Michael Surette

The way that DNA encodes the instructions for proteins is through a set of four molecules called bases, each of which represents a letter of the genetic code (A = adenine, C = cytosine, G = guanine, and T = thymine). The bases are made of carbon and nitrogen rings and are bound to a sugar and a phosphate to form a nucleotideThe nucleotides are connected together to form a long chain with the bases pointing out.

When you're studying microbiology, you need to know the key differences between the three domains of life, how scientists name and classify organisms, and how scientists identify microorganisms.Differences among bacteria, archaea, and eukaryotic microorganismsThere are three domains of life: bacteria (also known as eubacteria), archaea, and eukarya.

Prokaryotic cells come in many different shapes and sizes that you can see under a microscope. A description of the shape of a cell is called the cell morphology. The most common cell morphologies are cocci (spherical) and bacilli (rods).Coccibacillus are a mix of both, while vibrio are shaped like a comma, spirilla are shaped like a helix (a spiral, sort of like a stretched-out Slinky), and spirochetes are twisted like a screw.

Catabolism (the breakdown of compounds for energy conservation) can happen in different ways for different types of microorganisms. In chemoorganotrophs (organisms that derive their energy from organic compounds), there are two forms of catabolic metabolism: fermentation and respiration. Fermentation is a form of anaerobic catabolism (in the absence of O2) where the organic substrate acts as both the electron donor and the electron acceptor.

If you imagine the microbial cell as a small factory, then the enzymes are the robots doing all the work. Enzymes are special proteins that are very good at converting things from one form to another. They do this by kicking off the chemical reactions needed for the conversion. The kinds of enzymes a microbe makes determine what type of metabolism the microbe will use to harness energy and grow.

Perhaps one of the most frightening and nastiest of the microbes may be the ones people don’t know about and can’t prepare for. Organizations like the World Health Organization and the U.S. Centers for Disease Control are constantly on the alert for new emerging pathogens, yet these pathogens can still appear without warning.

The breakdown of compounds by respiration releases much more energy than does the breakdown of the same compounds by fermentation. This is because the complete reduction of the products of fermentation isn’t possible without oxygen or oxygen substitutes to act as terminal electron acceptors. The star of this phenomenon is the electron transport chain, which involves several electron acceptors positioned within a membrane in order of reducing power so that the weakest electron acceptors are at one end of the chain and the strongest electron acceptors are at the other end.

Since the beginning of their widespread use in 1943, antibiotics have saved countless lives and changed the way medicine is practiced. Before their discovery, people suffered or died from infectious diseases that today are a mere annoyance, like sexually transmitted diseases and post-operative infections. Today antibiotics are essential in treating life-threatening bacterial infections, like pneumonia and sepsis, and are used preventively in a number of medical procedures (like surgery) and treatments (like cystic fibrosis).