ABSTRACT
Aims: This study aims to describe the biochemical and kinetic properties of a dehalogenase produced by a bacterium, Bacillus cereus WH2 (KU721999), that is uniquely adept at degrading a β-haloalkanoic acid, i.e., 3-chloropropionic acid (3-CP), and using it as the bacterium’s sole carbon source. The bacterium was isolated from abandoned agricultural land in Universiti Teknologi Malaysia that was previously exposed to herbicides and pesticides. Methodology and results: The B. cereus impressively removed 97% of 3-CP after 36 h of culturing. The intracellular WH2 dehalogenase of the bacterium was purified 2.5-fold and has an estimated molecular mass of 37 kDa. The highest activity of the dehalogenase was achieved under conditions of 30 °C and pH 7. The metal ions Hg2+ and Ag2+ substantially repressed the enzyme’s activity, but the enzyme’s activity was uninhibited by dithiothreitol (DTT) and EDTA. The WH2 dehalogenase showed a higher affinity for 3-CP (Km = 0.32 mM, kcat = 5.74 s-1 ) than for 3-chlorobutyric acid (3-CB) (Km = 0.52 mM; kcat = 5.60 s-1 ). The enzyme was ~1.6-fold more catalytically efficient (kcat/Km) in dehalogenating the three-carbon substrate 3-CP (17.8 mM-1 s -1 ) than the four-carbon 3-CB (11.2 mM-1 s -1 ). Conclusion, significance and impact of study: The novel B. cereus bacterium isolated in this study may prove applicable as a bioremediation agent to cleaning environments that are polluted with β-halogenated compounds. Furthermore, such an approach to treat polluted environments is more sustainable and potentially safer than chemical treatments.
ABSTRACT
Friedreich ataxia [FRDA] is an autosomal recessive disorder caused by guanine-adenine-adenine [GAA] triplet expansions in the FXN gene. Its product, frataxin, which severely reduces in FRDA patients, leads to oxidative damage in mitochondria. The purpose of this study was to evaluate the triple nucleotide repeated expansions in Iranian FRDA patients and to elucidate distinguishable FRDA clinical differences in these patients. A number of 22 Iranian patients [8 females and 14 males] from 16 unrelated families were studied. DNA was extracted from the peripheral blood of patients. The frequency and length of [GAA]n repeats in intron 1 of the FXN gene were analyzed using long-range PCR. In this study, the clinical criteria of FRDA in our patients and the variability in their clinical signs were also demonstrated. An inverse relationship was observed between GAA repeat size and the age of onset. Although some distinguishable clinical features [such as limb ataxia and lower limb areflexia] were found in our patients, 90-95% of them had extensor plantar response and dysarthria. The results showed only one positive diabetes patient and also different effects on eye movement abnormality among our patients. The onset age of symptoms showed a significant inverse correlation with allele size in our patients [P>0.05]. Based on comparisons of the clinical data of all patients, clinical presentation of FRDA in Iranian patients did not differ significantly from other FRDA patients previously reported