TITLE:
Cellular Localization of Gold and Mechanisms of Gold Resistance in Rhodobacter sphaeroides
AUTHORS:
Hannah Johnson, Ram C. Kafle, Madhusudan Choudhary
KEYWORDS:
Rhodobacter sphaeroides, Heavy Metal Bioremediation, Inductively Coupled Plasma (ICP), Transmission Electron Microscopy (TEM)
JOURNAL NAME:
Advances in Microbiology,
Vol.7 No.8,
August
7,
2017
ABSTRACT: Heavy metal pollution is a worldwide problem with many associated health risks, including bone loss, kidney damage, and several forms of cancer. There is a great need of bioremediation of these toxic metals from the environment, as well as implementing a monitoring system to control the spreading pollution. This study focuses on the bioremediation potential of Rhodobacter sphaeroides in the presence of the toxic gold chloride (AuCl3). Growth characteristics of the bacterial cells exposed to a range of toxic gold concentrations were analyzed through the growth kinetics and the colony forming units under aerobic, photosynthetic, and anaerobic growth conditions. The localization of the gold particles within two cellular fractions, cytoplasm and the plasma membrane, are analyzed using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Results of this study demonstrated the photosynthetic growth condition as best suited for the metal tolerance, compared to the aerobic and anaerobic growth conditions. Results also revealed the overall accumulation and localization of gold particles, while not different between the membrane and the cytoplasmic fractions increased at different concentrations of the gold contamination. The results of the localization under photosynthetic growth condition revealed the accumulation reached the highest very quickly, and an overall shift in localization of the gold particles from an equal distribution to an increase within the membrane fraction at the highest concentrations of gold contamination. The localization of the gold particles was validated by Transmission Electron Microscopy (TEM) where the results confirmed the increase in accumulation within the membrane, and photosynthetic membranes, of R. sphaeroides.