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Haloaklophilic bacteria have a potential advantage as a bioremediation organism for high pH oil polluted and industrial wastewater. In the current study, Haloalkaliphilic isolates were obtained from Hamralake, Wadi EL-Natrun, Egypt. The phenotypic features, biochemical characters, and 16S rRNA sequence comparison were used to identify the bacterial isolates including Halomonas HA1 and Marinobacter HA2. These strains showed high requirement of NaCl for growth specially HA1 strain that essentially required NaCl for its growth. The isolates are capable of degrading phenol at optimal pH values between 8 and 9 with the ability to grow in levels of pH up to 11, like what was seen in Halomonas HA1 strain. Both isolates represent two different mechanistic pathways for phenol degradation. Halomonas HA1 exploits the 1,2 phenol meta cleavage pathway while Marinobacter HA2 using the 2,3 ortho cleavage pathway indicated by universal primer sets for 1,2 and 2,3 CTD genes. Phenol degradation showed a comparable pattern between both isolates, while Marinobacter HA2 isolate can eliminate the added phenol within an incubation period of 72 h, The Halomonas HA1isolate required 96 h to degrade 84% of the same amount of phenol. The phylogenetic analysis of the amino acid sequence of 1,2 CTD (catechol dioxygenase) of Halomonas HA1showed an evolutionary relationship between 1,2 dioxygenases of both Halomonadaceae and Pseudomonadaceae while 2,3 CTD of Marinobacter HA2 shared the main domains of the closely related species. Semi-quantitative RT PCR analysis proved the constitutive expression pattern of both dioxygenase genes. |
