Abstract
Thiols play very important role in the intracellular redox homeostasis. Imbalance in the redox status leads to changes in the intracellular metabolism including respiration. Thiol stress, a reductive type of stress can also cause redox imbalance. When Gram-positive bacterium Strep- tomyces coelicolor was exposed to thiol stress, catalaseA was induced. Induction of catalaseA is the consequence of elevation of ROS (reactive oxygen species). The two major sources of reactive oxygen species are Fenton reaction and slippage of electrons from electron transport chain during respiration. Hence, the effect of thiol stress was checked on the rate of oxidative phosphorylation in S. coelicolor. We found correlation in the increase of oxidative phosphorylation rate and the generation of ROS, subsequently leading to induction of catalase. It was observed that thiol stress does not affect the functionality of the individual complexes of the ETC, but still there was an increase in the overall respiration, which may lead to generation of more ROS leading to induction of catalase.
Highlights
According to endosymbiont hypothesis mitochondria evolved from the primitive aerobic bacteria [1]
In the present work we studied the effect of DTT stress on oxidative phosphorylation, its correlation with reactive oxygen species (ROS) generation and subsequently catalaseA induction in the bacterium Streptomyces coelicolor
Oxygen uptake signal in bacteria was in compliance with that of the mitochondria, but the ADP/O ratio was found to be slightly lower in the presence of all the four substrates
Summary
According to endosymbiont hypothesis mitochondria evolved from the primitive aerobic bacteria [1]. Bacteria have their electron transport chain located on the inner membrane. There is a lot of flexibility in bacterial electron transport and it varies amongst different bacteria and shows changes in response to growth conditions. Bacteria generally possess a branched electron transport chain with features, which equip bacteria for successful adaptation to changes in the environment [2,3]. Based on the physiology and environment of the bacteria, many organic and inorganic molecules such as nitrate and fumarate, can act as terminal electron acceptors instead of oxygen, facilitating anaerobic growth [4,5]. The efficiency of oxidative phosphorylation is higher in intact mitochondria as compared to that of bacteria. Overall bacterial oxidative phosphorylation rate is lower than that of intact mitochondria in oxidizing the identical substrates [6,7]
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