Do container size and predator presence affect Culex (Diptera: Culicidae) oviposition preferences?

Organisms with complex life cycles typically do not exhibit parental care. Hence, the ability of adult females to choose quality oviposition sites is critical for offspring success. Gravid females of many insect taxa have the capability to detect environmental conditions in water-holding containers (e.g., resource level, presence of competitors or predators) and to choose the sites that are most suitable for offspring growth and development. Mosquitoes may also detect physical container characteristics related to water permanence such as surface area, volume, or container size, and some species such as those in the genus Culex have been shown to prefer larger containers. However, predators may also preferentially colonize larger containers; thus, ovipositing females may face decisions based on cues of site quality that balance the costs and benefits for offspring. We used a field experiment to evaluate the oviposition preferences of two Culex species in response to experimental container size and predator abundances within the containers. We found that both species avoided ovipositing in the largest containers, which have high abundances of Chaoborus sp. and dragonfly larvae (predators). However, the container size most commonly chosen for oviposition (15-L buckets) also had high mean abundance per liter of dragonfly larvae. These results suggest either prey naiveté or reduced vulnerability of these species to dragonflies compared to Chaoborus sp. Other potential mechanisms for the observed patterns are discussed.     

Isolation and molecular characterization of Bacillus thuringiensis found in soils of the Cerrado region of Brazil,and their toxicity to Aedes aegypti larvae

This study investigated the potential of Bacillus thuringiensis isolates obtained in the Cerrado region of the Brazilian state of Maranhão for the biological control of Aedes aegypti larvae. The isolates were obtained from soil samples and the identification of the B. thuringiensis colonies was based on morphological characteristics. Bioassays were run to assess the pathogenicity and toxicity of the different strains of the B. thuringiensis against third-instar larvae of A. aegypti. Protein profiles were obtained by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Polymerase chain reaction assays were used to detect the toxin genes found in the bacterial isolates. Overall, 12 (4.0%) of the 300 isolates obtained from 45 soil samples were found to present larvicidal activity, with the BtMA-104, BtMA-401 and BtMA-560 isolates causing 100% of mortality. The BtMA-401 isolate was the most virulent, with the lowest median lethal concentration (LC₅₀) (0.004 × 10⁷ spores/mL), followed by the Bacillus thuringiensis var. israelensis standard (0.32 × 10⁷ spores/mL). The protein profiles of BtMA-25 and BtMA-401 isolates indicated the presence of molecular mass consistent with the presence of the proteins Cry4Aa, Cry11Aa and Cyt1, similar to the profile of Bacillus thuringiensis var. israelensis IPS-82. Surprisingly, however, none of the cry and cyt genes analyzed were amplified in the isolate BtMA-401. The results of the present study revealed the larvicidal potential of B. thuringiensis isolates found in the soils of the Cerrado region from Maranhão, although further research will be necessary to better elucidate and describe other genes associated with the production of insecticidal toxins in these isolates.     

Brazilian species of Calliandra Benth. (tribe Ingeae) are nodulated by diverse strains of Paraburkholderia

The Chapada Diamantina in NE of Brazil is a biodiversity hotspot and a center of radiation for many Neotropical legume genera, such as Calliandra and Mimosa. The present study aimed to evaluate nodulation in Calliandra species endemic to various environments, and to characterize the diversity of their symbiotic rhizobia using housekeeping (16S rRNA, recA) and plasmid-borne, symbiosis-related (nifH and nodC) genes. The nodulation ability of selected isolates was assessed. All of the 126 bacterial isolates from 18 Calliandra species collected in six different vegetation types were identified as Paraburkholderia according to their housekeeping and symbiosis gene phylogenies. They were grouped in seven clades in relation to the dominant vegetation type in their native environments. The majority, particularly those from highland “campo rupestre” vegetation, were similar to Paraburkholderia nodosa, but had nodC genes identical to the Mimosa symbiont Paraburkholderia tuberum sv. mimosae. The other smaller groups were related to Paraburkholderia diazotrophica and Paraburkholderia sabiae, and some single strains were not close to any known species. The symbionts of Calliandra spp. in NE Brazil are Paraburkholderia strains closely-related to Mimosa symbionts from the same region. NE Brazil is a reservoir of symbiotic Paraburkholderia that have an affinity for genera in the Mimosoid clade.     

Volatile compounds flavoring obtained from Brazilian and Mexican spirit wastes by yeasts

Vinasse is a waste obtained from the production of beverages, such as tequila and cachaça. The presence of acids, alcohols, sugars, minerals, amino acids, peptides, and nitrogen salts make vinasse a hazardous liquid waste to the environment, affecting the fauna, flora, and microbiota of rivers and lagoons. This study used biological treatment concomitant to volatile compound production. The yeasts used in the study were Saccharomyces cerevisiae (CCMA 0187 and CCMA 0188), Candida parapsilosis (CCMA 0544), and Pichia anomala (CCMA 0193). A higher percentage reduction in chemical and biochemical oxygen demand was observed in the tequila vinasse than in the cachaça vinasse. However, a higher production of volatile compounds was observed in the cachaça vinasse. C. parapsilosis CCMA 0544 produced the highest concentration of 2-phenylethanol (162 mg L^?1). These results indicated that the environmental damage of vinasse can be reduced by treating vinasse with yeasts, and this treatment produces aroma compounds. This biological treatment has high economic potential, especially for the tequila industry.     

Phylogeny contributes more than site characteristics and traits to the spatial distribution pattern of tropical tree populations

Dispersal mechanism, species height, sexual system, and wood density are potential drivers of the spatial distribution pattern of tropical tree populations. These traits are usually conserved among closely related species, thus populations of these species should have more similar spatial distribution patterns than populations of phylogenetically distant species. Additionally, variation in the abiotic and biotic environment might result in distinct spatial distribution patterns of local populations of the same species. We employed variation partitioning to determine the degree to which traits, shared evolutionary history, site characteristics, and their joint effects govern the degree of overdispersion or aggregation of tree populations at different spatial scales within fourteen 1‐ha plots of the Atlantic Rainforest in southeastern Brazil. We quantified the degree of overdispersion or aggregation with a new standardized index err(r) based on standardized effect sizes of the pair correlation function. Variation in err(r) was mostly explained by phylogenetic relationships among species (70–95%, depending on spatial scale), indicating that traits not included in our analysis are important drivers of the spatial distribution pattern. Site characteristics explained a smaller part of the variation, indicating context‐dependence. Finally, the traits studied here provided the smallest explanation of the variation, suggesting a minor role of seed dispersal. Residual variation in err(r) ranged from 5–29%, indicating that stochasticity and/or variables not included in the models (e.g. direct measures of post‐dispersal processes) also influence the spatial distribution pattern of the populations. Our results suggest that many ecological processes act in concert at the study site and that their importance changes with spatial scale. Additionally, the relative importance of these processes differs from that previously described for other tropical forests. Determining why a given ecological process is more important in some tropical tree communities than in others are promising venues for further research.     

Spatial relationship between the nucleotide-binding site, Lys-61 and Cys-374 in actin and a conformational change induced by myosin subfragment-1 binding

The spatial relationship between Lys-61, the nucleotide binding site and Cys-374 was studied. Lys-61 was labelled with fluorescein-5-isothiocyanate as a resonance energy acceptor, the nucleotide-binding site was labelled with the fluorescent ATP analogues epsilon ATP or formycin-A 5'-triphosphate (FTP) and Cys-374 was labelled with 5-(2-[(iodoacetyl)amino]ethyl)aminonaphthalene-1-sulfonic acid (1,5-IAEDANS) as a resonance energy donor. The distances between the nucleotide binding site and Lys-61 or between Lys-61 and Cys-374 were calculated to be 3.5 +/- 0.3 nm and 4.60 +/- 0.03 nm, respectively. (The assumption has been made in calculating these distances that the energy donor and acceptor rotate rapidly relative to the fluorescence lifetime.) On the other hand, when doubly-labelled actin with 1,5-IAEDANS at Cys-374 and FITC at Lys-61 was polymerized in the presence of a twofold molar excess of phalloidin [Miki, M. (1987) Eur. J. Biochem. 164, 229-235], the fluorescence of 1,5-IAEDANS bound to actin was quenched significantly. This could be attributed to inter-monomer energy transfer. The inter-monomer distance between FITC attached to Lys-61 in a monomer and 1,5-IAEDANS attached to Cys-374 in its nearest-neighbour monomer in an F-actin filament was calculated to be 3.34 +/- 0.06 nm, assuming that the likely change in the intra-monomer distance does not change during polymerization by more than 0.4 nm. One possible spatial relationship between Lys-61, Cys-374 and the nucleotide binding site in an F-actin filament is proposed. The effect of myosin subfragment-1 (S1) binding on the energy transfer efficiency was studied. The fluorescence intensity of AEDANS-FITC-actin decreased by 30% upon interaction with S1. The fluorescence intensity of AEDANS-FITC-actin polymer in the presence of phalloidin increased by 21% upon interaction with S1. The addition of ATP led to the fluorescence intensity returning to the initial level. Assuming that the change of fluorescence intensity can be attributed to conformational change in the actin molecule induced by S1 binding, the intra-monomer distance was reduced by 0.4 nm and the inter-monomer distance was increased by 0.2 nm.     

Morbidity of schistosomiasis in Brazil. IV--Course in treated patients and their controls

A comparative study on the evolutive morbidity of schistosomiasis mansoni in treated and non-treated patients in an endemic area was carried-out with evaluation of the treatment after one and six years. In the first year after treatment there was both an improvement in the clinical conditions and a dramatic reduction in the number of S. mansoni eggs eliminated by the treated patients in relation to the controls. However, after six years of observations, although the number of S. mansoni eggs eliminated by the treated patients was still less than in the control group, it was nearly the same number as before treatment. In both treated and non-treated groups there was an increase in the severity of the clinical forms of schistosomiasis, with a certain tendency of greater severity in the control group. Therefore the authors recommend that the specific treatment of the population in endemic area should be done at intervals of two to three years, and that the treatment should be associated to the environmental sanitation, water supply and the education of the population.     

Reduction of Tubulin Expression in Angomonas deanei by RNAi Modifies the Ultrastructure of the Trypanosomatid Protozoan and Impairs Division of Its Endosymbiotic Bacterium

In the last two decades, RNA interference pathways have been employed as a useful tool for reverse genetics in trypanosomatids. Angomonas deanei is a nonpathogenic trypanosomatid that maintains an obligatory endosymbiosis with a bacterium related to the Alcaligenaceae family. Studies of this symbiosis can help us to understand the origin of eukaryotic organelles. The recent elucidation of both the A. deanei and the bacterium symbiont genomes revealed that the host protozoan codes for the enzymes necessary for RNAi activity in trypanosomatids. Here, we tested the functionality of the RNAi machinery by transfecting cells with dsRNA to a reporter gene (green fluorescent protein), which had been previously expressed in the parasite and to α‐tubulin, an endogenous gene. In both cases, protein expression was reduced by the presence of specific dsRNA, inducing, respectively, a decreased GFP fluorescence and the formation of enlarged cells with modified arrangement of subpellicular microtubules. Furthermore, symbiont division was impaired. These results indicate that the RNAi system is active in A. deanei and can be used to further explore gene function in symbiont‐containing trypanosomatids and to clarify important aspects of symbiosis and cell evolution.