An efficient and green method has been developed for the synthesis of new substituted Hantzsch thiazole derivatives in 79%–90% yield, via the one-pot multi-component procedure, by the reaction of 3-(bromoacetyl)-4-hydroxy-6-methyl-2H-pyran-2-one, thiourea and substituted benzaldehydes in the presence of silica supported tungstosilisic acid, as a reusable catalyst, under conventional heating or under ultrasonic irradiation. The catalyst is recoverable by a simple filtration and can be reused in the subsequent reactions. Most of the thiazoles exhibited significant antibacterial activity compared toamoxicillin and ciprofloxacin as positive controls. In addition, the new compounds showed moderate to good antioxidant (DPPH) radical scavenging activity.
Several Bacillus strains have been well studied for their ability to control soil-borne plant diseases. This property is linked to the production of several families of lipopeptides. Depending of their structure, these compounds show antifungal and/or plant systemic resistance inducing activities. In this work, the biodiversity of lipopeptides produced by different antifungal Bacillus strains isolated from seeds, rhizospheric, and non-rhizospheric soils in Algeria was analyzed. Sixteen active strains were characterized by PCR for their content in genes involved in lipopeptide biosynthesis and by MALDI-ToF for their lipopeptide production, revealing a high biodiversity of products. The difficulty to detect kurstakin genes led us to design two new sets of specific primers. An interesting potential of antifungal activity and the synthesis of two forms of fengycins differing in the eighth amino acid (Gln/Glu) were found from the strain 8. Investigation of its genome led to the finding of an adenylation domain of the fengycin synthetase predicted to activate the glutamate residue instead of the glutamine one. According to the comparison of both the results of MALDI-ToF-MS and genome analysis, it was concluded that this adenylation domain could activate both residues at the same time. This study highlighted that the richness of the Algerian ecosystems in Bacillus strains is able to produce: surfactin, pumilacidin, lichenysin, kurstakin, and different types of fengycins.
Opportunistic infections constitute a major challenge for modern medicine mainly because the involved bacteria are usually multiresistant to antibiotics. Most of these bacteria possess remarkable ability to adapt to various ecosystems, including those exposed to anthropogenic activities. This study isolated and identified 21 multiresistant opportunistic bacteria from two polluted rivers, located in Algiers. Cadmium, lead, and copper concentrations were determined for both water samples to evaluate heavy metal pollution. High prevalence of Enterobacteria and non-fermentative Gram-negative rods was found and a nontuberculous Mycobacterium (NTM) strain was isolated. To the best of our knowledge, this is the first detection of NTM in the Algerian environment. The strains were tested for their resistance against 34 antibiotics and 8 heavy metals. Multiple antibiotics and heavy metals resistance was observed in all isolates. The two most resistant strains, identified as Acinetobacter sp. and Citrobacter freundii, were submitted to plasmid curing to determine if resistance genes were plasmid or chromosome encoded. Citrobacter freundii strain P18 showed a high molecular weight plasmid which seems to code for resistance to zinc, lead, and tetracycline, at the same time. These findings strongly suggest that anthropized environments constitute a reservoir for multiresistant opportunistic bacteria and for circulating resistance genes.
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