Microbiology Basics

Metabolism and Energy

• Chemical reactions within cells are essential for all living things and involve energy needs and building cellular structures.
• Energy sources include chemicals, light, and inorganic and organic compounds.

Nutrients and Elements

• Nutrients are chemicals used by organisms to meet energy needs and build cellular structures.
• Carbon is an essential element for microbial growth and reproduction.
• Hydrogen is a common element in cells essential for redox reactions and electron transfer.
• Phosphorus is essential for phospholipid membranes, DNA, and ATP.
• Sulfur is critical for disulfide bonds in proteins and some vitamins.
• Trace elements are required in very small amounts for growth.

Organisms and Classification

• Heterotrophs are organisms that catabolize organic molecules acquired from other organisms.
• Chemotrophs are organisms that acquire energy from redox reactions involving inorganic and organic chemicals.
• Phototrophs are organisms that use light as an energy source.
• Autotrophs are organisms that utilize an inorganic source of carbon (e.g., carbon dioxide) as their sole carbon source.
• Photoautotrophs use light as an energy source and carbon dioxide as a carbon source.
• Chemoautotrophs use inorganic chemicals as an energy source and carbon dioxide as a carbon source.
• Photoheterotrophs use light as an energy source and organic compounds as a carbon source.
• Chemoheterotrophs use organic compounds as both an energy and carbon source.
• Organotrophs acquire electrons from organic molecules.
• Lithotrophs utilize electrons from inorganic molecules.

Microbial Growth and Requirements

• Microbial growth requires consideration of chemical, physical, and energy needs.
• Anaerobes are organisms that grow without oxygen.
• Aerobes are organisms that require oxygen for growth.
• Facultative anaerobes are organisms that can grow with or without oxygen.
• Microaerophiles are organisms that require reduced levels of oxygen for growth.
• Obligate anaerobes are organisms lacking catalase and peroxidase, susceptible to hydrogen peroxide.

Oxygen Toxicity and Defense

• Oxygen toxicity refers to the harmful effects of singlet oxygen, superoxide radical, peroxide anion, and hydroxyl radical on organisms.
• Catalase and peroxidase are enzymes that detoxify hydrogen peroxide.
• Superoxide dismutases are enzymes that detoxify superoxide radicals in aerobic organisms.
• Antioxidants are substances that reduce toxic oxygen products.

Nitrogen Fixation and Biofuels

• Nitrogen fixation is the conversion of atmospheric nitrogen into ammonia by certain bacteria.
• Biofuels are fuels derived from metabolic activity converting sugars into ethanol or butanol.

Genetic Engineering and Cellulose

• Genetic engineering involves manipulating an organism's genes to express desired traits.
• Cellulose is a polymer of glucose composing the majority of plant cell wall material.
• Cellulases are enzymes that degrade cellulose into free sugars.