Efficient Architecture and Implementation of Vector Median Filter in Co-Design Context

This work presents an efficient fast parallel architecture of the Vector Median Filter (VMF) using combined hardware/software (HW/SW) implementation. The hardware part of the system is implemented using VHDL language, whereas the software part is developed using C/C++ language. The software part of the embedded system uses the NIOS-II softcore processor and the operating system used is μClinux. The comparison between the software and HW/SW solutions shows that adding a hardware part in the design attempts to speed up the filtering process compared to the software solution. This efficient embedded system implementation can perform well in several image processing applications

Genetic and biochemical diversity of Paenibacillus larvae isolated from Tunisian infected honey bee broods

Paenibacillus larvae is the causative agent of American foulbrood (AFB), a virulent disease of honeybee (Apis mellifera) larvae. In Tunisia, AFB has been detected in many beekeeping areas, where it causes important economical losses, but nothing is known about the diversity of the causing agent. Seventy five isolates of P. larvae, identified by biochemical tests and 16S rRNA gene sequencing, were obtained from fifteen contaminated broods showing typical AFB symptoms, collected in different locations in the northern part of the country. Using BOX-PCR, a distinct profile of P. larvae respect to related Paenibacillus species was detected which may be useful for its identification. Some P. larvae-specific bands represented novel potential molecular markers for the species. BOX-PCR fingerprints indicated a relatively high intraspecific diversity among the isolates not described previously with several molecular polymorphisms identifying six genotypes on polyacrylamide gel. Polymorphisms were also detected in several biochemical characters (indol production, nitrate reduction, methyl red and oxidase test). Contrary to the relatively high intraspecies molecular and phenotypic diversity, the in-vivo virulence of three selected P. larvae genotypes did not differ significantly, suggesting that the genotypic/phenotypic differences are neutral or related to ecological aspects other than virulence

Production and partial characterization of chitinase from a halotolerant Planococcus rifitoensis strain M2-26

peer reviewedThis paper is the first to investigate the production and partial characterization of the chitinase enzyme from a moderately halophilic bacterium Planococcus rifitoensis strain M2-26, earlier isolated from a shallow salt lake in Tunisia. The impact of salt, salinity concentration, pH, carbon and nitrogen sources on chitinase production and activity have been determined. This is the first report on a high salt-tolerant chitinase from P. rifitoensis, since it was active at high salinity (from 5 to 30% NaCl) as well as in the absence of salt. This enzyme showed optimal activity at 70 C and retained up to 82 and 66% of its original activity at 80 or 90 C, respectively. The activity of the enzyme was also shown over a wide pH range (from 5 to 11). For characterization of the enzyme activity, the chitinase secreted in the culture supernatant was partially purified. The preliminary study of the concentrated dialysed supernatant on native PAGE showed at least three chitinases produced by strain M2-26, with highest activity approximately at 65 kDa. Thus, the thermo-tolerant and high salt-tolerant chitinases produced by P. rifitoensis strain M2-26 could be useful for application in diverse areas such as biotechnology and agro-industry

Assessment of the genetic diversity of Frankia microsymbionts of Elaeagnus angustifolia L. plants growing in a Tunisian date-palm oasis by analysis of PCR amplified nifD-K intergenic spacer

Diversity of Frankia microsymbionts of non-native Elaeagnus angustifolia L. plants spontaneously growing in a Tunisian desertic retreat area, the date-palm oasis of Tozeur, was investigated by polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) and PCR-sequencing techniques targeting the nifD-K intergenic spacer. Three PCR-RFLP haplotypes (I, II, and III) were detected among collected nodules. Haplotype I was detected at all five sampling sites and dominated the other haplotypes present at these sites. This haplotype was also exhibited by strain BMG5.10, which was isolated by a plant-capturing assay in 1998 from soil collected in the same locality, qualifying it to be the most competitive haplotype in the edapho-climatic condition of the studied desertic date-palm oasis. nifD-K sequences of the three haplotypes formed a closely related phylogenetic subgroup. These results suggest that Frankia variability is constrained by severe edapho-climatic conditions of retreated desert in Tunisian area

Occurrence and diversity of Frankia in Tunisian soil

There is a lack of studies on the occurrence and diversity of Frankia in African soils, including those in northern African regions. The present study on Tunisian soils is an attempt to address this issue using Alnus glutinosa, Elaeagnus angustifolia and Casuarina glauca in a plant capturing bioassay on 30 soil samples, followed by amplified 16S ribosomal DNA restriction pattern analysis (ARDRA). A total of seven ARDRA haplotypes of Frankia have been detected in root actinorhizas that have been affiliated to theoretical ARDRA haplotypes upon in silico digestion of selected 16S ribosomal RNA (rRNA) gene sequences retrieved from GeneBank and confirmed by their partial 16S rRNA gene sequencing. Elaeagnus-compatible Frankia isolates were widespread and form four ARDRA haplotypes affiliated to Frankia, colonizing Elaeagnaceae and Rhamnaceae in two different phylogenetic subgroups. Alnus-compatible strains occurring in northern subhumid area were closely related to Alnus-Morella-compatible strains and clustered in two ARDRA haplotypes. Casuarina-compatible strains lack variability in several northern arboreta. The relatively wide diversity of Tunisian Frankia strains opens the perspective that African soil could be an interesting reservoir for the isolation of new actinorhizal strains that could be used as potential biofertilizers to counteract the progressive soil desertification which indeed is a crucial environmental problem in Northern Africa

Screening of plant growth promoting traits of Bacillus thuringiensis

This study aimed to evaluate the plant growth promoting (PGP) potential of Bacillus thuringiensis. In this context, several genetic determinants of factors implicated in PGP potential were investigated by polymerase chain reaction (PCR) in 16 B. thuringiensis strains of different origin and belonging to different subspecies. PCR screening was performed on acid phosphatase, phytase, siderophore biosynthesis protein, 1-aminocyclopropane-1-carboxylate (ACC) deaminase and indolpyruvate decarboxylase (ipdC). Production of indol acetic acid (IAA)-like compounds and of ACC deaminase, and capability of solubilising mineral phosphate were investigated by phenotypic tests. All the strains were PCR positive for the presence of the siderophore biosynthesis protein, ACC deaminase and acid phosphatase genes. Five and seven strains gave an amplicon with the expected length for the phytase and ipdC genes respectively. All the strains produced IAA compounds and seven had a high capacity to solubilise inorganic phosphorous. Qualitative phenotypic test for ACC deaminase activity showed that seven strains are able to grow on salt minimal medium containing ACC as sole nitrogen source, indicating the expression of the accd genes. Our screening results in thirteen strains having more than one PGP trait and showed that B. thuringiensis harbours and expresses several PGP determinants that could be very interesting in field application to enhance the plant growth. To our knowledge, this is the first report on the multiple plant growth promoting potential of B. thuringiensis

Heteroduplex structures in 16S-23S rRNA intergenic transcribed spacer PCR products reveal ribosomal interoperonic polymorphisms within single Frankia strains

Aims: Detection of polymorphisms in intergenic transcribed spacer (ITS) 16S-23S rRNA within single Frankia strains. Methods and Results: Polymorphisms in the 16S-23S rRNA ITS were investigated in single-colony subcultures of seven Frankia isolates. Multiple ITS-polymerase chain reaction (PCR) bands were detected solely in isolates BMG5.5 and BMG5.11. The slow-migrating bands in the ITS-PCR agarose gel electrophoresis profiles of the isolates were revealed to be heteroduplexes on the basis of their migration shift in different electrophoretic matrices, southern hybridization and the single-strand DNA mung bean endonuclease digestion. Laser-scanned capillary electrophoresis detected two ITS-PCR fragments differing in length by three and six nucleotide insertions/deletions in strains BMG5.5 and BMG5.11, respectively. Sequence analysis of the cloned ITS showed that in strain BMG5.5 the two ITS differed by the presence of three to four copies of the 3-bp tandem repeat 5′-TGG-3′. In strain BMG5.11, the two ITS differed by the presence of two to three copies of the 6-bp tandem repeat 5′-CTTGGG-3′. Conclusions: We demonstrate the occurrence of ITS 16S-23S rRNa polymorphisms within single Frankia strains. Significance and Impact of the Study: We reported the occurrence of ITS 16S-23S rRNA polymorphisms within single Frankia strains from Elaeagnus host group recognized as the more flexible strains within Frankia genus. Furthermore, we underscored the applied interest of strains BMG5.11 and BMG5.5 in future ecological studies using ITS 16S-23S rRNA as molecular marker