The first part of this lecture will be horizontal gene
transfer.
All bacteria
require two things for growth:
1) A
source of energy
2) A
source of matter for building additional cells:
C, O, H, N, S, P, trace minerals.
Elemental Assay of
E. coli (dry weight)
50%
carbon
20%
oxygen
14%
nitrogen
8%
hydrogen
3%
phosphorus
2%
sulfur
2%
potassium
0.05%
calcium, magnesium, chlorine
0.2%
iron
0.3%
trace elements
Carbon,
the backbone of functional biological molecules: cells vary in their ability to
synthesize all of their carbon compounds. Range of carbon compounds utilized:
CO, CH4, to complex organic compounds.
Hydrogen: structural
molecule, participant in process of energy generation. Protons (H+)
involved in ATP production, CO2 reduction, anaerobic and aerobic
respiration.
Nitrogen
in amino acids, nucleic acids. membranes, cell walls, and most macromolecules.
Most free-living microbes assimilate ammonia from their environment or reduce
nitrate. An array of microbial types can "fix" atmospheric nitrogen.
Sulfur in
certain amino acids, some B-vitamins (biotin and thiamine). Reduced inorganic
sulfur (e.g. H2S) used as energy source for thiobacilli. Sulfur
serves as terminal electron acceptor in some Archaea.
Phosphorus:
a constituent of high energy compounds (ATP), phospholipids in membranes,
nucleic acids.
Oxygen:
equal amounts in aerobes and anaerobes, but free oxygen toxic to anaerobes, so
they obtain it in a combined form from the substrate.
Trace elements, though not required in large amounts, are essential for cellular
growth:
Some Important Cofactors and Examples of Their
Functions:
K+ Principle
cellular counterion
Mg++ DNA polymerase
Ca++ Intracellular signalling,
wall structure
Fe++ Cytochromes
Mn++ PsII, photosynthesis
Co++ Vitamin B12 constituent
(methylations)
Cu++ Superoxide dimutase
Zn++ Some DNA binding proteins
Organic Growth Factors are essential organic compounds that an organism is
unable to synthesize. They must be obtained directly from the environment.
Examples: Vitamins, Amino acids, Purines, pyrimidines
These
elements are assembled into macromolecules:
The
composition of prokaryotic cells
%
dry Weight
Protein 55
RNA 20.5
Ribosomal 80%
of total RNA
Transfer
15%
of total RNA
Messenger
5%
of total RNA
DNA 3.1
Lipid 9.1
Lipopolysaccharide 3.4
Peptidoglycan 2.5
Glycogen 2.5
Bacteria are often
categorized according to their source of carbon, energy, and electrons
(hydrogen
Carbon
sources:
Autotrophs CO2
sole or principal source
Heterotrophs Reduced organic molecules
Energy
sources:
Phototrophs Light
Chemotrophs Oxidation of organic or inorganic compounds
Hydrogen
sources:
Lithotrophs Reduced inorganic molecules
Organotrophs Organic molecules
Photolithotrophic
autotroph
Photoorganotrophic
heterotroph
Chemolithotrophic
autotroph
Chemoorganotrophic
heterotroph
1.
I am Rhodobacter, a bacterium
living in a polluted lake. I am photosynthetic and use organic matter as both
an electron donor and a source of carbon. I am
a_______________________________.
2.
I am Helicobacter, a pathogenic
microbe. I use organic compounds as sources of energy, electrons, and carbon
for biosynthesis. I am a ______________________.
3.
I am Spirulina, a cyanobacterium. I
am photosynthetic, splitting water as a hydrogen source just like green plants.
I am a ______________________________.
4.
I am Thiobacillus. I live by
oxidizing sulfur; this gives me both energy and electrons for biosynthesis. My
carbon source is carbon dioxide. I am a ___________________________________.