Predation potential of Chilocorus cacti (Coleoptera: Coccinellidae) to the prickly pear cacti pest Dactylopius opuntiae (Hemiptera: Dactylopiidae)

Functional response of the predator Chilocorus cacti (Linnaeus) (Coleoptera: Coccinellidae) on five densities of Dactylopius opuntiae (Cockerell) (Hemiptera: Dactylopiidae) female adults was assessed under laboratory conditions. The searching efficiency of C. cacti significantly decreased as prey density increased. The logistic regression for the predator had a negative and significant linear parameter indicating a type II functional response. Non-linear regression for Holling predator equation estimated a handling time of 1.79 ± 0.129 h and attack rate coefficient of 0.1003 ± 0.030. Most of this handling time was because the predator spent a lot of time removing the waxy coating that protects adult females of D. opuntiae. Chilocorus cacti consumes females of D. opuntiae in their reproductive stage; therefore, it could be an effective natural enemy to suppress or regulate low density populations of D. opuntiae, preventing them to reach high densities.

Cardiotrophin 1 protects beta cells from apoptosis and prevents streptozotocin-induced diabetes in a mouse model

AIMS/HYPOTHESIS

Cardiotrophin 1 (CT-1) is a recently described cytokine originally isolated from the heart where it has been shown to play an important role in apoptotic protection of cardiomyocytes and heart hypertrophy. Its beneficial properties have also been described in other organs such as liver and neuromuscular tissue. In the present study, we investigated whether CT-1 can confer protection against pro-apoptotic stimuli in pancreatic beta cells, and its role in insulin secretion and diabetes development.

METHODS

The effects of CT-1 on apoptosis and function were studied using MIN6B1 cells and freshly isolated murine pancreatic islets. The impact on the development of diabetes was evaluated in Ct1-null (Ct1 (-/-)) mice (the gene Ct1 is also known as Ctf1) using two streptozotocin (STZ)-induced models of diabetes.

RESULTS

CT-1 has a protective effect in MIN6B1 cells and murine islets under the pro-apoptotic stimulus of serum deprivation, which correlates with the expression of B cell lymphoma-extra large, or following exposure to a mixture of cytokines. In addition, CT-1 enhances glucose-stimulated insulin secretion in MIN6B1 cells and this was repressed by inhibitors of phospholipase C. Furthermore, Ct1 (-/-) mice were more prone to develop diabetes, and their glucose tolerance test showed impaired plasma glucose clearance which correlated with decreased pancreatic insulin secretion.

CONCLUSIONS/INTERPRETATION

The results obtained from both in vitro and in vivo experiments show that CT-1 improves beta cell function and survival, and protects mice against STZ-induced diabetes.

Acidic lipase Lip I.3 from a Pseudomonas fluorescens-like strain displays unusual properties and shows activity on secondary alcohols

AIMS

Identification, cloning, expression and characterization of a novel lipase--Lip I.3--from strain Pseudomonas CR-611.

METHODS AND RESULTS

The corresponding gene was identified and isolated by PCR-amplification, cloned and expressed in Escherichia coli, and purified by refolding from inclusion bodies. Analysis of the deduced amino acid sequence revealed high homology with members of the bacterial lipase family I.3, showing 97% identity to a putative lipase from Pseudomonas fluorescens Pf0-1, and 93% identity to a crystallized extracellular lipase from Pseudomonas sp. MIS38. A typical C-terminal type I secretion signal and several putative Ca(2+) binding sites were also identified. Experimental data confirmed that Lip I.3 requires Ca(2+) ions for correct folding and activity. The enzyme differs from the previously reported family I.3 lipases in optimal pH, being the first acidophilic lipase reported in this family. Furthermore, Lip I.3 shows a strong preference for medium chain fatty acid esters and does not display interfacial activation. When tested for activity on secondary alcohol hydrolysis, Lip I.3 displayed higher efficiency on aromatic alcohols rather than on alkyl alcohols.

CONCLUSIONS

A new family I.3 lipase with unusual properties has been isolated, cloned and described. This will contribute to a better knowledge of family I.3 lipases, a family that has been scarcely explored, and that might provide a novel source of biocatalysts.

SIGNIFICANCE AND IMPACT OF THE STUDY

The unusual properties shown by Lip I.3 and the finding of activity and enantioselectivity on secondary alcohol esters may contribute to the development of new enzymatic tools for applied biocatalysis.

Effect of environmental parameters on the inactivation of the waterborne pathogen Campylobacter in a Mediterranean river

Campylobacter is a major waterborne pathogen that can be found in rivers of the Mediterranean area. Characteristics of these rivers change throughout the seasons due to variations in environmental parameters. As these variations may affect water survival of Campylobacter, we analyzed it in the Llobregat River using three approaches whose complexity increase progressively: (i) river water microcosms in the laboratory subjected to varying temperatures; (ii) in situ experiments carried out in the river, in which bacteria were exposed to varying levels of environmental parameters; and (iii) monitoring of thermotolerant Campylobacter in the river over two years. Campylobacter was quantified using the most probable number (MPN) method. The results showed that an increase in water temperature accelerates Campylobacter inactivation, measured as the loss of culturability. In situ experiments revealed that inactivation rates were also affected by sunlight, but not by pH, oxygen concentration or water conductivity. These observations are supported by the seasonality detected in Llobregat River. Campylobacter inactivation was fastest in spring and summer, when temperature and solar radiation were at their highest. The results highlight the importance of considering the inactivation rates in natural conditions to improve the monitoring of this pathogen and thus evaluate properly the health risk associated to water.