Enzyme Breaks Down Hydrocarbons

black and white microscopic image of bacteria

Biological Strategy

Mycobacterium

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Image: Anna Irini Koukkou / Research Gate / Some rights reserved

Chemically Break Down Organic Compounds

The vast majority of biochemical assembly and breakdown processes–even by the most complex organisms–occur within cells. In fact, cells are able to perform hundreds, even thousands of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). Part of the reason that decomposition reactions (chemical breakdown) can occur under such mild conditions is because most often, they occur in a stepwise, enzyme-mediated fashion, sipping or releasing small amounts of energy at each step. For example, the breakdown of glucose to pyruvate–and the release of energy–occurs in the 10-step enzyme catalyzed process of glycolysis.

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Bacteria

Domain Bacteria (“small staff”): L. acidophilus, Staphylococcus

From inside of our own bodies to the deepest parts of the ocean, bacteria have adapted to almost every possible environment. All bacteria are unicellular, microscopic, and lack a membrane-bound nucleus and organelles, and come in three basic shapes: spherical (cocci), rod (bacilli), and spiral (spirilla). Some strains can be deadly, like Staphylococcus aureus (MRSA) while others, like Lactobacillus acidophilus, found in our intestinal microbiome, keep us healthy. Cyanobacteria, also known as blue green algae, caused the Great Oxidation Event 2.4 billion years ago, producing Earth’s first oxygenated atmosphere.

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The metabolism of Mycobacterium gilvum can break down polycyclic aromatic hydrocarbons, including pyrene, via the dioxygenase NidAB enzyme.

“Mycobacterium gilvum (previously referred to as Mycobacterium flavescens strain PYR-GCK) has been isolated in the sediment from the Grand Calumet River in Indiana as a strain capable of using pyrene as a sole source of carbon and energy. This strain was also capable of metabolizing such polycyclic aromatic hydrocarbons (PAHs) as phenanthrene and fluoranthene, but not naphthalene, chrysene, anthracene, fluorene, or benzo[a]pyrene (Dean-Ross and Cerniglia, 1996). The first step of pyrene degradation is catalysed by the same two-subunit aromatic ring-hydroxylating dioxygenase NidAB as the one found in Mycobacterium vanbaalenii and other PAH-degrading mycobacteria (Brezna et al., 2003). Thus, M. gilvum probably differs from them in the downstream steps of PAH degradation, which now could be deduced through genome comparisons.” (Galperin 2007:1871-1872)

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