Download Microbial Metabolism and Genetics Energy Production

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
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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.