Bacteria
Malthus (late 1700's) "Populations expand until they are limited by some form of misery (starvation, disease) or vice (birth control, war, manmade means)"
Darwin (late 1800's) When resources are scarce who lives and who dies? Survival of the fittest = natural selection
Questions:
1. How do organisms inherit their parents characteristics?
2. Where does novelty come from?
BIOCHEMISTRY (analyze reactions; purify molecules) + GENETICS (inheritance; information for cell) + MICROBIOLOGY (use simple organisms) => MOLECULAR BIOLOGY
Life forms
1. Viruses - not truly life or a cell, just a package of genes
Living cells:
2. Prokaryotes - bacteria, simple cells with out a nucleus
3. Eukaryote - higher organisms, complex cells with a nucleus like plants, animals and fungi
Genes contain the cell information:
-they run the cell machinery (RNA)
-pass on a copy to each descendent (DNA)
Genome = complete set of information usually in the form of DNA= all of the genes
Typical bacterial cell has 2,000 - 4,000 genes
Eukaryotes can have 50,000 - 100,000 genes
Bacterial size
Bacteria usually about 1 micron in length by 1/2 micron wide
1 micron = 10-6 meter or 1 mm
Bacterial Species
E. coli or Escherichia coli - most often used in molecular biology
(Escherichia - genus) (coli - species)
PROKARYOTE |
EUKARYOTE |
| simple | complex |
| fast growth | slow growth |
| small cells | large cells |
| single-celled | multicellular |
| one circular chromosome | several linear chromosomes |
| haploid (one copy of each gene) | diploid (two copies of each gene) or more |
| Organelles Without Membranes | |
| ribosomes | ribosomes |
| flagella (simple) | (see below) |
| Membranous Organelles | |
| none | nucleus |
| none | cytoplasmic reticulum and golgi |
| none | mitochondria (contain DNA) |
| none | chloroplasts (in plants, contain DNA) |
| none | flagella (more complex, have membranes) |
Bacteria:
1. Easy to grow
-grow in simple medium with one sugar and minerals
-divide fast (some can divide once every 20 minutes)
2. Single cells
-all identical
-colonies picked for easy genetic analysis
3. Haploid
-one copy of each gene
Virus -
can only replicate inside a cell
can infect bacteria, known as bacteriophage, or higher organisms
have either RNA or DNA, cannot carry both
Bacteria: Simplest free-living cells, typically 3000 genes. Some parasitic mycoplasms have only about 500 genes
Viruses: not cells
-do not generate energy
-do not make proteins by themselves
-are obligate parasites
Colds are usually cause by Rhinovirus, about 100 types are known and they contain about 1/2 dozen genes.
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SIUC / College of Science / Microbiology / courses / MICR302
URL: http://www.micro.siu.edu/micro302/bacteria.html
Last updated: 4-Feb-99 / laa