Isolation, characterization, and hydrolytic activities of Geobacillus species from Jordanian hot springs

The present study was conducted to isolate, identify, characterize and to determine the enzymatic activities of the thermophilic Geobacillus species from five Jordanian hot springs. Based on phenotypic characters, eight thermophilic isolates were identified and belonged to the genus Geobacillus. The Geobacillus isolates were abundant in all investigated hot springs. The optimal temperature for growth of the isolates was 60 to 65°C and the optimal pH was 6 to 8. Colonies were light yellow circular to rhizoid. The bacterial cells were Gram positive rods and endospore forming. All isolates produced amylase, caseinase, alkaline and acid phosphatases, esterase (C4), esterase lipase (C8), α-Galactosidase, β-Glucuronidase, β-Glucosidase, and N-Acetyl-β-glucosaminidase. Seven isolates produced leucine and valine arylamidases and five isolates produced naphthol-AS-B1- phsphohydrolase. Lipase (C14) activity from two isolates and α-chymotrypsin activity from three isolates were also detected. The phenotypic characterization of those isolates was confirmed by genotypic method using 16S rDNA sequence analysis. Maximal homology of all eight  isolates to genus Geobacillus was observed. Five of these isolates showed greater than 98% homology with Geobacillus stearothermophilus and one isolate showed 100% homology with Geobacillus thermoglucosidasius. Therefore, 16S rRNA gene sequence analysis can be considered as a valuable genotypic tool for the identification and characterization of thermophilic bacteria at genus level. Moreover, enzymatic products of those isolates could receive considerable attention due to their potential applications in biotechnology.Keywords: Thermophiles, Geobacillus, hydrolytic enzymes, hot spring, 16S rRNA

Antimicrobial peptides expression by ocular surface cells in response to Acanthamoeba castellanii: an in vitro study

International audienceAims: Antimicrobial peptides (AMPs) are natural effectors of the innate immune response. Much work has been done to study their response and effects on bacterial and viral infection. Little if any information is available in relation to protozoal infections. Our aim was to comprehensively study the gene expression of the ocular AMPs in human corneal limbal epithelial cells (HCLE) stimulated with Acanthamoeba castellanii (AC). Methods: Human corneal limbal epithelial cells were exposed to AC at different time points, up to 9 hours, the genomic profile of the AMPs were analysed at these time point using real time PCR. HCLE cells not infected with AC were used as controls. Results: Seven of the 8 studied AMPs showed statistically significant upregulation in gene expression. Human beta Defensin 3 (hBD3) showed a very significant 10 fold upregulation in the exposed cells and Ribonuclease-7 (RNase-7) showed a very early and consistent increase. Human beta Defensin 1 (hBD1) was the only downregulated AMP. Conclusions: The study data suggests a possible role of the AMPs in combating the amoebic infection at the ocular surface. Using AMPs singly or in combination is a promising avenue for further exploration in the treatment of the sight threatening Acanthamoeba keratitis