| Summary: | Halogenated compounds are extensively utilized in different industrial applications such as pesticides and herbicides and cause severe environmental problems because of their toxicity and persistence. Degradation of these compounds by the biological methodis a significant method to reduce these recalcitrant. Mesorhizobium lotiis im-portant for nitrogen fixation in legume roots.Up to now, there is no report to indicate M.loti can produce dehalogenase enzymes. Thus,a total of twenty-five genomes ofM.lotistrains from the National Center for Biotechnology Information (NCBI) were an-alyzed. These strains notably carrydehalogenase genes and were further investigated. The relative ratio ofhaloalkane and haloacid dehalogenase type II orL-type from all twenty-five genomes was 26% and 74%, respectively, suggesting type II dehalogen-ase is common. Surprisingly, only M.lotistrain TONO carries four dehalogenases and therefore it was further characterized. The chromosome of M.lotistrain TONO con-tains four haloacid dehalogenase type II genes namely, dehLt1(MLTONO_2099),dehLt2(MLTONO_3660), dehLt3(MLTONO_4143), anddehLt4(MLTONO_6945), and their corresponding enzymes were designated as DehLt1, DehLt2, DehLt3, and DehLt4, respectively. The only haloalkane dehalogen-ase gene (MLTONO_4828) was located upstream of thedehLt3gene and its amino acid share 88% identity with DmlA of Mesorhizobium japonicumMAFF 303099. The putative haloacid permease gene designated asdehrPt(MLTONO_0284) was located downstream of thedehLt1and its amino acids show 69% identity with haloacid per-mease ofRhizobiumsp. RC1. The gene encoding helix-turn-helix (HTH) motif family DNA-binding protein regulator and LysR family transcriptional regulator genes were also identified, possibly for regulatory functions. The genomic studies as such, have good potential to be screened for new type of dehalogenases based on basic molecular structure and functions analysis
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