Reduction of chromium-VI by chromium-resistant Escherichia coli FACU: a prospective bacterium for bioremediation

• Published in: Folia microbiologica Vol. 65; no. 4; pp. 687 - 696
• Main Authors: Mohamed, Mahmoud S.M., El-Arabi, Nagwa I., El-Hussein, Ahmed, El-Maaty, Shereen Abu, Abdelhadi, Abdelhadi A.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-08-2020; Springer Nature B.V
• Subjects: Applied Microbiology; Biodegradation, Environmental; Biomedical and Life Sciences; Bioremediation; Carcinogens, Environmental - metabolism; Carcinogens, Environmental - pharmacology; Chromate reductase; Chromates; Chromium; Chromium - metabolism; Chromium - pharmacology; Coliforms; Drug Resistance, Bacterial; E coli; Environmental Engineering/Biotechnology; Escherichia coli; Escherichia coli - classification; Escherichia coli - isolation & purification; Escherichia coli - metabolism; Escherichia coli - physiology; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Hexavalent chromium; Immunology; Laser induced breakdown spectroscopy; Life Sciences; Line spectra; Microbiology; Mutagenicity; Original Article; Oxidation-Reduction; Oxidoreductases - genetics; Oxidoreductases - metabolism; Phylogeny; Qualitative analysis; Reductases; Reduction; RNA, Ribosomal, 16S - genetics; rRNA 16S; Soil Microbiology; Soil pollution; Species; Spectroscopy; Spectrum analysis; Toxicity; Trivalent chromium; Hexavalent chromium; Bioremediation; LIBS; Chromate reductase; E. coli
• ISSN: 0015-5632; 1874-9356
• DOI: 10.1007/s12223-020-00771-y

The release of hexavalent chromium [Cr (VI)] into environments has resulted in many undesirable interactions with biological systems for its toxic potential and mutagenicity. Chromate reduction via chromium reductase (ChrR) is a key strategy for detoxifying Cr (VI) to trivalent species of no toxicity. In this study, ten bacterial isolates were isolated from heavily polluted soils, with a strain assigned as FACU, being the most efficient one able to reduce Cr (VI). FACU was identified as
Escherichia coli
based on morphological and 16S rRNA sequence analyses. Growth parameters and enzymatic actions of FACU were tested under different experimental conditions, in the presence of toxic chromium species. The
E. coli
FACU was able to reduce chromate at 100 μg/mL conceivably by reducing Cr (VI) into the less harmful Cr (III). Two distinctive optical spectroscopic techniques have been employed throughout the study. Laser-induced breakdown spectroscopy (LIBS) was utilized as qualitative analysis to demonstrate the presence of chromium with the distinctive spectral lines for bacteria such as Ca, Fe, and Na. While UV-visible spectroscopy was incorporated to confirm the reduction capabilities of
E. coli
after comparing Cr (III) spectrum to that of bacterial product spectrum and they were found to be identical. The chromate reductase specific activity was 361.33 μmol/L of Cr (VI) per min per mg protein. The FACU (EMCC 2289) 16S rRNA sequence and the
ChrR
-partially isolated gene were submitted to the DDBJ under acc. # numbers LC177419 and LC179020, respectively. The results support that FACU is a promising source of ChrR capable of bioremediation of toxic chromium species.