Search

Occurrence of mineral forming and other bacteria in mats is well demonstrated. However, their high diversity shown by ribotyping has not been explained, although it could explain the diversity of formed minerals. Common biomarkers as well as phylogenic relationships are useful tools for clustering the isolates and the prediction of their potential role in the natural niche. In this study, a combination of MALDI-TOF MS with PCA was shown to be a powerful tool to categorize 35 mineral forming bacterial isolates isolated from Dohat Faishakh sabkha, northwest of Qatar (23 from decaying mats and 12 from living ones). The 23 strains from decaying mats belong to the Virgibacillus genus as identified by ribotyping and are shown to be highly involved in the formation of protodolomite and a diversity of minerals. They were used as internal references for the categorization of sabkha bacteria. Combination of the isolation of bacteria on selective mineral forming media, their MALDI TOF MS protein profiling and PCA analysis established their relationship in a phylloproteomic dendrogram based on protein biomarkers including m/z 4905, 3265, 5240, 6430, 7765, and 9815. PCA analysis clustered the studied isolates into 3 major clusters, showing strong correspondence to the 3 phylloproteomic groups that were established by the dendrogram. Both clustering analysis means have evidently demonstrated a relationship between known Virgibacillus strains and other related bacteria based on profiling of their synthesized proteins. Thus, larger populations of bacteria in mats can be easily screened for their potential to exhibit certain activities, which is of ecological, environmental and biotechnological significance. This work was made possible by the QUST-1-CAS-2018-3 fund, a student grant from the Qatar University. Many thanks to Microbiology laboratory, Hamad Medical Corporation for providing facility for MALDI-TOF MS technique. The statements made herein are solely the responsibility of the authors. Scopus

Reverse Osmosis (RO) is a promising environment friendly desalination technology for clean water production. However, the performance of RO is getting affected by the mineral scaling and biofouling. During this research, various unknown interactions occurring in RO systems between minerals, microorganisms, antiscalants and antimicrobial nanomaterials were investigated. The first goal of this dissertation was to understand and investigate the calcium sulfate scaling on reverse osmosis membranes in terms of effect of different concentrations of calcium ions and effect of temperature of feedwaterfeed water. It was noted that the mineral scaling tends to increase with the increase in temperature and concentration of ions. Moreover, the results showed that the functional groups of membranes such as hydroxyl and carboxyl, tend to interact with gypsum during scaling. To investigate the interaction of seawater microorganisms with antiscalants and with calcium sulfate, various bacterial strains were isolated and identified from Gulf seawater. The identification results showed that the isolated bacteria include Halomonas aquamarina, Pseudomonas fragi, Pseudomonas stutzeri and others. It was noted that the bacterial strains have the capability to utilize antiscalants as a carbon and energy source, thereby, degrading them and making them ineffective against scaling. Moreover, the isolated bacterial strains were also found to be capable of mediating/inducing calcium sulfate precipitation on RO membranes. The results of these interactions showed that microorganisms may enhance mineral scaling via (i) biodegradation of antiscalants and (ii) biomineralization of calcium sulfate. Therefore, it is important to modify RO membranes to tackle both mineral scaling and biofouling, simultaneously. In this research, the polyamide RO membranes were modified with antimicrobial nanomaterial (graphene oxide) and polymer antiscalants to improve the surface characteristics of RO membranes and to give rise to antifouling characteristics in membranes. The results showed that the newly modified membranes have the capability to control calcium sulfate scaling. In addition, the antibiofouling tests performed through determining bacteriostasis rates also showed that the modified membranes inhibited the growth of bacteria. Overall, the results of this research provided in-depth information about various interactions occurring in RO systems and demonstrated the potential of membrane modification technique to control various types of membrane fouling, simultaneously