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Antimicrobial Activity of Bacillus Persicus 24-DSM Isolated From Dead Sea Mud

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Antimicrobial Activity of Bacillus Persicus 24-DSM Isolated From Dead Sea Mud

Nehaya Al-Karablieh. Open Microbiol J.

Abstract

Intorduction: Dead Sea is a hypersaline lake with 34% salinity, gains its name due to the absence of any living macroscopic creatures. Despite the extreme hypersaline environment, it is a unique ecosystem for various halophilic microorganisms adapted to this environment.

Aims & objectives: Halophilic microorganisms are known for various potential biotechnological applications, the purpose of the current research is isolation and screening of halophilic bacteria from Dead Sea mud for potential antimicrobial applications.

Methods & materials: Screening for antagonistic bacteria was conducted by bacterial isolation from Dead Sea mud samples and agar plate antagonistic assay. The potential antagonistic isolates were subjected to biochemical characterization and identification by 16S-rRNA sequencing. Among the collected isolates, four isolates showed potential antagonistic activity against Bacillus subtilis 6633 and Escherichia coli 8739. The most active isolate (24-DSM) was subjected for antagonistic activity and minimal inhibitory concentration against different gram positive and negative bacterial strains after cultivation in different salt concentration media. Results: The results of 16S-rRNA analysis revealed that 24-DSM is very closely related to Bacillus persicus strain B48, which was isolated from hypersaline lake in Iran.

Conclusion: Therefore, the isolate 24-DSM is assigned as a new strain of B. persicusi isolated from the Dead Sea mud. B. persicusi 24-DSM showed higher antimicrobial activity, when it was cultivated with saline medium, against all tested bacterial strains, where the most sensitive bacterial strain was Corynebacterium diphtheria 51696.

Keywords: Antagonistic assay; Antimicrobial activity; Bacillus persicusi; Corynebacterium diphtheria; Dead Sea mud; Inhibitory concentration.

Figures

Fig. (1)
Fig. (1)
Map of Dead Sea showing six sampling sites: A, B, C, D, E and F.
Fig. (2)
Fig. (2)
Phylogenetic tree of the Dead Sea mud isolates and their close relatives based on 16S-rRNA. The sequences were retrieved from NCBI database. The evolutionary distances were computed using the Maximum Composite Likelihood method [19] and evolutionary analyses were conducted in MEGA7 [18].
Fig. (3)
Fig. (3)
In vitro growth of 24-DSM in LB and MB medium at 37°C as determined by measurement of the OD600. Data represent the means of three independent cultures ± standard deviation.
Fig. (4)
Fig. (4)
Antagonistic assay against different bacterial strains by the 10X concentrated 24-DSM supernatants; as a representative samples A: Escherichia coli 6633, B: Corynebacterium diphtheria 51696. Bacterial strains suspension (100 µl of OD600 ~1.0) were spread on MHB agar medium, after drying, 10 µl of 10X concentrated 24-DSM supernatants were loaded in 4mm in diameters well (R1, R2 and R3), 10 µl of 12.5 mg/ml of chloramphenicol was used as positive control (Cm) and 10 µl of 10X desalted medium was used as a negative control (-ve).
Fig. (5)
Fig. (5)
Susceptibility of different bacterial strains to 10X concentrated 24-DSM supernatants by agar plate diffusion assay. Average of three replicates ± standard error. Bacterial strains suspension (100 µl of OD600 ~1.0) were spread on MHB agar medium, after drying, 10 µl of 10X concentrated 24-DSM supernatants were loaded in 4mm in diameters well. a,b: ANOVA and least significant differences at P = 0.05 using SPSS Statistics 21 for cultivation medium.

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