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To overcome the partial or complete failure of oil hydrocarbon bioremediation due to weathering processes, occurring in most oil producing and spilling areas, nutritional requirements of the most widely used bacterium, Pseudomonas aeruginosa, were shown to be necessary to predict in advance, because they affect its activity to remove categories of polluting hydrocarbons. This study showed a high diversity of the relationship between the metabolism and the biological activity of Pseudomonas aeruginosa. The Gulf area represents a good site to isolate three highly adapted Pseudomonas aeruginosa strains from different highly polluted and weathered soils. The close relationship between the bacterial strains and the micro environment composition was investigated. Statistical analysis, using 23 factorial design, of the correlation between nutritional requirements of three Pseudomonas aeruginosa strains and their potential to degrade diesel hydrocarbons was carried-out. Long term adaptation of hydrocarbon-degrading bacteria to weathered hydrocarbons and harsh conditions provides them with specific metabolic potentialities that vary from one isolate to another although belonging to the same species. The sensitivity of hydrocarbon-degrading bacterial growth and the biological activity of the three isolates were analyzed. The optimal media composition in term of carbon, nitrogen and phosphorous concentrations related to their C/N/P ratios varied among the isolates with a maximal biomass production reaching 90 × 107 CFU ml−1. The significance of the first and second order interactions of C, N and P sources showed high variability in the impact on growth and biological activity. Hydrocarbon removal was much higher for high molecular weight ones, reaching almost 90% for strains under specific growth conditions for each isolate. This is of high importance for remediating weathered oil. Mostly, all strains expressed enhanced removal activity by the second week of incubation. However, removal and conversion of diesel hydrocarbons was found to be highly sensitive to the availability and balance of the nutrients and varied from one Pseudomonas aeruginosa strain to another. This is of great importance from the practical point of view for spilled oil bioremediation using Pseudomonas aeruginosa. Other information Published in: RSC Advances License: https://creativecommons.org/licenses/by-nc/3.0 See article on publisher's website: http://dx.doi.org/10.1039/c7ra04704e

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

Studies have demonstrated that microbes facilitate the incorporation of Mg into carbonate minerals, leading to the formation of potential dolomite precursors. Most microbes that are capable of mediating Mg-rich carbonates have been isolated from evaporitic environments in which temperature and salinity are higher than those of average marine environments. However, how such physicochemical factors affect and concur with microbial activity influencing mineral precipitation remains poorly constrained. Here, we report the results of laboratory precipitation experiments using two mineral-forming Virgibacillus strains and one non-mineral-forming strain of Bacillus licheniformis, all isolated from the Dohat Faishakh sabkha in Qatar. They were grown under different combinations of temperature (20°, 30°, 40 °C), salinity (3.5, 7.5, 10 NaCl %w/v), and Mg:Ca ratios (1:1, 6:1 and 12:1). Our results show that the incorporation of Mg into the carbonate minerals is significantly affected by all of the three tested factors. With a Mg:Ca ratio of 1, no Mg-rich carbonates formed during the experiments. With a Mg:Ca ratios of 6 and 12, multivariate analysis indicates that temperature has the highest impact followed by salinity and Mg:Ca ratio. The outcome of this study suggests that warm and saline environments are particularly favourable for microbially mediated formation of Mg-rich carbonates and provides new insight for interpreting ancient dolomite formations.

To overcome the partial or complete failure of oil hydrocarbon bioremediation due to weathering processes, occurring in most oil producing and spilling areas, nutritional requirements of the most widely used bacterium, Pseudomonas aeruginosa, were shown to be necessary to predict in advance, because they affect its activity to remove categories of polluting hydrocarbons. This study showed a high diversity of the relationship between the metabolism and the biological activity of Pseudomonas aeruginosa. The Gulf area represents a good site to isolate three highly adapted Pseudomonas aeruginosa strains from different highly polluted and weathered soils. The close relationship between the bacterial strains and the micro environment composition was investigated. Statistical analysis, using 23 factorial design, of the correlation between nutritional requirements of three Pseudomonas aeruginosa strains and their potential to degrade diesel hydrocarbons was carried-out. Long term adaptation of hydrocarbon-degrading bacteria to weathered hydrocarbons and harsh conditions provides them with specific metabolic potentialities that vary from one isolate to another although belonging to the same species. The sensitivity of hydrocarbon-degrading bacterial growth and the biological activity of the three isolates were analyzed. The optimal media composition in term of carbon, nitrogen and phosphorous concentrations related to their C/N/P ratios varied among the isolates with a maximal biomass production reaching 90 × 107 CFU ml-1. The significance of the first and second order interactions of C, N and P sources showed high variability in the impact on growth and biological activity. Hydrocarbon removal was much higher for high molecular weight ones, reaching almost 90% for strains under specific growth conditions for each isolate. This is of high importance for remediating weathered oil. Mostly, all strains expressed enhanced removal activity by the second week of incubation. However, removal and conversion of diesel hydrocarbons was found to be highly sensitive to the availability and balance of the nutrients and varied from one Pseudomonas aeruginosa strain to another. This is of great importance from the practical point of view for spilled oil bioremediation using Pseudomonas aeruginosa.

Pollution, due to activities related to the oil industry, represents a serious threat to the natural environment. The application of biotechnological methods provides much safer and sustainable alternatives for bioremediation of polluted areas, using microorganisms. Several techniques for the isolation of hydrocarbon degrading bacteria have been investigated and published worldwide. A wide range of bilogical activities was shown. However, local hydrocarbon degrading strains and the factors affecting bacterial and strains variability were not studied deeply. In this study, we showed that the isolation and screening strategy affected a lot, the selection of the strains. We combined the bacterial tolerance to hydrocarbon toxicity, assessed by the growth parameters, and the bacterial degradative activities, assessed by the degradation of a wide range of petroleum hydrocarbons via Gas Chromatography analysis. The main investigations and findings of the present work are: -A collection of 39 bacterial isolates from the Qatari environment was set up and a new isolation and screening program was proposed. -The Growth conditions and the activity of pre-selected strains -Shift of the activity of the selected strains from a range of hydrocarbons to another by the effect of the nitrogen source, C/N ratio and organic nitrogen source -70% hydrocarbon removal, achieved with several strains in 2 weeks. -Amongst 12 identified isolates and by molecular ribotyping-DNA sequencing, 3 Pseudomonas strains isolated from a polluted area in Qatar, are available for bioremediation of highly polluted soils, tolerating high toxicity and may be adapted to a variety of low or high molecular weight hydrocarbons.