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See detailMetagenomic analysis of the bacterial microbiota linked to the traditional Algerian date product "Btana"
Abekhti, Abdelkader; Taminiau, Bernard ULg; Kihal, Mabrouk et al

in Annals of Microbiology (2015)

In this study, using high throughput pyrosequencing, we highlighted the bacterial diversity of the traditional Algerian date product "Btana" that is produced in southern Algeria using both direct (DBM ... [more ▼]

In this study, using high throughput pyrosequencing, we highlighted the bacterial diversity of the traditional Algerian date product "Btana" that is produced in southern Algeria using both direct (DBM) and indirect (UBM) methods. Metagenomic analysis yielded a total of 103,379 reads, with a 606 total operational taxonomic units (OTUs) detected. Firmicutes represented 84.79 % of the total pyrosequencing reads. Phylogenetic analysis revealed that the Bacillales represented 90.20 % ± 15.12 % of the total reads. Among the phylotypes detected, Bacillus was the dominant genus (39.53 %). While Bacillus megaterium was shared among all of the samples, its distribution varied widely. Non-metric multidimensional scaling (nMDS) analysis showed that UBM samples clustered together, and three main OTUs were found in these UBM samples: Paenibacillus polymyxa, Paenibacillus xylanexedens, and Planomicrobium JN082684. Correlation analysis showed no association between parametersof the samples (age, pH, water activity) and the specific microbiota. [less ▲]

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See detailCharacterization of a novel chitinase from a moderately halophilic bacterium, Virgibacillus marismortui strain M3-23
Essghaier, Badiaa; Hedi, Abdeljabbar; Bajji, Mohammed et al

in Annals of Microbiology (2012), 62(2), 835-841

A new chitinase produced by the moderately halophilic bacterium Virgibacillus marismortui strain M3- 23 was identified and characterized. Distinguishable characteristics of high activity and stability at ... [more ▼]

A new chitinase produced by the moderately halophilic bacterium Virgibacillus marismortui strain M3- 23 was identified and characterized. Distinguishable characteristics of high activity and stability at different pH, temperatures and salinity of M3-23 chitinase are reported. Analysis of the catalytic domain sequence from the enzyme highlighted its relationship to glycosyl hydrolase family 18. Comparison of the deduced chitinase sequence from strain M3-23 to known chitinases from Bacillus species showed low similarity (82%), suggested its novelty. This is the first report of the characterization of chitinase from the species V. marismortui. The halo- and thermo-tolerant nature of the chitinolytic enzyme allows its potential use in agricultural and industrial applications. [less ▲]

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See detailMolecular characterization of plasmid-encoded ACC-1a4 β-lactamase produced by Salmonella strains isolated from water in a Tunisian hospital
Ben Aissa, Melek; Herteg Fernea, Adriana; Bouraoui, Hanene et al

in Annals of Microbiology (2012), 62

A collection of non-typhoidal Salmonella strains, designated MMB1 to MMB18, resistant to third generation cephalosporins were isolated from water in a Tunisian hospital. Isolates harbored a new blaACC ... [more ▼]

A collection of non-typhoidal Salmonella strains, designated MMB1 to MMB18, resistant to third generation cephalosporins were isolated from water in a Tunisian hospital. Isolates harbored a new blaACC gene located on a small transmissible plasmid of 5 kb. The ACC-1a4 enzyme was produced in Escherichia coli, purified and characterized. Compared to the chromosomal blaACC-1a gene, the blaACC-1a4 exhibit three mutations. We determined the kinetic parameters of our enzyme for a representative series of β-lactam substrates. The ACC-1a4 enzyme was active on penicillins and cephalosporins, nitrocefin and cephalothin being its best tested substrates. This is a real cause for alarm since these mutations showed that the DNA sequence of blaACC is an intermediate between those of blaACC-1a and blaACC-4 and might increase the probability of the appearance and spreading of ACC-4-mediated resistance in the hospital environment [less ▲]

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See detailFirst detection of a transferable blaCTX-M-14b gene in a Klebsiella pneumoniae clinical isolate from Tunisia and analysis of its genetic context
Ben Achour, Nahed; Power, Pablo; Mercuri, Paola ULg et al

in Annals of Microbiology (2012), 62

Klebsiella pneumoniae ML2508 was isolated from a patient at the surgery unit of the Military Hospital (Hôpital Militaire de Tunis), Tunisia. It was identified as a producer of extended-spectrum β ... [more ▼]

Klebsiella pneumoniae ML2508 was isolated from a patient at the surgery unit of the Military Hospital (Hôpital Militaire de Tunis), Tunisia. It was identified as a producer of extended-spectrum β-lactamases (ESBLs) by the double-disk synergy test. The β-lactamases produced by the strain were characterized by isoelectric focusing, determination of the specific activities against penicillins and cephalosporins, determination of the inhibitory concentration required to inhibit 50% of enzyme activity (IC50), and the inhibition effect of EDTA on putative metallo-β-lactamases. The crude extract of K. pneumoniae ML2508 contains five different β-lactamases with pI 5.5, 7.3, 7.6, 8.1, and 8.6. Only the β-lactamase with pI 8.1 was transferred by transformation and conjugation experiments. Molecular characterization of these genes was performed by PCR and sequencing. The four chromosomal β-lactamases are TEM (pI 5.5), 2 SHV (pI 7.3 and 7.6), and CTX-M-28 (pI 8.6). The β-lactamase with pI 8.1 was encoded byblaCTX-M-14b gene located on a 50-kb highly conjugative plasmid. The study of the genetic context of blaCTX-M-14b was realized by PCR mapping and DNA sequencing. A novel variant of tnpISEcp1 designated ISEcp1C was detected upstream of the gene. [less ▲]

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See detailThe influence of growth conditions on enterocin-like production by Enterococcus faecium CWBI-B1430 and Enterococcus mundtii CWBI-B1431 isolates from artisanal Peruvian cheeses
Aguilar Galvez, Ana Consuelo ULg; Guillermo Arciniegas, Sandra Denisse; Dubois Dauphin, Robin ULg et al

in Annals of Microbiology (2011), 61

Strains of Enterococcus faecium CWBI-B1430 and Enterococcus mundtii CWBI-B1431, isolated from artisanal-produced Peruvian cheeses, offer a broad potential application as food biopreservatives for heat ... [more ▼]

Strains of Enterococcus faecium CWBI-B1430 and Enterococcus mundtii CWBI-B1431, isolated from artisanal-produced Peruvian cheeses, offer a broad potential application as food biopreservatives for heat-processing treatments. The aim of this work was to optimize the production conditions and medium composition for the production of bacteriocin-like substances (BLIS). The kinetics of the BLIS production for both strains is a growth-associated process, and the maximum inhibitory activity for E. faecium CWBI-B1430 and E. mundtii CWBI-B1431 was achieved after 9 and 8 h of fermentation, respectively. Temperature, initial pH, oxygen level, and their interactions all influence BLIS production for both strains; this influence was specific for each strain. The bacteriocin gene expression in a 20.0-L fermentor confirms previous work carried out by fermentation in the flask; the first reports of expression revealed mundticin KS from E. faecium and enterocin P from E. mundtii. Both strains demonstrated antilisteria activity and were multi-producers of enterocin. Furthermore, the study with whey milk as an inexpensive source of fermentable carbohydrates indicated lower BLIS production than that obtained with M17LG broth. The short chain fatty acid (SCFA) analyses offer a new alternative use for both strains, as strains probiotic, for propionic acid production. [less ▲]

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See detailHigh salt-tolerant protease from a potential biocontrol agent bacillus pumilus M3-16
Essghaier, Badiaa; Bajji, Mohammed; Jijakli, Haissam ULg et al

in Annals of Microbiology (2009), 59(3), 553-558

In this paper, we investigate the characterization and evaluation of the antifungal protease activity from a halotolerant strain M3-16 of Bacillus pumilus, earlier isolated from a shallow salt lake in ... [more ▼]

In this paper, we investigate the characterization and evaluation of the antifungal protease activity from a halotolerant strain M3-16 of Bacillus pumilus, earlier isolated from a shallow salt lake in Tunisia. Protease enzyme was highly induced by the pathogen tested in vitro (27.4 U/ml). This is the first report on high salt-tolerant protease from B. pumilus, since it was active at high salinity (from 5 to 30% NaCl, w/v) as well as in the absence of salinity. This enzyme showed optimal activity at 60 °C and pH 8. At 80 °C and 30 min, the enzyme retained up to 91% and it showed stability over a wide pH range (from pH 5 to 11). The enzyme was found to be monomer with an estimated molecular mass of 31 kDa. The amino acid sequence showed high similarity (94%) to ATP-dependent protease from B. pumilus strain ATCC 7061. Thus, our alkaline thermostable and high salt-tolerant protease induced by a phytopathogenic fungus, could be useful for application in diverse areas such as biotechnology alimentary and agronomy industries. [less ▲]

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See detailCefotaxime and ceftriaxon resistant Klebsiella pneumoniae associated with SHV-11 hyperproduction
Ben Achour, Nahed; Mercuri, Paola ULg; Belhadj, Chrifa et al

in Annals of Microbiology (2008), 5(4), 727-730

Klebsiella pneumoniae ML0306 was isolated from a patient in the intensive care unit of the Military hospital of Tunis in Tunisia. The strain was resistant to β-lactams, aminoglycosides, quinolones ... [more ▼]

Klebsiella pneumoniae ML0306 was isolated from a patient in the intensive care unit of the Military hospital of Tunis in Tunisia. The strain was resistant to β-lactams, aminoglycosides, quinolones, phenicols and tetracyclines. Crude extract from the isolate showed a broad-substrate profile by hydrolyzing benzylpenicillin, ampicillin, cloxacilline, cephalothin, cefotaxime and ceftriaxone but not ceftazidime, cefoxitin, cefpirome, imipinem and aztreonam. The isolate was identified as a producer of pI 7.6 β-lactamase. Sequencing of the β-lactamase gene showed that it coded for a penicillinase SHV-11. This is the first description of this enzyme in Tunisia. The gene encoding this enzyme was located on the chromosome and a 50 kb conjugative plasmid. The overproduction of SHV-11 was involved in the wading of the hydrolytic spectrum of the strain. [less ▲]

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