human transferrin receptor 1 (hTfR1). Here we show that the fifth arenavirus, Chapare virus, similarly uses hTfR1. We also identify an anti-hTfR1 antibody, ch128.1, which efficiently inhibits entry mediated by the glycoproteins of all five viruses, as well as replication of infectious Junín virus. Our data indicate that all NW hemorrhagic fever arenaviruses utilize a common hTfR1 apical-domain epitope and suggest that therapeutic agents targeting this epitope, including ch128.1 itself, can be broadly effective in treating South American hemorrhagic fevers.

Involvement of cellular proteins in Junin arenavirus entry.

Junin arenavirus (JUNV) entry is dependent on clathrin-mediated pathways and it relies on the integrity of the actin cytoskeleton as well as the dynamics of microtubules. To determine the method of entry used by this human pathogen, we have demonstrated that in Vero cells JUNV is trafficked via the cellular dynamin 2 (dyn2) endocytic pathway and it is dependent on the Eps15 GTPase. In addition, we have shown that the virus travels through Rab5-mediated early and Rab7-mediated late endosomes in its pH-dependent entry. Altogether, this study gives further inside into the endocytic pathway utilized by the arenavirus JUNV.

Involvement of cytoskeleton in Junín virus entry.

The early events in Junín virus (JUNV) infection are not thoroughly understood. We have previously shown that JUNV enter cells by clathrin-mediated endocytosis. In this report we examine the role of microfilaments and microtubules during early virus infection. Inhibitory effects of drugs affecting main cytoskeletal components on JUNV entry into Vero cells were analyzed. Drugs that disrupted microfilaments or stabilized microtubules inhibited early steps of virus entry. In contrast, drugs that stabilized microfilaments or depolymerized microtubules were not able to block virus entry very efficiently. Furthermore, real time PCR was performed to detect viral entry and we found more than 10-fold less RNA when microfilaments were depolymerized while a 100-fold diminution was seen when microtubules were stabilized. Taken together our results demonstrate that JUNV relies on an intact actin network during early infection in Vero cells while a dynamic microtubule network is also needed. This represents an important contribution to the characterization of arenavirus multiplication cycle.

Actual use of the lactational amenorrhoea method.

OBJECTIVE: The lactational amenorrhoea method (LAM) is an effective contraceptive option in developing countries. Post-partum, of the women who accept to apply LAM, many never do. Our aim was to determine the actual use of LAM. METHODS: A group of 326 post-partum women who accepted LAM use were recruited. After 6 months, they were asked if they actually had applied the method or not. In a logistic regression analysis, nine socio-demographic and clinical variables were studied as predictors of actual LAM use. An alpha level was set at 0.05. RESULTS: Overall, of the 326 women, only 61 (18.7%) actually applied LAM. The mean duration of LAM use was 4.3 +/- 0.2 months. The main reason for not applying LAM was that women thought the method was ineffective (66.0%). The variable time of menses resumption emerged as a predictor of LAM use (p = 0.001). CONCLUSIONS: Despite post-partum acceptance, most women did not actually apply LAM. In our setting as well as in other developing countries, regular contacts with a health care provider could improve LAM use.

Characterization of Junin arenavirus cell entry.

Junín virus (JUNV) entry is conducted by receptor-mediated endocytosis. To explore the cellular entry mechanism of JUNV, inhibitory effects of drugs affecting the main endocytic pathways on JUNV entry into Vero cells were analysed. Compounds that impair clathrin-mediated endocytosis were shown to reduce virus internalization without affecting virion binding. In contrast, drugs that alter lipid-raft microdomains, impairing caveola-mediated endocytosis, were not able to block virus entry. To show direct evidence of JUNV entry, transmission electron microscopy was performed; it showed JUNV particles of about 60-100 nm in membrane depressions that had an electron-dense coating. In addition, JUNV particles were found within invaginations of the plasma membrane and vesicles that resembled those of pits and clathrin-coated vesicles. Taken together, these results demonstrate that clathrin-mediated endocytosis is the main JUNV entry pathway into Vero cells and represent an important contribution to the characterization of the arenavirus multiplication cycle.

Phormidium animalis (Cyanobacteria: Oscillatoriaceae) supports larval development of Anopheles albimanus.

The capability of Phormidium animalis, a cyanobacterium commonly found in larval habitats of Anopheles albimanus in southern Mexico, to support larval development of this mosquito was investigated. First-stage larvae were reared under insectary conditions with P. animalis ad libitum and their development was compared with larvae fed with wheat germ. The time of pupation and adult mosquito size, assessed by wing length, were similar in both groups, but fewer adult mosquitoes were obtained from larvae fed with the cyanobacteria. Nevertheless, these observations indicate that P. animalis is ingested and assimilated by larval An. albimanus, making this cyanobacterium a good candidate for genetic engineering for the introduction of mosquitocidal toxins for malaria control in the region.

Cyanobacteria associated with Anopheles albimanus (Diptera: Culicidae) larval habitats in southern Mexico.

Cyanobacteria associated with Anopheles albimanus Wiedemann larval habitats from southern Chiapas, Mexico, were isolated and identified from water samples and larval midguts using selective medium BG-11. Larval breeding sites were classified according to their hydrology and dominant vegetation. Cyanobacteria isolated in water samples were recorded and analyzed according to hydrological and vegetation habitat breeding types, and mosquito larval abundance. In total, 19 cyanobacteria species were isolated from water samples. Overall, the most frequently isolated cyanobacterial taxa were Phormidium sp., Oscillatoria sp., Aphanocapsa cf. littoralis, Lyngbya lutea, P. animalis, and Anabaena cf. spiroides. Cyanobacteria were especially abundant in estuaries, irrigation canals, river margins and mangrove lagoons, and more cyanobacteria were isolated from Brachiaria mutica, Ceratophyllum demersum, and Hymenachne amplexicaulis habitats. Cyanobacteria were found in habitats with low to high An. albimanus larval abundance, but Aphanocapsa cf. littoralis was associated with habitats of low larval abundance. No correlation was found between water chemistry parameters and the presence of cyanobacteria, however, water temperature (29.2-29.4 degrees C) and phosphate concentration (79.8-136.5 ppb) were associated with medium and high mosquito larvae abundance. In An. albimanus larval midguts, only six species of cyanobacteria were isolated, the majority being from the most abundant cyanobacteria in water samples.