Biology 318 Microbial Metabolism and Genetics

Energy Production • Phototrophs convert light to ATP energy • Chemotrophs convert chemicals to ATP energy • Lithotrophs use inorganic chemicals - S, N, Fe

Carbon Source

• Autotrophs use CO2 to make organic compounds • Heterotrophs use organic chemicals

ONLY some prokaryotes are lithotrophs.

Atmospheric Requirements

• Aerobic– use O2 – Obligate – Microaerophiles (5% O2) • Anaerobes– do not require O2 – Obligate – Aerotolerant – Facultative – Capnophiles (higher CO2) Chemoheterotrophic Microbial Reactions ES = electron source; EA = electron acceptor

Aerobic Example MANY body-associated microbes - like us Glucose (ES) + O2 (EA) yields CO2 + H2O

Anaerobic Example Other body-associated microbes - not like us Glucose (ES) + SO4 (EA) yields CO2 + H2S Basis for an important Salmonella ID test - LAB Chemolithotrophic Microbial Reactions ES = electron source; EA = electron acceptor

Aerobic Example Ammonia (ES) + O2 (EA) yields nitrate + H20 River pollution problem - creates acid, toxins

Anaerobic Example H2 (ES) + CO2 (EA) yields CH4 + H2O Methanogen - natural gas from decomposition Glycolysis

• Produce ATP without O2 • Net yield 2 ATP • Many organisms only use Fermentation

What It Really Means Means NOT using the Electron Transport Chain Chemoheterotrophs when O2 is absent

- Lactose or Sucrose to Lactic Acid Streptococcus - cavities, yogurt

- Starch to Glucose to Ethanol Yeast/Saccharomyces - beer, wine

Respiration

• Glucose converted to CO2 and water • Anaerobic respiration uses other compounds not O2 for electron acceptor Microbial Growth Spending of ATP to build cell parts for growth Growth - increase in the number of organisms Single bacterium multiplies to make a colony Bacterial Genetics and Evolution

Genotype and Phenotype Phenotype = physical traits Genotype = genetic make-up Phenotype determined by gene expression Bacterial genes on chromosome AND plasmids

Ways bacteria genetically evolve Mutations Lysogenic conversion Transduction Transformation Conjugation Mutations Naturally occur while copying DNA Rate - one mistake per million base pairs Mutagens enhance natural error rate e.g. chemicals, UV, X-rays… Mutagenicity is correlated with carcinogenicity

Lysogenic Conversion Bacteria acquire new traits from viruses (phage) Viruses inject their genes into bacteria Express during lysogenic phase Example: Diphtheria toxin

In lysogenic conversion, the trait acquired is FROM the virus.

Transduction Bacterial genes picked up by viruses Happens as bacteria fall apart during lysis Carried to another bacteria during next infection Any bacterial gene – antibiotic resistance

In transduction, the trait acquired is FROM the previous host BACTERIUM. The virus acts ONLY as the CARRIER.

Transformation Some bacteria suck up DNA from environment Common in soil - decomposition, lots of DNA Implications in a hospital… what do you think? Conjugation Exchange of plasmid by sex pilus Donor sex pilus attaches to recipient Copy of plasmid moves through pilus Antibiotic resistance on plasmids Genetic Engineering or Recombinant DNA Cut/paste human and viral genes on plasmids Express “recombinant” plasmids in microbes Why? Faster, cheaper, safer, more ethical Products – insulin, clotting factors, vaccines…

The process of cut/paste/express is called genetic cloning - NOT to be confused with embryonic cloning.

Gene Therapy Replacing bad genes in people with good ones Works only with well-defined genetic diseases Insert good genes into mild lysogenic viruses Infect people with modified lysogenic viruses So Far – some leukemia, cystic fibrosis treated

Performed on adults using inhaled virus or bone marrow-infecting viruses. Theoretically possible to do on embryos.