Studies on the Biodiversity of Halophilic Microorganisms Isolated from El-Djerid Salt Lake (Tunisia) under Aerobic Conditions

Bacterial and archaeal aerobic communities were recovered from sediments from the shallow El-Djerid salt lake in Tunisia, and their salinity gradient distribution was established. Six samples for physicochemical and microbiological analyses were obtained from 6 saline sites in the lake for physico-chemical and microbiological analyses. All samples studied were considered hypersaline with NaCl concentration ranging from 150 to 260 g/L. A specific halophilic microbial community was recovered from each site, and characterization of isolated microorganisms was performed via both phenotypic and phylogenetic approaches. Only one extreme halophilic organism, domain Archaea, was isolated from site 4 only, whereas organisms in the domain Bacteria were recovered from the five remaining sampling sites that contained up to 250 g/L NaCl. Members of the domain Bacteria belonged to genera Salicola, Pontibacillus, Halomonas, Marinococcus, and Halobacillus, whereas the only member of domain Archaea isolated belonged to the genus Halorubrum. The results of this study are discussed in terms of the ecological significance of these microorganisms in the breakdown of organic matter in Lake El-Djerid and their potential for industry applications

Paenibacillus marinum sp nov., a thermophilic xylanolytic bacterium isolated from a marine hot spring in Tunisia

Among a large collection of Tunisian hot springs bacterial isolates a bacterial strain, THE22(T), with xylanolytic properties was identified. The bacterium was isolated from a natural hot spring Ain Echefa at Mediteranean sea (Korbous, North-Eastern Tunisia). The novel strain was Gram positive, spore-forming, rod-shaped, facultatively anaerobic and grew optimally under conditions of 55 degrees C, 1% (w/v) NaCl and pH 7-8. The 16S rRNA gene sequence analysis showed that strain THE22(T) fell within the radiation of the cluster comprising Paenibacillus species with Paenibacillus phyllosphaerae PALXIL04(T) as the closest phylogenetic neighbour (95.8%). The predominant components in the fatty methyl ester profile were iso-C-16:0 (34.46%), C-16:0 (19.64%), anteiso-C-15:0 (19.18%) and anteiso-C-17:0 (18.11%). The major respiratory quinone was menaquinone-7 (MK-7). The diamino acid found in the cell-wall peptidoglycan was meso-diaminopimelic acid. The base composition of DNA was 56 mol%. Based on the polyphasic taxonomic data, strain THE-22(T) (=DSM 18499(T)=LMG 23758(T)) was recognized as a novel species within the genus Paenibacillus. The name Paenibacillus marinum sp. nov. is proposed

SYNTHESIS, CRYSTAL STRUCTURE, SPECTROSCOPY PROPERTIES AND POTENTIAL ANTIMICROBIAL POTENTIALITIES OF A NEW SYNTHETIC COMPOUND: AMINO- CHLOROPYRIDINIUM DIAQUA DIOXALATO IRON(III)

We report herein the synthesis and the physicochemical characterization of a new mixed-ligand iron(III) complex of formula (C5H6ClN2)[Fe(C2O4)2(H2O)2].2H2O. This compound has been prepared by slow evaporation at room temperature and characterized by single crystal X-ray diffraction. It has been characterized by IR and UV-VIS spectra and thermal analysis (TG and DTA). In this compound, the iron ion has a slightly distorted square bipyramidal environment, coordinated by two chelating oxalate ion and two water molecules. Structural cohesion is established essentially by π-π interactions between the rings of pyridine groups and intermolecular hydrogen bonds connecting the ionic entities and uncoordinated water molecules. In vitro antimicrobial activities of the amino- chloropyridinium diaqua dioxalato iron (III) against pathogenic fungi, yeast and bacteria were studied in this work. On the whole, our new compound has high antibacterial activities against Pseudomonas aeruginosa, Staphylococcus aureus and Listeria innocua. The amino- chloropyridinium diaqua dioxalato iron (III) used at 200µg m-1, can reduce Candida albicans survival of about 45.45%, and destruct hyphe mycelial of Trichophyton rubrum. High lysozyme activities were expressed especially against Listeria innocua with 17 times more than Staphylococcus aureus. The minimal inhibitory concentrations (MIC) are ranging from 16 µg ml-1 for bacteria to 256 µg ml-1 for yeast and IC50 values varying from 1.44 to 10.45 µg ml-1 for bacteria and 45.8 for yeast. </jats:p