Fermentation and Oxidation-Reduction Reactions Overview

Cellular Reactions

• Fermentation reactions produce little energy (~ 2 ATP molecules)
• Oxidation-reduction reactions: paired reactions where electrons are transferred from one compound to another
  • Oxidation: loss of one or more electrons by a molecule
  • Reduction: gain of one or more electrons by a molecule
• Dehydrogenation reactions: many biological oxidations involve the removal of hydrogen ions and electrons
• Anabolic reactions: require energy to form chemical bonds, often obtained through catabolic reactions
• Photosynthetic reactions: trap light energy and convert it into chemical bond energy in ATP and carbohydrates (e.g., glucose)

Genetics

• Genetics: the study of heredity
• Genotype: an organism's complete collection of genes
• Phenotype: an organism's physical traits resulting from its genotype
• Genes: direct all cellular functions and are made up of specific segments of chromosomes
• Mutation: a change in a DNA molecule that is transmissible to offspring
• Ways bacteria acquire new genetic information:
  • Lysogenic conversion
  • Transduction
  • Transformation
  • Conjugation

Lysogenic Conversion

• Temperate phages (lysogenic phages) inject their DNA into bacterial cells
• Phage DNA integrates into the bacterial chromosome, but does not cause the lytic cycle
• Prophage: phage DNA that remains in the bacterial cell
• Lysogenic cell: the bacterial cell containing the prophage

Transduction

• Involves bacteriophages carrying bacterial genetic material from one cell to another
• Only small amounts of genetic material are transferred
• Differs from lysogenic conversion, which involves viral genes

Transformation

• A bacterial cell becomes genetically transformed following the uptake of DNA fragments ("naked DNA") from its environment
• Competence: the ability to absorb naked DNA into the cell
• Only occurs in certain bacteria

Conjugation

• Involves the transfer of genetic material (usually a plasmid) from a donor cell to a recipient cell through a specialized type of pilus (sex pilus)
• Plasmids: extrachromosomal DNA molecules that can exist independently or integrate into the chromosome
• Resistance factors (R-factors): plasmids containing multiple genes for antibiotic resistance

Genetic Engineering

• Involves techniques to transfer eukaryotic genes (e.g., human genes) into easily cultured cells to manufacture important gene products (e.g., proteins)
• Plasmids are frequently used as vehicles for inserting genes into cells

Microbial Growth

• Availability of nutrients affects microbial growth
• Symbiotic relationships:
  • Mutualism: beneficial to both organisms (e.g., lichens, human-E. coli relationship)
  • Parasitism: beneficial to one organism (the parasite) and detrimental to the other (the host)
• Indigenous microflora: the microorganisms naturally present on and within humans
• Transient microflora: microorganisms that take up temporary residence on and within humans

Epidemiologic Terminology

• Communicable disease: an infectious disease that can be transmitted from one person to another
• Contagious disease: a communicable disease that is easily transmitted from person-to-person
• Incidence: the number of new cases of a disease in a defined population during a specific time period
• Morbidity rate: the number of new cases of a disease per a specifically defined population
• Prevalence: the number of cases of a disease existing in a given population during a specific time period
• Sporadic disease: a disease that occurs only occasionally within a population
• Endemic disease: a disease that is always present within a population

Beneficial and Harmful Roles of Indigenous Microflora

• Humans derive many benefits from their indigenous microflora (e.g., vitamins K and B12)
• Microbial antagonism: many members of the indigenous microflora prevent other microbes from becoming established
• Opportunistic pathogens: microorganisms that "hang around" waiting for the opportunity to cause infection