Marjolaine Martin

Microorganisms living on macroalgae: diversity, interactions, and biotechnological applications

Marine microorganisms play key roles in every marine ecological process, hence the growing interest in studying their populations and functions. Microbial communities on algae remain underexplored, however, despite their huge biodiversity and the fact that they differ markedly from those living freely in seawater. The study of this microbiota and of its relationships with algal hosts should provide crucial information for ecological investigations on algae and aquatic ecosystems. Furthermore, because these microorganisms interact with algae in multiple, complex ways, they constitute an interesting source of novel bioactive compounds with biotechnological potential, such as dehalogenases, antimicrobials, and alga-specific polysaccharidases (e.g., agarases, carrageenases, and alginate lyases). Here, to demonstrate the huge potential of alga-associated organisms and their metabolites in developing future biotechnological applications, we first describe the immense diversity and density of these microbial biofilms. We further describe their complex interactions with algae, leading to the production of specific bioactive compounds and hydrolytic enzymes of biotechnological interest. We end with a glance at their potential use in medical and industrial applications.

Identification and Characterization of a Halotolerant, Cold-Active Marine Endo-β-1,4-Glucanase by Using Functional Metagenomics of Seaweed-Associated Microbiota

ABSTRACT A metagenomic library was constructed from microorganisms associated with the brown alga Ascophyllum nodosum. Functional screening of this library revealed 13 novel putative esterase loci and two glycoside hydrolase loci. Sequence and gene cluster analysis showed the wide diversity of the identified enzymes and gave an idea of the microbial populations present during the sample collection period. Lastly, an endo-β-1,4-glucanase having less than 50% identity to sequences of known cellulases was purified and partially characterized, showing activity at low temperature and after prolonged incubation in concentrated salt solutions.

Biotechnological potential of the microflora associated with the brown alga Ascophyllum nodosum

........................................................................................................................... for presenting the oral talk entitled: ........................................................................................................................... ...........................................................................................................................T mucosal surfaces are important sites of entry for a majority of microorganism, and viruses in particular. Equine Herpesvirus type 1 (EHV-1) is an example of an invasive virus of the airway mucosa. An essential prerequisite for an effective host attack of the virus is to breach the epithelial cell layer and the underlying Basement Membrane (BM) barrier. In our research, nasal mucosa explants were inoculated with EHV-1 and then double immunofluorescence staining was performed to detect viral antigen positive cells as well as integrin alpha 6, laminin, collagen IV and collagen VII. The breadth of these extracellular matrix proteins was measured in Regions Of Interest (ROI) at a magnification of 200X. ROI were defined beneath non-infected and infected regions. In infected regions, the percentage of ROI were significantly decreased for integrin alpha 6 after 24 hours and 48 hours of inoculation. However, infection did not alter the percentages for laminin and collagen IV. For collagen VII, an increase in the percentage could be observed underneath EHV-1-infected plaques only at 48 hours of inoculation. In conclusion, the results revealed a substantial impact of EHV-1 infection on integrin alpha 6 and collagen VII, two important components of the extracellular matrix, which are normally associated with the basement membrane and may play a role in virus penetration to underlying tissues.T study was aimed to evaluate the effect of Milbond (HSCAS) on aflatoxin M1 in artificially contaminated cow’s milk. Chemisorption compounds used in this experiment were MIlBond, hydrated sodium calcium aluminosilicate (HSCAS). Raw cow milk were artificially exposed to aflatoxin M1 in a concentration of 100 ppb) with addition of Nilbond at 0.5, 1, 2 and 3 % at room temperature for 30 minutes. Aflatoxin M1 was decreased more than 95% by HSCAS at 2%. Milk composition consist of protein, fat, lactose, solid non fat and total solid were affected by addition of some adsorbents were not significantly affected (p 0.05). Tthis method did not involve degrading the toxin, milk may be free from toxin degradation products and is safe for consumption. In addition, the added material may be easily separated from milk after the substance adsorbs the toxin. Thus, this method should be developed by further researches for determining effects of these compounds on functional properties of milk. The ability of hydrated sodium calcium aluminosilicate to prevent or reduce the level of aflatoxin MI residues in milk is critically needed. This finding has important implications, because milk is ultimately consumed by humans and animals, and the reduction of aflatoxin contamination in the milk could have an important impact on their health.The presence of viable bacteria in the blood is commonly known as bacteremia. It can be a very localized and transient event with no consequences but for the immune-suppressed or seriously wounded people. The most severe cases can develop into sepsis, septic shock and sometimes death. Faced with suspected bacteremia, a practitioner is forced to use a broad spectrum antibiotic treatment while awaiting the results of microbiological analyses of blood samples which can last for 24 hours to 72 hours. Despite numerous efforts to shorten the time required for diagnosis, in most techniques the organism identification begins only after the blood culture turns positive. Staphylococcus aureus is one of the most frequent strains causing bacteremia. For this reason, its detection is a major challenge for health issues. We propose here to carry out the microorganism identification directly from blood culture phase. To achieve this, live bacteria are detected on an antibody based biochip without any labeling. This approach relies on a simple to operate optical technique named Surface Plasmon Resonance imaging (SPRi), recently described for pathogen detection in complex samples (ground meat, milk). Biological samples are diluted in a media specifically dedicated to this application and in accordance with the recommendations for blood cultures. Then, samples are spiked with a known amount of S. aureus and loaded on the biochip. Interactions are then recorded in real time until a positive signal appears on specific antibody due to antibody-antigen recognition. In general, a few dozens of bacteria are detected in less than ten hours in human serum. We are now focusing on the methicillin-resistant strain (MRSA versus MSSA), by the identification of the PBP2a protein, which is anchored at the cell surface and therefore, is accessible to antibodies, using the recognition capability of this antibiotic resistance marker.Objective: To determine the prevalence of yeast species in the evolution of patients with breast cancer treated with antiestrogen therapy. Materials & Methods: 30 postmenopausal patients who attended the Southern OMI Medical Center were included. The following groups were formed: Group 1 patients diagnosed with Breast Ca. treated with anti estrogens for less than one year Group 2 patients diagnosed with Breast Ca. treated with anti estrogen for 1-2 years Group 3 patients diagnosed with Breast Ca. treated with anti estrogen for 2-5 years Group 4 patients diagnosed with Breast Ca., who have completed their treatment with anti estrogen. Patients were surveyed about their symptoms, periodontal indices and then oral mucosa sample were taken. Conventional Microbiological examinations for Candida species as well as the molecular biology study data were performed. Results: Microbiological findings showed that a greater variety of species of Candida were isolated from patients who used the drug during the first two years (Group 1 and 2). Only 2 species were isolated in patients who used the drug more than two years (Group 3) and those who have completed treatment (Group 4). Conclusion: The length of intake of anti estrogens influences the growth and species of Candida, having a cumulative beneficial effect on the population studied.C clariflavum is an anaerobic, cellulosome-forming thermophile, containing in its genome, a large number of cellulosomal enzymes and a complex scaffolding system. The major cohesin-dockerin interactions of the cellulosome components were characterized, and on this basis a model of diverse cellulosome assemblies was derived. Further on, we cultivated C. clariflavum on cellobiose-, microcrystalline celluloseand switchgrass-containing media, and isolated cell-free cellulosome complexes from each culture. Gel-filtration separation of the cellulosome samples revealed two major fractions, which were analyzed by label-free LC-MS/MS in order to identify the key players of the cellulosome assemblies therein. From the 13 scaffoldins present in C. clariflavum genome, 11 were identified, and a variety of enzymes from different glycoside hydrolase and carbohydrate esterase families were identified, including glycoside hydrolase families GH48, GH9, GH5, GH30, GH11 and GH10. The expression level of the cellulosomal proteins varied as a function of the carbon source used for cultivation of the bacterium. In addition, the catalytic activity of each cellulosome was examined on different cellulosic substrates, xylan and switchgrass. The cellulosome isolated from the microcrystalline cellulose-containing medium was the most active of all the cellulosomes that were tested. The results suggest that the expression of the cellulosome proteins is regulated by the type of substrate in the growth medium. Moreover, both cell-free and cell-bound cellulosome complexes were produced which can together degrade the substrate in a synergistic manner. These observations are compatible with our proposed model of cellulosome assemblies based on in-vitro cohesin-dockerin interactions studies in this bacterium.W on discovery of novel probiotic candidates are under running. Commercially, having access to a probiotic that already has industrial functionality in addition to good viability during of food processing and shelf life of product is always advantages. Few studies have been reported regarding probiotic properties of Streptococcus thermophilus strains although this species hugely used as starter culture in the production of yogurt and other dairy products. In this study, 12 isolates of S. thermophilus, that were previously isolated from home-made dairy products, were evaluated with regard to resistance to artificial gastric (pH 2.5 containing pepsin) and intestinal (pH 8.0 containing bile and pancreatin) juices, adherence ability to Caco-2 and HT29-MTX-E12 cell lines, hydrophobicity, resistance to antibiotics, and epithelial barrier function (transepithelial electrical resistance (TER) measurement). Although it has been generally assumed that S. thermophilus strains are not resistant to stresses induces in the GIT, the results of this study revealed that susceptibility of almost all of the tested strains to simulated gastric and intestine conditions was significantly lower than for probiotic control strain L. rhamnosus GG under both simulated gastric and intestinal conditions. Regarding to adherence efficiency to human gut epithelium cell lines, the results showed 7 and 6 out of 12 isolates exhibited significantly superior adherence to Caco-2 and HT29-MTX-E12 than control probiotic L. rhamnosus GG, respectively. TER measurement showed that 3 strains were able to protect Caco-2’s tight junction. Although further investigations are necessary, our results identified some of the S. thermophilus strains as probiotic candidates worth further analysis.Objective: Resistance to antibiotics by Extended Spectrum Beta-lactamases (ESBLs) producing clinically significant bacterial strains has continuously been emerging and is a great threat to therapeutics. SHV and TEM derived ESBLs producing Enterobacteriaceae have been reported throughout the world but there is a limited data available for the molecular characterization of these enzymes in Pakistan.H foot and mouth disease (HFMD) is commonly caused by a group of Enteroviruses such as Enterovirus 71(EV71) and Coxsackievirus CVA5, CVA8 and CVA 16. Coxsackieviruses generally cause mild symptoms such as high fever, rashes and vesicles in the hand, foot and mouth but EV71 can produce more severe symptoms such as brainstem encephalitis, leading to cardiopulmonary failure and death. China experienced over 2.7 million cases of HFMD infections with 384 deaths in 2014. The lack of vaccines and antiviral drugs against EV71 highlights the urgency of developing preventative and treatment agents against EV71 to prevent further fatalities. The inactivated vaccine (IV) is well advanced in development and has good clinical trial data to support the use of the vaccine. It is ready for production in China but it remains to be investigated if the immunogenicity of the IV is able to confer protection against all EV71 sub-genotypes. Although there is data to support broad protection for some genotypes/sub-genotypes at varying efficacies, more studies need to be carried out on whether the neutralizing levels induced by IV are sufficient to protect against serious HFMD infections. New developments of experimental vaccines and antivirals are presented.