Chapter 1 Lecture 2 Flashcards
Microbial genetics:
Ribozymes- RNA molecules with ability to catalyze reactions
RNA could serve the dual purpose of genetic information storage AND catalyzing reactions!
Lipid membrane formed around RNA
Earliest Molecules—RNA
Original molecule must have fulfilled protein and hereditary function.
Ribozymes.
RNA molecules that form peptide bonds.
Perform cellular work and replication.
Earliest cells may have been RNA surrounded by liposomes.
Today’s Versions of RNA vs. Ancient Versions
Cellular pool of RNA in modern day cells exists in and is associated with the ribosome (rRNA, tRNA, mRNA).
RNA catalytic in protein synthesis.
RNA may be precursor to double stranded DNA.
Adenosine triphosphate (ATP) is the energy currency and is a ribonucleotide.
RNA can regulate gene expression.
Evolution of Cellular Microbes
Mutation of genetic material led to selected traits.
New genes and genotypes evolved—producing mosaic of genetic information.
Bacteria and Archaea increase genetic pool by
horizontal gene transfer within the same generation
Endosymbiotic Hypothesis
When/how did eukaryotes appear?
Endosymbiotic theory:
Primitive prokaryotic microbes ingested other microbes, starting a symbiotic relationship, forming the first basic eukaryotes.
- Ingested microbes that could use oxygen for a respiratory process to produce chemical energy became mitochondria.
- Ingested microbes that could fix carbon dioxide into organic molecules using light energy became chloroplasts.
Endosymbiotic theory: Evidences
- SSU rRNA genes show bacterial lineage.
- Genome sequences closely related to proteobacteria and Prochloron, respectively.
Hydrogenosomes.
- Anaerobic endosymbiont.
Microbial Species
Eukaryotic microbes fit definition of reproducing isolated populations.
Bacteria and Archaea are referred to as strains which are….
- A strain consists of descendants of a single, pure microbial culture.
- May be biovars, morphovars, serovars, and pathovars.
Bacteria and Archaea reproduce _____
Asexually
Binomial nomenclature.
Genus and species epithet.
Assigning Specific Names
Binomial (scientific) nomenclature
Gives each microbe 2 names:
- Genus - capitalized
- species - lowercase
Both italicized or underlined
Staphylococcus aureus (S. aureus)
Inspiration for names is extremely varied and often imaginative!
The Origin and Evolution of Microorganisms
Phylogeny: natural relatedness between groups of organisms
Evolution
All new species originate from preexisting species
Closely related organism have similar features because they evolved from common ancestral forms
Evolution usually progresses toward greater complexity
Phylogeny
natural relatedness between hroups of organisms
Earliest Metabolism
Early energy sources under harsh conditions.
- Inorganics, for example, FeS.
Photosynthesis.
- Cyanobacteria evolved 2.7 billion years ago.
- Stromatolites—mineralized layers of microorganisms.
Stromatolites
mineralized layers of microorganisms
Energy Sources
Chemicals –>
Chemotrophy –>
Organic–> Chemoorganotrophs–> ATP
or
Inorganic–> Chemolithotrophs–> ATP
Light –>
Phototrophy–>
Phototrophs–> ATP
Chemoorganotrophs
Regardless of how they get organic molecules, they are then broken down by microbes to harness chemical energy (A T P).
- Fermentation doesn’t need oxygen but doesn’t yield much energy for microbes.
- Aerobic respiration does require oxygen but yields much more energy!
Microbial Ecology
How do microbes interact with the world around them?
Microbes can also help in biogeochemical cycling as they interact with the environment.
- This is a process by which inorganic molecules are cycled to organic molecules and back again.
Microbes live in diverse groups in nature, with many different members forming a microbial community and ecosystem.
Name some
- Microbes in the intestines
- Plaque on teeth
- Slime on rocks on beaches
- Mold growths on bathroom surfaces
Great Plate anomaly
Microbes will not behave normally in an isolated laboratory environment (replicate, reproduce, feed, etc.), even if food source is present, they work as a community, so when they are isolated from community, they sense something is off.
Microbial Biotechnology
Can studying the genetics of microbes help us to use them to benefit humans? YES!
- By altering the genomes of microbes, we can mass-produce molecules that humans want.
- A classic example of this is the production of human insulin by inserting the gene into E. coli cells (done in 19 78 by Genentech in San Francisco).
Major Fields in Microbiology
Medical microbiology—diseases of humans and animals.
Public health microbiology—control and spread of communicable diseases.
Immunology—how the immune system protects a host from pathogens.
Microbial ecology is concerned with the relationship of organisms with their environment.
Agricultural microbiology is concerned with the impact of microorganisms on food production.
Food microbiology—microbes used to make food and beverages as well as spoilage microbes.
More Microbiology Fields
-Industrial microbiology.
Penicillin and other antibiotics.
Vaccines, steroids, alcohols and other solvents, vitamins, amino acids, enzymes, and biofuels.
-Microbial physiology studies metabolic pathways of microorganisms.
-Microbial genetics, molecular biology, and bioinformatics study the nature of genetic information and how it regulates the development and function of cells and organisms.
–Synthetic Microbiology
Microbes are a model system of genomics.
Microbes and Disease
How are microbes associated with disease?
-We didn’t always believe that microbes caused disease or existed around us unseen.
-People used to believe that disease was associated with angry gods or bad air.
-Even when microbes were known to exist, people thought they could spontaneously form as life from nonliving matter (the spontaneous generation theory).
-It took the work of many people to debunk these ideas, but two were very important: Louis Pasteur and Robert Koch.
Louis Pasteur
Louis Pasteur performed a simple yet elegant experiment to disprove spontaneous generation theory in the late 1800s.
Robert Koch
Robert Koch determined Bacillus anthracis and Mycobacterium tuberculosis were the causes of anthrax and tuberculosis (respectively).
His work with anthrax helped sheepherders and cattle ranchers avoid costly animal losses.
Koch’s Postulates
1) the microorganism must be present in every case of the disease but absent from healthy individuals
2) the suspected microorganism must be isolated and grown in a pure culture
3) the same disease must result when the isolated microorganism is inoculated into a healthy host
4) the same microorganism must be isolated again from the diseased host
The basic rules Koch established made it possible for others to determine which microbes caused which diseases. They are still in use to this day
Limitations of Koch’s Postulates
some organisms cannot be grown in pure culture (e.g. Mycobacterium leprae)
using humans in completing the postulates is unethical (e.g. Ebola hemorrhagic fever)
molecular and genetic evidence may be used instead
20th century disease
In the twentieth century, we have seen a dramatic drop in U.S. deaths from infectious diseases
Microbes & Infectious Diseases
Pathogens: Microbes that do harm
Nearly 2,000 different microbes cause diseases
10 B new infections/year worldwide
12 M deaths from infections/year worldwide
Where has this reduction in deaths come from?
Prevention of infection through
-Use of antiseptics (Joseph Lister)
-Sanitation improvements (sewage treatment)
-Food/water safety (pasteurization)
-Personal hygiene improvements
-Vaccination
Treatment of infections (antibiotics!)
