Assessment of toxic potential of local Jordanian Bacillus thuringiensis strains on Drosophila melanogaster and Culex sp. (Diptera)

AIMS: To assess the toxic potential of different local Jordanian Bacillus thuringiensis isolates on larvae of Drosophila melanogaster and Culex sp. METHODS AND RESULTS: Scanning electron microscopy revealed the presence of spherical, bi-pyramidal, and bi-pyramidal and cuboidal parasporal bodies produced by the toxic isolates. Spherical inclusions dominated. The toxicity of the isolates to the two insects, determined using 24-well plates or vials, indicated that the 50% lethal concentration (LC50) of the bacterial suspension for D. melanogaster and Culex sp. larvae varied from 4.60 to 8.65, and from 5.30 to 6.74, respectively. CONCLUSION: Comparison of the LC50 values of isolate 82 with those of the reference strain B. t. israelensis showed that this isolate has a higher toxicity potential. SIGNIFICANCE AND IMPACT OF THE STUDY: Some local Jordanian B. thuringiensis isolates exhibit toxic potential that could be used to control some important pests, and could replace chemical pesticides.     

Detection of genetic polymorphism by RAPD-PCR among isolates of Bacillus thuringiensis.

Sixteen isolates of Bacillus thuringiensis recovered from different Jordanian habitats were compared using random amplification of polymorphic DNA (RAPD) to determine whether they could be differentiated at the molecular level. Total genomic DNA from each isolate and three reference strains were amplified using 10-mer primers. Electrophoretic analysis of the amplification products revealed the incidence of polymorphism among the isolates. Pair-wise comparisons of polymorphic products were used to construct a dendrogram applying the cluster analysis. Fifteen of the isolates were all in one major cluster which was divided into six small groups. Such analysis showed some regional variation among the isolates, but did not indicate a clearly defined habitat locational pattern of the DNA polymorphism.     

Mutagenesis by ethidium bromide and N-methyl-N′-nitro-N-nitrosoguanidine in off-flavour compound producing strains ofStreptomyces

Various species of actinomycetes and cyanobacteria can impart earthy/musty off-flavours to drinking water supplies and to pond-raised fish and other aquatic food animals. The genetic determinants for production of the most common off-flavour compounds [geosmin and 2-methylisoborneol (MIB)] have not been extensively studied. An attempt has been rrlade to study the genetics of production of these compounds was demonstrated by DNA-curing analysis. The effects of two curing agents [ethidium bromide (EB) and N-methyl-N′-nitro-N-nitrosoguanidine (NTG)] on tha loss of linear plasmid DNA and generation of bald mutants (no aerial mycelia) inStreptomyces halstedii andStereptomyces violaceusniger which produce geosmin and MIB, respectively, were observed. Production of earthy/musty odour was not eliminated, but was reduced by 55–95% in the plasmid cured strain. Data suggested that off-flavour production is likely chromosomally-encoded in theseStreptomyces isolates.     

The Streptomyces flora of Jordan and its' potential as a source of antibiotics active against antibiotic-resistant Gram-negative bacteria

Detection and identification of members of the genus Streptomyces are of great value because they provide a rich source of antibiotics. Toward the goal of identifying additional novel antibiotics, a total of 292 different Streptomyces isolates were recovered from 54 soil samples collected from 28 different locations in Jordan. These were then characterized by conventional methods and assessed for their activity against two antibiotic-resistant Gram-negative isolates of Escherichia coli and Klebsiella pneumoniae. Results revealed that grey, white and yellow series isolates were the most abundant, with 15% of the Streptomyces isolates active against at least one of the test pathogens. Most of the active isolates exhibited activity against E. coli (96%), while less activity was exhibited against K. pneumoniae (18%). Overall screening revealed the characterization of six Streptomyces isolates (I₇, AC₃₂, G₁₇, Z₁₁, Bb₃₆ and AQ₁₆) which inhibited the growth of both pathogens. All were obtained from a region characterized by low-nutrient soils and harsh conditions. The unusual antibiotic profile of these isolates stressed their potential as a source of novel antibiotics.     

Old leaves accumulate more heavy metals than other parts of the desert shrub Calotropis procera at a traffic-polluted site as assessed by two analytical techniques

Abstract

Calotropis procera is a perennial big shrub that has the potential to accumulate high concentrations of heavy metals. Metal sequestration in old organs has been considered as a mechanism for plant survival in polluted soils. The aim of the present study was to assess the role of the old leaves as a sink for HMs accumulation in C. procera. Two instruments were used: atomic absorption spectroscopy (AAS) and X-ray fluorescence (XRF) microscopy. Soil and plant samples were collected from around one of the worst congested traffic areas in the United Arab Emirates (UAE). Samples from roots, stem, and green and old leaves were prepared and analyzed by both instruments. Calotropis procera was able to concentrate Fe, Mn, Sr, and Zn in the roots, but their translocation to stem and green leaves was low. Old leaves had greater ability to accumulate significantly higher concentrations of different metals, especially Fe and Sr, than other parts of the plants, indicating that C. procera uses these metabolically less-active leaves as sinks for heavy metals. Fe and Sr attained higher bioconcentration and accumulation values, compared to Zn and Mn. There were significant positive correlations between XRF and AAS for all elements in the different organs.     

Effect of glutathione L-cystein and L-djenkolic acid in the synthesis and mutagenicity of azide metabolite in Bacillus subtilis ATCC 6633 strain.

The Bacillus subtilis ATCC 6633 strain synthesizes a mutagenic metabolite from sodium azide and O-acetylserine. Mutagenicity of azide was decreased in growth media containing 10(-4) M glutathione, L-cysteine or L-djenkolic acid whereas dithiothritol (DTT) added at the same concentration did not reduce the mutagenicity of azide. Likewise, glutathione, L-cysteine, L-djenkolic acid, and DTT were found to have no effect in reducing the mutagenicity of the in vitro produced metabolite using bacterial cell-free extract. These results suggest that O-acetyl-serine sulfhydrylase catalyzes the reaction of azide and O-acetylserine to form a mutagenic metabolite, which is ninhydrin positive and migrates in TLC to an Rf value similar to that of azidoalanine in both acidic and basic solvent systems.     

Phenotypic and molecular analysis of dominant occurring antibiotic active-producing Streptomyces soil flora in Northern Jordan

This investigation aimed to determine the relatedness of dominant occurring soil Streptomyces spp. in Northern Jordan based on their RAPD-PCR fingerprints, and to compare RAPD technique with the conventional phenotypic characterization of Streptomyces isolates. Fifty-eight white and gray color-bearing aerial mycelia antibiotic active-producing Streptomyces soil isolates along with three reference strains were genetically analyzed by RAPD-PCR. Polymorphisms between the isolates showed 1 to 10 bands per isolate and ranged from 200 to 3200 bp in size. Results revealed one common band of ~600 bp shared by ~85% of the isolates, and the observation of bands specific to some reference strains and some soil isolates. When RAPD patterns were analyzed with the UPGMA, results revealed clustering the tested isolates into two equal main super clusters (50% each). Super cluster I appeared to be homogenous and include the three reference strains. However, super cluster II was heterogeneous and but not including any of the reference strains. The association of the antibiotic activity of the dominant white and gray aerial mycelium-bearing Streptomyces isolates to RAPD clustering is reported for the first time, and the RAPD-PCR fingerprints generated here deserve to be cloned, characterized and sequenced in future as Streptomyces species-specific DNA markers. The more random primers used in the analysis may add to RAPD technique a cost-effective, fast, precise result, and less labor work solution for analyzing the similarities and differences among the Streptomyces isolates.     

Genetic determinants of active antibiotic-producing soil streptomycetes.

Plasmids or covalently closed circular (CCC)-DNA molecules are abundant in the genus Streptomyces, and have been suggested to be involved in the genetic control of the production of many antibiotics in these organisms. In this study, 21 active antibiotic-producing Streptomyces isolates were screened for their plasmid content by an alkaline lysis method which revealed the presence of a small plasmid DNA in the positive control Streptomyces lividans ATCC 35287, containing pIJ702 plasmid (5.65 kb in size). However, no low molecular weight plasmids were observed in the tested antibiotic-producing Streptomyces strains suggesting that antibiotic production in these strains is likely chromosomally encoded DNA. Treatment of 2 Streptomyces strains with 10 mM ethidium bromide (EB) resulted in the failure to produce aerial mycelia and antibiotic activity.