Nitrogen sources affect productivity, desiccation tolerance and storage stability of Beauveria bassiana blastospores.

AIMS: Nitrogen is a critical element in industrial fermentation media. This study investigated the influence of various nitrogen sources on blastospore production, desiccation tolerance and storage stability using two strains of the cosmopolitan insect-pathogenic fungus Beauveria bassiana. METHODS AND RESULTS: Complex organic sources of nitrogen such as soy flour, autolysed yeast and cottonseed flour induced great numbers of blastospores after 2-3 days of fermentation, which also survived drying and remained viable (32-56% survival) after 9 months storage at 4°C, although variations were found between strains. Nitrogen availability in the form of free amino acids directly influenced blastospore production and resistance to desiccation. Increasing glucose and nitrogen concentrations up to 120 and 30 g l-1 , respectively, did not improve blastospore production but enhanced desiccation tolerance. Cell viability after drying and upon fast-rehydration was increased when ≥25 g acid-hydrolysed casein per litre was supplemented in the liquid culture medium. CONCLUSIONS: These findings indicate that low-cost complex nitrogen compounds are suitable to enhance yeast-like growth by B. bassiana with good desiccation tolerance and therefore support its further scale-up production as a mycoinsecticide. SIGNIFICANCE AND IMPACT OF THE STUDY: Nitrogen is the most expensive nutrient in liquid media composition, but this study underscores the feasibility of using low-cost nitrogen compounds composed mainly of agro-industrial by-products for rapid production of desiccation-tolerant B. bassiana blastospores by liquid culture fermentation.

Effect of inoculum age and physical parameters on in vitro culture of the entomopathogenic nematode Steinernema feltiae.

Entomopathogenic nematodes (EPNs) of the families Steinernematidae and Heterorhabditidae have a symbiotic association with bacteria which makes them virulent against insects. EPNs have been mass produced using in vivo and in vitro methods, including both solid and liquid fermentation. This study assessed the effect of nematode inoculum age on the production of Steinernema feltiae in liquid, solid and biphasic processes. Several physical parameters were also assessed: the effect of medium viscosity, flask size and aeration speed on the recovery and yield of infective juveniles (IJs). Inoculum age treatments included inoculum liquid cultures that were 7, 14, 21 and 28 days old. Nematodes from the same inoculum were added to one liquid medium (liquid culture), one solid medium with bacteria previously grown in sponge (solid culture) and a variation of the solid medium (a biphasic culture), in which the bacteria were first grown in liquid and, then, soaked into the sponges, with the purpose of providing a more homogeneous bacterial culture before nematode inoculation. Experiments were conducted in Erlenmeyer flasks. Eight treatments were established involving combinations of three variables: two media (with and without 0.2% agar), two flask sizes (250 and 150 ml) and two agitation speeds (180 and 280 rpm). The study showed increases in nematode yield for liquid cultures, but not for solid or biphasic cultures, with the advance of the inoculum age up to 28 days of growth. Furthermore, the addition of 0.2% agar to the liquid medium and increasing the aeration rate by using larger flasks with higher agitation speed may increase nematode recovery and final yield. The experiments were conducted using shake flasks but the results may also be applicable for bioreactors.

Urban Jamaican children's exposure to community violence.

Exposure to violence in childhood is associated with aggression in adulthood. The high level of community violence in Jamaica is likely to expose Jamaican children to violence. There has been no detailed study of the exposure of Jamaican children to violence in their daily lives. Some 1674 urban 11-12-year-old children, previously part of a national birth cohort study, completed a questionnaire detailing their exposure to violence as witnesses, victims and aggressors. Their parents completed a socio-economic questionnaire. Jamaican children had high levels of exposure to physical violence. A quarter of the children had witnessed severe acts of physical violence such as robbery, shooting and gang wars, a fifth had been victims of serious threats or robbery and one in every twelve had been stabbed. Children reported being least exposed to sexual violence and to being shot at. Robbery was an almost universal experience affecting children from all schools and socio-economic groups. The single commonest experience as a victim of violence was the loss of a family member or close friend to murder, affecting 36.8% of children. Children's experiences of witnessing violence occurred chiefly in their communities but their personal experiences of violence occurred at school. Boys and children attending primary school had greater exposure to violence as witnesses and victims. Socio-economic status discriminated exposure to physical violence as witnesses but not as victims. Intervention strategies to reduce children's exposure to violence should include community education on the impact of exposure to violence on children, particularly the loss of a significant person, and the development of a range of school-based violence prevention programmes.

Urban Jamaican children's exposure to community violence / Niños jamaicanos en zonas urbanas expuestos a la violencia de las comunidades

Exposure to violence in childhood is associated with aggression in adulthood. The high level of community violence in Jamaica is likely to expose Jamaican children to violence. There has been no detailed study of the exposure of Jamaican children to violence in their daily lives. Some 1674 urban 11-12-year-old children, previously part of a national birth cohort study, completed a questionnaire detailing their exposure to violence as witnesses, victims and aggressors. Their parents completed a socio-economic questionnaire. Jamaican children had high levels of exposure to physical violence. A quarter of the children had witnessed severe acts of physical violence such as robbery, shooting and gang wars, a fifth had been victims of serious threats or robbery and one in every twelve had been stabbed. Children reported being least exposed to sexual violence and to being shot at. Robbery was an almost universal experience affecting children from all schools and socio-economic groups. The single commonest experience as a victim of violence was the loss of a family member or close friend to murder, affecting 36.8 of children. Children's experiences of witnessing violence occurred chiefly in their communities but their personal experiences of violence occurred at school. Boys and children attending primary school had greater exposure to violence as witnesses and victims. Socio-economic status discriminated exposure to physical violence as witnesses but not as victims. Intervention strategies to reduce children's exposure to violence should include community education on the impact of exposure to violence on children, particularly the loss of a significant person, and the development of a range of school-based violence prevention programmes

La exposición a la violencia en la niñez se halla asociada con la agresión en la edad adulta. El alto nivel de violencia comunitaria en Jamaica, tiende a exponer a los niños jamaicanos a la violencia. Hasta el momento no ha habido un estudio detallado de la exposición de los niños jamaicanos a la violencia en sus vidas diarias. Unos 1 674 niños urbanos de 11 a 12 años de edad, quienes previamente formaban parte de un estudio de cohorte de nacimientos a escala nacional, respondieron a una encuesta dando detalles de su exposición a la violencia como testigos, víctimas y agresores. Sus padres respondieron una encuesta socioeconómica. Los niños jamaicanos presentaban altos niveles de exposición a la violencia física. Una cuarta parte de los niños había sido testigo de serios actos de violencia física, tales como robo con fuerza, tiroteos y guerras entre pandillas rivales. Una quinta parte de ellos había sido víctima de serias amenazas o de robo, y uno de cada doce había sido apuñalado. Los niños informaron haber estado menos expuestos a la violencia sexual y a los disparos. El robo fue casi una experiencia universal que afectó a los niños de todas las escuelas y grupos socio-económicos. La experiencia más común en cuanto a ser víctimas de la violencia estuvo dada por la pérdida de algún miembro de la familia o algún amigo cercano por asesinado, lo cual afectó al 36.8% de los niños. Las experiencias de los niños en relación con haber sido testigos de hechos violentos, tuvieron lugar principalmente en sus comunidades, pero sus experiencias personales de violencia ocurrieron en la escuela. Los niños que asistían a la escuela primaria estuvieron más expuestos a la violencia como testigos y como víctimas. El estatus socio-económico resultó un criterio discriminante en cuanto a la exposición a la violencia física en forma de testigo, pero no como la víctima. Las estrategias de intervención para reducir este problema deben incluir la educación de la comunidad respecto al impacto de la exposición de los niños a la violencia - particularmente con respecto a la pérdida de alguna persona importante para ellos - así como el desarrollo de una serie de los programas de prevención de la violencia