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Chapter 1

BLG 151 Chapter Notes - Chapter 1: Recombinant Dna, Acronym, Hyperlink

Course Code
BLG 151
Kimberley Gilbride

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-microorganisms: organisms & acellular biological entities too small to be seen clearly by
unaided eye, 1mm in dimeter
- can be
1. colonial- consisting of small aggregations of cells, seen without microscope
2. Multicellular: lack highly differentiated tissues
3. Most unicellular are microscopic. – Hard to classify microbes who have similarity with plants
and animals could be classified as prokaryotic: contents not divided by membrane or eukaryotic:
have membrane bound organelles
- Comparison of rRNA by Cal Woose demonstrated that bacteria and archaea are very different,
currently 3 domains: Archaea, bacteria and Eukarya
- Bacteria : single-celled, has cell wall(peptidoglycan), some members of phylum
Planctomycetes have membrane, abundant in soil, water, humans, air, extreme temperatures, pH,
salinity , most play a beneficiary role
- Archaea- distinctive rRNA, no cell wall, unique membrane lipids, unusual metabolite capacity
(methanogens), live in extreme environments: halophiles, thermophiles
- Eukarya: include protest, fungi, plant and animal. Protest: typically larger than bacteria and
1. Algae are photosynthetic
2. Slime molds- act as protozoa in one part of life and fungi in another
3. protozoa- unicellular, animal-like, motile, hunters, obtain food by ingesting organic matter or
microbes, some disease causing
4. Water molds- grow on surface of freshwater & moist soil, feed on decaying vegetation (logs),
and produced many plant infections
- Fungi ranges from yeast to mushrooms, multicellular fungi , forms hyphae, absorbs nutrients
from environment, plays a beneficial role due to their metabolic capacities, mycorrhizal fungi
( symbiont to plants) helps plant growth by providing additional nutrients , can cause diseases
- Viruses: acellular entities hat must invade a host cell to multiply. Simplest form contains
nucleic acid and proteins.
- Viroid & satellites: infectious agents containing only RNA. Viroid cause plant diseases.
Satellites cause plant & important animal diseases
- Prions: infectious agents composed of only proteins
1.2 Microbial Evolution
- earth 4.5-4.6 billion years old. Living organsims reproduce, obtain energy and use energy.

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-extant organisms: organisms present today
- before life: water (gas), co2, n present n atmosphere, oceans: methane, hydrogen gas, COOH,
shallow pools & hydrothermal vents provided site of chemical rxn , some products acted as
catalysts or played a role in metabolism
- 3 molecules of life:
1. Proteins do cellular work (enzymes)- involves RNA & proteins for synthesis
2. DNA just stores information & requires proteins
3. RNA synthesized from DNA. RNA world hypothesis: RNA could store, copy & express
genetic information in early life. Lipids also formed RNA. Ribozymes: catalytic DNA
- rRNA catalyzed peptide bond, ATP, is also a RNA, RNA can regulate gene expression. DNA is
chemically more stable, hence used today.
- Evolution of metabolism: by archaea ( could be FeS)& photosynthesis( by cyanobacteria,
stromatolites: layered rocks formed by incorpation of mineral sediments into layers of
microorganism growing as thick mats on surface
- Phylogenetic tree- graph made of nodes & branches that shows phylogenetic relationships
between groups of organism & shows evolutionary relationships. SSUrRNA gene sequences
compared, # of difference was counted. More differences indicated that more evolutionary
distance between them. It is a molecular tree, not an organismal tree and difference between
branch tips is a measure of relatedness. LUCA common ancestor in bacteria domain.
- Endosymbiotic hypothesis: origins of chloroplast, mitochondria & hydrogenosomes;
Endosymbiosis: interaction between two organisms in which 1 lives inside another. Mitochondria
& chloroplasts contain DNA & ribosomes; like a bacterial cell. Hydrogen hypothesis:
endosymbiont was anaerobic bacterium that produced h2 (G) & CO2, became dependent on
hydrogen gas & evolved into mitochondria, chloroplast or hydrogenosome: organelle that
produces ATP by fermentation.
- Natural selection & isolation of populations lead to development of new collection of genes &
many species
- Genetic diversity in eukaryotes: reproduce sexually, in prokaryotes: horizontal gene transfer
(HGT): genetic info from a donor organism is transferred to a recipient.
- Species (animal & plants): interbreeding or potentially natural interbreeding population that is
reproductively isolated from other groups. Species (prokaryotes): collections of strains that share
many stable properties & differ significantly from other groups of strains. Strain: descendant of a
pure, single microbial culture
1.3 Microbiology & it’s Orgins
- microbiology: organisms studied + tools used to study them

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- Lewwenhoek made 1st microscope. Robert hooke made 1st drawings of microorganisms
- pure/axenic culture: removing microorganisms from their normal habitats and culturing them
isolated from others. Population of cells that are identical because they arise from a single cell.
- Spontaneous generation: living organism could develop from nonliving matter. Pasteur
disproved the spontaneous generation theory. Pasteurization: heating up substance to destroy
undesirable microbes
- Koch’s postulates: set of rules for providing that a microorganism causes a particular disease
- Agar was used as a solidifying agent: not attacked by bacteria, eliminated need to handle
boiling liquid. Development of Petri Dish.
- Attenuated: incubating cultures for long periods of time between transfers, resulted in cultures
that had lost their ability to cause the disease. Vaccine: organism remained healthy & able to
resist the disease with exposed to virulent cultures. Antitoxins are antibodies that specifically
bind toxins, neutralizing them. Phagocytosis: cells engulfing bacteria/ other things.
1.4 Microbiology Today
- microbiology deals with food spoilage, food production, waste water treatement……
- molecular & genomic methods for studying microbes rely on the abilty of scientists to
manipulate genes & genomes of organisms. Genome: all genetic information that the organisms
has. Restriction enzymes/endonucleases: cutting DNA into smaller pieces. Recombinant DNA:
cutting DNA from different organisms with same restriction enzyme, mixing 2 together &
linking them together with DNA ligase.
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