BEAUVERIA BASSIANA: quercetinase production and genetic diversity

Beauveria bassiana genetic diversity and ability to synthesize quercetin 2,3-dioxygenase (quercetinase) were analyzed. B. bassiana isolates, obtained from Brazilian soil samples, produced quercetinase after induction using 0.5 g/L quercetin. B. bassiana ATCC 7159 (29.6 nmol/mL/min) and isolate IP 11 (27.5 nmol/ml/min) showed the best performances and IP 3a (9.5 nmol/mL/min) presented the lowest level of quercetinase activity in the culture supernatant. A high level of polymorphism was detected by random amplified polymorphic DNA (RAPD) analysis. The use of internal-transcribed-spacer ribosomal region restriction fragment length polymorphism (ITS-RFLP) did not reveal characteristic markers to differentiate isolates. However, the ITS1-5.8S-ITS2 region sequence analysis provided more information on polymorphism among the isolates, allowing them to be clustered by relative similarity into three large groups. Correlation was tested according to the Person's correlation. Data of our studies showed, that lower associations among groups, level of quercetinase production, or geographical origin could be observed. This study presents the production of a novel biocatalyst by B. bassiana and suggests the possible industrial application of this fungal species in large-scale biotechnological manufacture of quercetinase.

Detection of entomopathogenic fungi in peridomestic triatomine-infested areas in central Brazil and fungal activity against Triatoma infestans (Klug) (Hemiptera: Reduviidae) / Detecção de fungos entomopatogênicos em áreas peridomiciliares infestadas por triatomíneos no Brasil central e atividade dos fungos contra Triatoma infestans (Klug) (Hemiptera: Reduviidae)

From 148 substrate samples collected in peridomestic triatomine-infested habitats of 24 farms in Central Brazil, 31 isolates of Metarhizium anisopliae (Metsch.) Sorok. and 15 isolates of Beauveria bassiana (Bals.) Vuill. were obtained. Most of the isolates were found in substrates that consisted of soil mixed with animal feces or soil only in areas of trees where poultry roost and pig houses. Fungi were detected with an insect bait method using Triatoma infestans (Klug), and combined in vitro and in vivo techniques with modified Chase medium and T. infestans. All isolates were highly virulent to T. infestans third instar nymphs at a relative humidity > 98 percent and temperature of 25 ± 0.5°C. However, activity against nymphs was reduced at 75 percent relative humidity. Results underline the potential of B. bassiana and M. anisopliae as agents for biological control of vectors of Chagas disease. Both species occur naturally in peridomestic habitats of triatomines in Central Brazil and may contribute to control these vectors and to reduce the risk of reinfestation of houses after eliminating domestic vector species.

Foram detectados 31 isolados de Metarhizium anisopliae (Metsch.) Sorok. e 15 isolados de Beauveria bassiana (Bals.) Vuill. em 148 amostras de substratos coletadas em habitats peridomiciliares infestados com triatomíneos de 24 fazendas localizadas no Centro do Brasil. A maioria dos isolados foi encontrada em solos misturados com fezes de animais ou solos de áreas de poleiros e chiqueiros. Os fungos foram detectados com um método de captura utilizando Triatoma infestans (Klug) como isca, e um método combinado in vitro e in vivo, com meio Chase modificado e T. infestans. Os primeiros estudos sobre a atividade dos fungos indicaram que todos os isolados foram patogênicos para T. infestans quando testados em umidade relativa acima de 98 por cento e 25 ± 0,5°C. Porém, a atividade foi reduzida em umidade relativa de 75 por cento. Os resultados ressaltam o potencial de B. bassiana e M. anisopliae como agentes de controle para os vetores da doença de Chagas. As duas espécies ocorrem naturalmente em habitats peridomiciliares de triatomíneos no Centro do Brasil e podem contribuir para o controle desses vetores e reduzir o risco de reinfestação das casas após eliminação de espécies domiciliares.

Activity of oil-formulated Beauveria bassiana against Triatoma sordida in peridomestic areas in central Brazil

Field tests were carried out during the rainy season of 2001/2002 in São Luís de Montes Belos, Goiás, Brazil, to evaluate the potential of the entomopathogenic fungus, Beauveria bassiana, against peridomestic Triatoma sordida. An oil-water formulation of the isolate CG 14 (Embrapa) was applied in triatomine infested hen houses of four farms at a final concentration of 10(6) conidia/cm². Numbers of T. sordida decreased over the next 25 days, after application of the fungus, and B. bassiana developed on dead insects in one hen house. A high number of B. bassiana colonies was detected in substrates collected in treated hen houses 24 h after application of CG 14. In the following three months the presenceof B. bassiana declined to values found before treatment.

Pathogenicity of Evlachovaea sp (Hyphomycetes), a new species isolated from Triatoma sordida, in Chagas' disease vectors

Evlachovaea sp foi testada em ninfas de 5 Triatoma spp, 5 Rhodnius spp, Panstrongylus herreri e Dipetalogaster maximus a 25ºC, 75 por cento umidade e umidade >98 por cento. A maioria das espécies foi suscetível à infecção em umidade alta. Mortalidade foi reduzida a 75 por cento de umidade. O fungo desenvolveu em 69.5 por cento dos cadáveres.

Contaminação de localidades públicas com enteroparasitos na cidade de Goiânia-Goiás-Brasil / Contamination of public localities with enteropasites in the city of Goiânia, Goiás, Brazil

A ocorrência de formas infecciosas de parasitos de animais ou do próprio homem foi estudada em localidades públicas de Goiânia, numa cidade do Centro-Oeste do Brasil. Foram examinadas 14 localidades públicas, sendo praças(7), campos de futebol(3), parques(2) e trilhas de cooper(2). Entre abril e junho de 1999 foram colhidas, semanalmente, uma amostra de fezes e uma de solo em cada localidade, que foram processadas pelos métodos de sedimentação espontânea (hoffmann et al. 1934), flutuação (Willis, 1921) e pesquisa de larvas (Rugai et al., 1954). Nototal foram analisadas 121 amostras de fezes e 121 amostras de solo. Em 85,7 por cento das localidades examinadas foram encontradas oocistos, ovos ou larvas de um ou mais parasitos. As amostras de fezes mostraram maiores índices de ovos de helmintos (33,9 por cento) que as amostras de solo (5,8 por cento)...

Development of Rhodnius prolixus (Hemiptera: Reduviidae) under constant and cyclic conditions of temperature and humidity

Development of Rhodnius prolixus after eclosion until the adult stage was studied at constant temperatures (T), 15, 20, 25, 28, 35ºC, 20/25ºC, 25/35ºC, and relative humidities (RH), 75, 86 and 97 (por cento) and fluctuating (16/8 hr) temperatures, T I/II, 15/28ºC, 25/28ºC and 25/35ºC, and relative humidities, RH I/II, 86/75 (por cento) and 97/75 (por cento). Eclosion or molting were not observed at 15ºC and 86 or 97 (por cento) RH, respectively. At 35ºC and 75 (por cento) RH only few insects molted. By alternating T I/II, 15/28ºC and 25/35ºC, insects developed at high frequency. Cumulating the average lengths of the interphases within independent groups for each instar, R. prolixus reached the adult stage most rapidly (86.7 days) and at highest frequency per instar (mean: 91.8 por cento) at 28ºC and 75 (por cento) RH. Under fluctuating T I/II, development was completed within 100 days or less at 25/28ºC and 20/25ºC (>185 days), and at constant 20ºC (>300 days). Mortality was higher at constant 97 (por cento) RH or fluctuating RH I, 97 (por cento) than at constant or fluctuating 86 (por cento) RH. Refeeding was minimal at optimal conditions of T and RH for development. The most refeeding was observed at a constant 35ºC.

Selection of Beauveria bassiana and Metarhizium anisopliae isolates to control Triatoma infestans

Twenty three isolates of Beauveria bassiana and 13 isolates of Metarhizium anisopliae were tested on third instar nymphs of Triatoma infestans, a serious vector of Chagas disease. Pathogenicity tests at saturated humidity showed that this insect is very susceptible to fungal infection. At lower relative humidity (50 per cent), conditions expected in the vector microhabitat, virulence was significantly different among isolates. Cumulative mortality 15 days after treatment varied from 17.5 to 97.5 per cent and estimates of 50 per cent survival time varied from 6 to 11 days. Maintaining lower relative humidity, four B. bassiana and two M. anisopliae isolates were selected for analysis of virulence at different conidial concentrations and temperatures. Lethal concentration sufficient to kill 50 per cent of insects (LC50) varied from 7.1x10 5 to 4.3x10 6 conidia/ml, for a B. bassiana isolate (CG 14) and a M. anisopliae isolate (CG 491) respectively. Most isolates, particularly B. bassiana isolates CG 24 and CG 306, proved to be more virulent at 25 and 30ºC, compared to 15 and 20ºC. The differential virulence at 50 per cent humidity observed among some B. bassiana isolates was not correlated to phenetic groups in cluster analysis of RAPD markers. In fact, the B. bassiana isolates analyzed presented a high homogeneity (>73 per cent similarity).