Jennifer Stearns

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.

There are many professions where knowing about microbes, either pathogenic or benign, is handy. There are also plenty of situations where applying a microbiology approach to a problem will get you out of a jam. Some are industries that employ microbiologists, and others are situations where a knowledge of microbiology is essential to getting the job done.

The habitat is an important concept in biology and microbiology in particular because microorganisms are greatly affected by where they live. Microbial habitats — including soils, rivers, lakes, oceans, on the surface of living and dead things, inside other organisms, on man-made structures, and everything in between — provide nutrients and protect cells from harsh conditions.

Cells are able to take up nutrients from the environment thanks to membrane-spanning transporter proteins. Different types of transporters are required to transport the wide range of nutrients that cells need, but this often comes at an energy cost because the cell must build up internal stores at higher concentrations than those found in the environment.

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.

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.