الفهرس 
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Abstract
Hammam Pharaon (Pharaoh’s Bath) is one of the most important hot springs in Egypt which has been not yet investigated in deep study from the microbiological point of view especially Thermophilic bacteria as hot springs considered to be the natural habitat of thermophilic and hyperthermophilic microorganisms with optimal growth temperatures of >55 °C and >80 °C.In this study, three local bacterial strains, named Geobacillus HM101, Rhodothermus HM102 and Thermus HM103 was isolated, purified and subsequently identified by 16S rRNA gene nucleotide sequence and analysis. Based on their 16S rRNA sequences, HM101were identified as Geobacillus sp which are most closely related to Geobacillus thermoglucosidasius (95% identity), HM102 were identified as Rhodothermus sp which are most closely related to Rhodothermus marinus (99.8% identity) and HM103 were identified as Thermus sp which were most closely related to Thermus thermophiles (99.2% identity). The obtained 16S rRNA sequences were submitted to the Genbank and assigned an accession numbers KU096044, KU096045 and KU096046 respectively.Analysis of total fatty acid composition of the three isolates resulted in the identification of 13 different fatty acids, careful analysis of the fatty acid profile of our local isolates revealed a surprising trend of the predominant; where, dodecanoic acid (12:0), undecanoic acid (11:0) and Decanoic acid (10:0) were represented by about 41, 20 and 17%, respectively. The dominance of these relatively short chain saturated fatty acid correlates well with the increased membrane fluidity to tolerate and survive at the high temperature (75̊°C) prevalent inside Hammam Pharaon spring. Although, the enzyme activities such as amylases derived from these isolates were discouraging, but their presence and thermotolerance can be employed for further studies. Additionally, the possibility to use these isolates or any of their enzymes in production and/or degradation of bioactive compounds either alone or in co-cultures would be a future direction and extension to this work. Central composite design (CCD) algorithm was set to detect the optimum pH and temperature for the growth of the three thermophilic isolate. In terms of interaction between temperature and pH, for isolate HM101 the optimum pH for growth was 6.45 and the optimum temperature was 70°C as shown in (Fig.4 a), for isolate HM102 the optimum pH for growth was 6.65 and the optimum temperature was 62°C as shown in (Fig.4 b), for isolate HM103 the optimum pH for growth was 7 and the optimum temperature was70°C.The present study is important in view of the documentation of the microbial diversity, thermophiles in particular, of Egyptian hot springs in Sinai region. Isolation and characterization of these strains is also a step toward conservation of these organisms where all the sequences have been accessioned by NCBI.