Infection parameters of Heterorhabditis amazonensis (Nematoda: Heterorhabditidae) in different stages of Hibiscus pink mealybug.

The pink hibiscus mealybug Maconellicoccus hirsutus (Hemiptera: Pseudococcidae) is an invasive pest of an enormous variety of crops and has become a concern in many parts of the world. Early attempts to control M. hirsutus with chemical insecticides and cultural methods have failed due to the cryptic habit of the insect. We assessed the entomopathogenic nematode Heterorhabditis amazonensis as a biological agent against different insect stages. Comparing different concentrations of the nematode, insect females were very susceptible, with more than 90% of the insects killed. In second and third nymphal stages mortality rates varied from 20 to 60% depending on the nematode concentration. The first nymphal stage as much less susceptible to nematodes due to their small size. The number of nematodes capable of invading the insect host did not vary between the different concentrations. However, the LC50 for females (35.2 IJ/insect), second and third nymphal stages (83.9 IJ/insect) demonstrated that H. amazonensis should be considered as a potential biocontrol agent of the pink hibiscus mealybug.The pink hibiscus mealybug Maconellicoccus hirsutus (Hemiptera: Pseudococcidae) is an invasive pest of an enormous variety of crops and has become a concern in many parts of the world. Early attempts to control M. hirsutus with chemical insecticides and cultural methods have failed due to the cryptic habit of the insect. We assessed the entomopathogenic nematode Heterorhabditis amazonensis as a biological agent against different insect stages. Comparing different concentrations of the nematode, insect females were very susceptible, with more than 90% of the insects killed. In second and third nymphal stages mortality rates varied from 20 to 60% depending on the nematode concentration. The first nymphal stage as much less susceptible to nematodes due to their small size. The number of nematodes capable of invading the insect host did not vary between the different concentrations. However, the LC50 for females (35.2 IJ/insect), second and third nymphal stages (83.9 IJ/insect) demonstrated that H. amazonensis should be considered as a potential biocontrol agent of the pink hibiscus mealybug.

Fourier-transformed infrared spectroscopy: a tool to identify gross chemical changes from healthy to yellow band disease tissues.

Yellow band disease (YBD) is a common and wide-spread Caribbean syndrome that affects the genus Orbicella, a group of species that constitute the framework of Caribbean coral reefs. Previous studies have shown that the structure and function of bacterial assemblages vary between healthy tissues and YBD lesions; however, how the molecular composition of tissues varies as tissues transition from healthy to YBD has not been determined before. The present study provides the first survey of macromolecules found from healthy (H), apparently healthy (AH), transition (TR) and YBD tissues of Orbicella faveolata. For this, we used Fourier-transformed mid-infrared spectroscopy (FTIR) to compare absorption profiles as a proxy for the gross molecular composition of decalcified H, AH and YBD tissues. We found a significantly higher level of infrared absorption for bands assigned to lipids in H tissues compared to YBD tissues, suggesting that lipid compounds are more abundant in compromised tissues in relation to other macromolecules. We also found a lower level of intensity of bands assigned to carbohydrates and proteins in YBD tissues, compared to H and AH tissues. A similar pattern was observed for phospholipidic compounds in relation to fatty acids. This study is the first to show that healthy and YBD-compromised tissues have different infrared absorption profiles, suggesting that alterations in the biochemical composition occur during pathogenesis. Future studies should focus on determining the actual concentration of these compounds in H, AH, TR and YBD tissues and on testing the role of translocation of photoassimilates from H tissues and/or from endolithic algae to YBD tissues.

Potential role of oxidative exoenzymes of the extremophilic fungus Pestalotiopsis palmarum BM-04 in biotransformation of extra-heavy crude oil.

Large amount of drilling waste associated with the expansion of the Orinoco Oil Belt (OOB), the biggest proven reserve of extra-heavy crude oil (EHCO) worldwide, is usually impregnated with EHCO and highly salinized water-based drilling fluids. Oxidative exoenzymes (OE) of the lignin-degrading enzyme system (LDS) of fungi catalyse the oxidation of a wide range of toxic pollutants. However, very little evidences on fungal degradation or biotransformation of EHCO have been reported, which contain high amounts of asphaltenes and its biodegradation rate is very limited. The aims of this work were to study the ability of Pestalotiopsis palmarum BM-04 to synthesize OE, its potential to biotransform EHCO and to survive in extreme environmental conditions. Enzymatic studies of the LDS showed the ability of this fungus to overproduce high amounts of laccase (LACp) in presence of wheat bran or lignin peroxidase (LIPp) with EHCO as sole carbon and energy source (1300 U mgP(-1) in both cases). FT-IR spectroscopy with Attenuated Total Reflectance (ATR) analysis showed the enzymatic oxidation of carbon and sulfur atoms in both maltenes and asphaltenes fractions of biotreated EHCO catalysed by cell-free laccase-enriched OE using wheat bran as inducer. UV-visible spectrophotometry analysis revealed the oxidation of the petroporphyrins in the asphaltenes fraction of biotreated EHCO. Tolerance assays showed the ability of this fungus to grow up to 50,000 p.p.m. of EHCO and 2000 mM of NaCl. These results suggest that P. palmarum BM-04 is a hopeful alternative to be used in remediation processes in extreme environmental conditions of salinity and EHCO contamination, such as the drilling waste from the OOB.

Characterization of Xenorhabdus and Photorhabdus bacteria by Fourier transform mid-infrared spectroscopy with attenuated total reflection (FT-IR/ATR).

The use of Fourier transform mid-infrared spectroscopy with attenuated total reflection for characterizing entomopathogenic bacteria from genera Xenorhabdus and Photorhabdus is evaluated for the first time. The resulting spectra of Xenorhabdus poinarii and Photorhabdus luminiscens were compared with the spectrum of Escherichia coli samples. The absorption spectra generated by the bacteria samples, were very different at the region below 1400cm(-1) which represents the stretching vibrations of phosphate and carbohydrates. Star diagrams of the fingerprint section of nematodes spectra (between 1,350 and 1,650 cm(-1)) for separation between spectra was used and showed to be a useful tool for classification purposes.