16S rRNA characterization of a Bacillus isolate and its tolerance profile after subsequent subculturing [electronic resource].

Includes references.

The isolation of microorganisms from different highly contaminated environments offers novel bacteria of unique functionality and potential applications in different biotechnological processes. It also entails a variety of genes responsible for microbial tolerance or defense against extreme conditions or xenobiotics present in the media. In a previous work, Bacillus spp. isolated from textile wastewater was exploited in terms of characterization, tolerance to pH, salinity, cold temperature and hydrogen peroxide, and the mechanism of resistance against hydrogen peroxide (Gomaa and Momtaz, 2006). This isolate was phenotypically identified as Bacillus maroccanus/Bacillus simplex. In this study, the primary aim was to characterize this strain using 16S rRNA partial gene amplification and sequencing. It was assigned as Bacillus simplex TWW-04. DNA-DNA hybridization showed 96% relatedness to Acinetobacter. The tolerance profile of this strain was examined in regard to the four traits previously mentioned. A 36-month subculturing of this strain showed no change in tolerance to pH, salinity and cold temperature, whereas the tolerance to hydrogen peroxide was lost. A sample, frozen for the same duration, showed no change in any of the tested traits. The tolerance alleviation was evident after 24 months of subculturing. Testing the KatA gene responsible for hydrogen peroxide tolerance in the two samples showed higher band intensity in the frozen sample when compared to the subcultured sample. This indicates that the hydrogen peroxide tolerance trait is extrachromosomal and has been lost during successive cell division, while the other traits are chromosomal. Genbank/NCBI/accession number for this 16S rRNA strain EF025542.

Summary in Arabic.

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