Chapters 1 & 10 Flashcards
Microbiology
The study of “small organisms,” which are usually invisible to the naked eye; 20 nanometers: smallest virus - 3-4 um, largest - protozoans
Microbes
General term encompassing microorganisms and viruses; diverse in terms of their appearance, metabolism, physiology, reproduction, and genetics. Ex. bacteria, viruses, protist, fungi, helminthes (larva stages - parasitic worms)
Leeuwenhoek (1632-1723)
- Inventor of the first microscope, which could magnify objects up to 300X
- First to use microscopes to observe microorganisms in pond water (1674), which he called “animacules”
- Created detailed descriptions of his findings (pond water, plants, insects, tooth scrapings, etc.) over the next 50 years
- Considered to be the “father of microbiology”
Robert Hooke
Fist to describe “cellulae” (small rooms) in cork in 1665, which led to the formulation of the cell theory by others
Matthias Schleiden and Theodor Schwann
Independently published statements that “cells are the basic organizational unit of all living things” - The Cell Theory (1800s)
Spontaneous Generation
The discredited belief that organisms could arise from non-living matter (worms on meat/rats from hay)
Biogenesis
All living cells arise from other pre-existing living cells
Science
An organized body of knowledge about the natural world
Scientific Method
A series of steps used to gain information about the natural world:
- Make an observation/identify a problem
- Gather information about observation/problem
- Formulate a hypothesis (educated guess)
- Conduct a controlled experiment: contol group, experimental group, collect data
- Conclusion: does your data support or refute the hypothesis
- Peer review
The Progression of Scientific Ideas
- Ideal hypothesis is generated
- Experimentation: hypothesis confirmed or rejected
- Peer review/Publication
- If published, scientific community conducts further experimentation
- If experimental data is consistent and reliable then, with time, the original hypothesis becomes a theory
- Consistently supported theories, over long periods of time, can be elevated to scientific law or a constant fact of nature
Francisco Redi
In 1668, he covered rotting meat with fine gauze, showing that maggots developed only in meat that flies could reach to lay eggs; spontaneous generation would not be refuted for another 200 years because many insisted that only spontaneous generation of microorganisms was disproved
Needham’s Hypothesis, Experiment, and Conclusion
- He boiled chicken broth, put it in a flask, and sealed it
- If microbes grew, then it could only be because of spontaneous generation
- Microbes grew, but we now know this was because the flask was not sterilized before adding the broth
Spallanzani’s Hypothesis, Experiment, and Conclusion
- He put broth in a flask, boiled it, and sealed it creating a vacuum (no air)
- No microbes in the cooled broth
- Critics said he didn’t disprove spontaneous generation, only that it required air
Louis Pasteur’s Experiments
- Argued against spontaneous generation; allowed the free passage of air, but prevented the entry of microbes
- Boiled meat broth in a flask which sterilized it; swan neck flask created a seal with water and bacteria
- No microbes developed until flask was tilted so some broth flowed into the curved neck
- Gravity had caused microbes to settle at the low point of the neck, never reaching the base until washed in with the broth
- Could not be replicated by other scientists who used vegetable broth which contains many endospores; original experiment used meat broth (luck) which contains few endospores
John Tyndall
Explained the conflicting results of Pasteur’s experiments, and proved him correct; He concluded that some microorganisms exist in two forms:
- a cell form that is easily killed by boiling
- a cell form that is heat resistant: endospores
3 Things Proved by Pasteur’s Experiments
- No living things arise by spontaneous generation
- Microbes are everywhere (even in air and dust)
- The growth of microbes causes dead plant and animal tissue to decompose and food to spoil (led him to develop the technique of pasteurization which kept wine from spoiling)
*Also contributed to the development of vaccines
Germ Theory of Disease (late 1800s)
Microbes cause disease, and specific microbes cause specific diseases; previously thought to be caused by “bad air” or linked to superstitions or religion (punishment)
Ignaz Semmelweis (1850)
- Noted that the rate of childbirth infections were greater at teaching clinics than when staffed by midwives
- Doctors went from mother to mother - microbes from infected patients could spread to other patients
- Midwives only worked with one patient
Joseph Lister
- Believed pus around wounds was caused by microorganisms and that if they were killed the wounds might heal faster
- Dressed wounds in phenol soaked cloths, reducing the rate of infection and speeding up the healing process
- Proposed and practiced the idea of antiseptic surgery (sprayed phenol of the patients)
- Phenol is not only toxic to most microorganisms, but humans as well (powerful carcinogenic); no longer used as an antiseptic
Robert Koch (late 1870s)
- Studied anthrax: disease of cattle/sheep but also in humans
- Observed that microbes were present in all blood samples of infected animals
- Isolated and cultivated these microbes (Bacillus anthracis)
- Injected healthy animal with cultured bacteria and it became infected; blood sample showed same microbes
- Proved that particular microbes cause particular diseases
Koch’s 4 Postulates Concerning Disease and Microorganisms
- The suspect agent must be present in every individual with the disease
- The suspect agent must be isolated and grown in pure culture
- The pure culture must cause the disease when injected into a healthy, experimental animal
- The suspect agent must be re-isolated from the experimental animal and re-identified in pure culture (eliminates coincidence)
Free-Living Organisms
An organism that is not directly dependent on another organism for survival
Autotrophs
Organisms that:
- Use inorganic molecules or photons (light particles) to create cellular energy (ATP)
- Use CO2 as their principle source of carbon atoms to create new organic molecules necessary for maintaining their life
Photoautotrophs
Use light energy to create ATP, and CO2 for their carbon source
Chemoautotrophs
Use inorganic molecules (e.g. hydrogen sulfide gas) to create ATP and CO2 as their carbon source
Heterotrohps
Organisms that:
- Use organic molecules from other organisms to create cellular energy (ATP)
- Use organic molecules in other organisms to create new organic molecules necessary for maintaining their life
Decomposers
Organisms that use simple organic molecules from dead organisms:
- Use organic molecules from dead molecules to create cellular energy (ATP)
- Use organic molecules form other dead organisms to create new organic molecules necessary for maintaining their life
Symbiosis
Occurs when two organisms live together
- symbiont: smaller organism
- host: larger organism
Mutualistic Symbiosis
Both the symbiont and the host benefit from the relationship; acid producing bacteria in the vagina retards growth of yeast while human provides a location, warmth, nutrition, and growth
Commensalistic Symbiosis
The symbiont receives a benefit from the relationship but does not harm the host
Parasitic Symbiosis
The symbiont benefits by the relationship but the host is harmed by it
Exotic Parasites
A pathogen not typically found in the human body, but can invade and cause harm; most flu and cold viruses are not usually found in the human body, they must be introduced by a host
Opportunistic (Endemic) Parasites
Pathogens that are normal residents of the human body, but only inflict harm to the host when its immunity is weakened; streptococcus pneumonia
Taxonomy
The classification and identification of organisms
Classification
The orderly arrangement of organisms into groups that have similar characteristics; all schemes are constantly under review and are subject to change
Kingdom
The broadest classification of organisms; species in the classification level can be very different
Questions Determining an Organisms Kingdom Classification
- How many cells does the organism have? Unicellular or Multicellular
- Does the cell(s) have a nucleus? Prokaryotic or Eukaryotic
- How does the organism get its energy and nutrients? Autotroph or Heterotroph
- Cell wall composition? Cellulose, Peptidoglycan, or Chitin
Kingdom Monera/Prokaryotes
- Prokaryotic
- Unicellular
- Chemoautotrophic or photoautotrophic or heterotrophic (decomposers, parasites, commensalistic, mutualistic)
- Cell wall made from peptidoglycan in true bacteria
- Ex: bacteria, blue-green algae, archeabacteria*
Kingdom Protist
- Eukaryotic
- Unicellular
- Photoautotrophic and/or heterotrophic
- No cell walls
- Ex: Amoebas, Paramecium
Kingdom Fungi
- Eukaryotic
- Most are multicellular, but some are unicellular (yeast)
- heterotrophic by absorption (strictly decomposers), secrete powerful enzymes that break down matter
- Cell walls made from chitin
- Ex: yeast, mold, mushrooms
Plant Kingdom
- Eukaryotic
- Multicellular
- Photoautotrophic: use photosynthesis to produce energy
- Cell walls made from cellulose
- Ex: mosses, ferns, conifers, flowering plants
Animal Kingdom
- Eukaryotic
- Multicellular
- Heterotrophic by consumption and digestion
- No cell walls
- Ex: coral, sponges, insects, reptiles, birds, mammals
Carolus Linnaeus
In 1753, recommended the use of binomial nomenclature for the scientific naming of organisms; would reduce confusion in the scientific community; name would consist of two Latin words (dead language): genus name (always capitalized) and species name (never capitalized) which are either italicized or underlined; usually descriptive, honorary, or both
Strains (Varieties)
Isolated sub-populations of bacteria that are of the same species but have slightly different characteristics
Phylogenetic Tree
A branching diagram showing the inferred evolutionary relationship among organisms based upon similarities and differences in their physical and/or genetic characteristics
Differences Between Domain Bacteria and Domain Archaea
- Bacteria and Archaea are as genetically different as Bacteria and Eukarya
- In Bacteria, the cell wall is made of peptidoglycan; Archaea have cell walls that are not made of peptidoglycan, composition varies greatly
- Archaea can thrive in extreme environments: high salinity (10x ocean water), high or low temperatures (105’ C, 0’ C)
- Archaea species rarely, if ever, cause disease
Infectious Agents
An agent capable of causing an infection:
- Capable of self-replications (some form of reproduction)
- Free-living include bacteria, algae, fungi, protozoa, helminthes (larval stages)
- Non-living include viruses, viroids, and prions
Virus
- Acellular: not considered prokaryotic or eukaryotic
- A piece of DNA or RNA surrounded by a protective protein layer (capsid); no nucleus of organelles or cell membrane or cytoplasm
- 1/10 to 1/1000 the size of an ordinary bacterial cell
- nonmotile
Viroid
- A small piece of RNA that is not surrounded by a protein layer
- Plant pathogens; uncertain for animals
- Potato spindle tuber disease
Prion
- A small self-replicating protein, no RNA or DNA
- Affect the structure of the brain or other neural tissue and all are currently untreatable and universally fatal
- Bovine spongiform encephalopathy (“mad cow disease”)/Creutzfeldt-Jakob Disease (CJD)
Microbe Functions Necessary for Human Life
- Nitrogen Fixation: Bacteria convert nitrogen gas (N2) into a solid form that is usable by plants, then other organisms
- Oxygen gas (O2) production
- Biodegradation: Microorganisms can break down glucose and other organic debris in the process of decomposition, instead of it accumulating within the environment
Economic Applications of Microbiology
- Alcohol production; wine, beer, spirits (yeast)
- Food production: vinegar, yogurt, cheese, bread
- Drug production; Insulin, Interferon, ethanol, antibiotics
- Bioremediation: Help clean up the environment; bacteria can often break down toxic or unwanted waste products (oil spills)
- Agricultural: research has led to healthier livestock and disease-free crops
