Assessment of four different methods for selecting biosurfactant producing extremely halophilic bacteria

Biosurfactants are surface active agents with broad range commercial applications in various industries and have considerable advantages over their chemical counterparts. In this study, drop collapse assay, oil spreading assay, emulsification assay and surface tension measurement were compared for their reliability and ease of use to screen biosurfactant producing six extremely halophilic bacteria isolated from saline soil of Chott El Hodna-M’sila (Algeria), which is considered as a thalassohaline environment. Results from screening methods revealed that, CH2 and CH5 strains are potential candidates for biosurfactant production. Among these, there was a very strong negative linear correlation between the emulsification index and surface tension (rs= - 0.987) and a strong negative linear correlation between the oil spreading technique and surface tension (rs= - 0.971) and a weaker negative correlation between the drop collapse method and surface tension (rs= - 0.807), suggesting that strains highly active in any one of these methods were active in other three methods. As every method has its advantages and disadvantages, a combination of different methods is appropriate for a successful screening.Key words: Biosurfactant, drop collapse, emulsification stability, extremely halophilic bacteria, oil spreading, surface tension

Susceptibility of twelve soft wheat varieties (Triticum aestivum) to Sitophilus granarius (L.) (Coleoptera: Curculionidae)

International audienceThe aim of study is the effect of trophic medium of twelve soft wheat varieties on the biotic potential of S.granarius L. After 3 months of storage under laboratory conditions at 27 ± 2 ° C and 70 ± 5% rh, have reveals that the preferred varieties for development of this species are Hidhab, Mahon Demias, Arfort and Siete Ceros. This latest was found to be the most susceptible. Growth index and loss were highest with 2.08 and 3.27% respectively. Laboratory analysis of the main grain components of the different varieties suggested that the susceptibility of these varieties to S. granarius infestation may be attributed to the high content of protein and low content of carbohydrate compared to resistance varieties

Bacteriocins contributing in Rhizospheric competition among Fluorescent Pseudomonads

Aims: To examine the production of bacteriocins through the study of a group of rhizospheric Pseudomonas isolates already known to produce metabolites that are antagonistic to fungi. Methodology: Fourteen rhizospheric strains of fluorescent Pseudomonads spp., were tested as well as two referenced strains Pseudomonas protogens CHA0 and Pseudomonas aureofaciens 30-84, for their ability to produce induced bacteriocins. The induction is carried out first by UV light, and secondly by mitomycin C. Results: In addition to the reference strains, six isolates were found to produce bactericidal substances after UV light induction against Pseudomonas target bacteria but also against other genera (Escherichia and Staphylococcus). Producing strains were treated with mitomycin C, and then lysed with chloroform. Analysis of the lysates by trypsin and freezing treatments, suggests that the active compounds are of high molecular weight. Conclusion: It is therefore suggested that these bacteria could be good competitors for their introduction as biocontrol agents