Sucesión bacteriana del género Bacillus en el proceso de compostaje y lombricompostaje con diferentes fuentes de estiércol

Las especies del género Bacillus ejercen un efecto positivo en las plantas debido a que inducen la producción de sideróforos, fitoestimulantes y biosurfactantes, así como compuestos con actividad inhibidora para fitopatógenos. El objetivo del trabajo fue determinar la abundancia y diversidad de la comunidad de Bacillus en el proceso de compostaje en tres diferentes estiércoles y clarificar el rol de Eisenia foetida en la colonización de esta bacteria en los lixiviados de lombricomposta. Se estableció un experimento con nueve tratamientos considerando tres fuentes de estiércol (vacuno, ovino y porcino), los lixiviados del compostaje natural y los lixiviados de lombricompostaje con Eisenia foetida. Para la identificación del género Bacillus se emplearon cultivos bacterianos de 48 h en agar y caldo nutritivo y se identificaron por las características morfológicas, físico- químicas y microbiológicas. Se estimó la cantidad máxima de unidades formadoras de colonias en estiércol crudo de ganado ovino en el orden de 62.33 x 105 UFC/g de estiércol, abundancia que se redujo a 7.00 x 104 UFC/ml en el lixiviado de composta. En estiércol crudo se aislaron 33 cepas distribuidas en 11 especies, en lixiviados de lombricomposta 24 cepas en 8 especies y en lixiviados de composta solo 18 cepas en 5 especies. Las especies más abundantes fueron B. Sporosarcina pasteurii y B. Paenibacillus alvei. Se demostró que el lixiviado de lombricomposta posee mejor uniformidad y diversidad bacteriana, por lo que debería dársele mayor uso agrícola. Abstract Species of the genus Bacillus have a positive effect on plants due they induce the production of siderophores, phytostimulants and biosurfactants as well as compounds with inhibitory activity to phytopathology. The objective of this study was to determine the abundance and diversity of Bacillus community in the composting process in three different manures and clarify the role of Eisenia foetida in the colonization of this bacterium in vermicompost leachates. An experiment was established with nine treatments considering three sources of manure (cattle, sheep and pigs), natural compost leachate and vermicomposting leachates with Eisenia foetida. To identify the genus Bacillus bacterial cultures were used for 48 h made of agar and nutrient broth and identified by morphological, physico-chemical and microbiological characteristics. The maximum number of colony forming units in raw manure of sheep was calculated in the order of 62.33 x105 CFU/g of manure, abundance was reduced to 7.00 x 104 CFU/ml in the leachate of compost. Over 33 strains belonging to 11 species were isolated from the raw manure, 24 strains from 8 species were found in the vermicompost leachate and only 18 strains from 5 species in the leachate compost. The most abundant species were B. Sporosarcina pasteurii and B. Paenibacillus alvei. It was shown that vermicompost leachate has better uniformity and bacterial diversity which should be given greater agricultural use. Keywords: Count, species, identification

Mosquito Infestation and Dengue Virus Infection in Aedes aegypti Females in Schools in Mérida, México

We determined abundance of Aedes aegypti mosquitoes and presence of dengue virus (DENV) in females collected from schools in Mérida, México, during 2008 and 2009. Backpack aspiration from 24 schools produced 468 females of Ae. aegypti and 1,676 females of another human biter, Culex quinquefasciatus. Ae. aegypti females were collected most commonly from classrooms followed by offices and bathrooms. Of these females, 24.7% were freshly fed. Examination of 118 pools of Ae. aegypti females (total of 415 females) for presence of DENV RNA produced 19 positive pools (16.1%). DENV-infected pools were detected from 11 (45.8%) of 24 schools and came from different room types, including classrooms, offices, and bathrooms. The overall rate of DENV infection per 100 Ae. aegypti females was 4.8. We conclude that schools in Mérida present a risk environment for students, teachers, and other personnel to be exposed to mosquitoes and bites of DENV-infected Ae. aegypti females