Chapter 1

Microorganisms

An organism that is usually too small to be seen clearly with the naked eye and is often unicellular, or if multicellular, does not exhibit a high degree of differentiation.

Can multicellular organisms be considered as microorganisms?

yes, if it does not exhibit a high degree of differentiation

Types of cellular microorganisms

• fungi

• protists

• bacteria

• archaea

Types of Acelluar microorganisms

• viruses

• viroids

• satellites

• prions

Yeast molds are an example of _____ which are _____ microorganisms

• fungi

  • cellular

Algae, protozoa, and slime molds are examples of ____ which are _____ microorganisms.

• protists

  • cellular

Escherichia coli is an example of _____ which are _____ microorganisms.

• bacteria

  • cellular

Methanogens are an example of _____ which are ____ microorganisms

• archaea

  • cellular

What are viruses composed of?

protein coat and nucleic acid genome

What are viroids composed of?

RNA

Which acellular microorganisms are composed of nucleic acid enclosed in a protein shell?

satellites

What are prions composed of?

protein

Where do the majority of bacteria and archaea live?

in oceans and sediments

• sediments either in earth’s crust or deep below the crust

In which domain do most members have a cell wall containing peptidoglycan?

Bacteria

Members of domain Bacteria are usually ____-celled organisms.

single-celled

Which domain contains protists, fungi, plants, and animals?

Eukarya

Which microorganisms are eukaryotic, generally unicellular, and sometimes colonial?

Protists

Describe the size of protists compared to bacteria and archaea:

protists are larger than most bacteria and archaea

Which infectious agent is a single-stranded RNA not associated with any protein, even for coding and translating proteins?

Viroid

What kind of diseases do Viroids cause?

plant diseases

Which infectious agents are known for causing neurological diseases such as scrapie and mad cow disease?

Prions

Which infectious agents are composed of a nucleic acid enclosed in a protein shell, and must coinfect a host cell with a helper virus?

Satellites

Satellites and their helper viruses cause what kind of diseases?

both plant and animal

Ribozymes

catalytic RNA molecules

What is the unique bacterial cell wall molecule?

Peptidoglycan

Hydrogen hypothesis

says that eukaryotes originated through the development of the hydrogenosome,

an organelle that arose from an endosymbiotic anaerobic bacterium that produced CO2 and H2 via fermentation,

and over time the host became dependent on the H2 produced by the endosymbiont

How do bacteria and archaea increase their genetic diversity, since they do NOT reproduce sexually?

by mutation and horizontal gene transfer (HGT)

Horizontal gene transfer

genetic information from a donor organism is transferred to a recipient, creating a new genotype in the recipient

• info passed btwn same gen individuals and even btwn species in different domains of life

How are Archaea membrane lipids unique compared to Bacteria and Eukarya membrane lipids?

Archaea membrane lipids are glycerol diethers and diglycerol tetraethers

• bacteria and eukarya have ester-linked phospholipids and sterols

Which of the 3 domains have plasmids?

bacteria and archaea

• rare in eukarya

Describe the chromosomes of Bacteria

• usually one circular chromosome

• single origin of replication

• some polyploid

Describe the chromosomes of Archaea

• one circular chromosome

• some have chromosomes w multiple origins of replication

• some polyploid

Describe the chromosomes of Eukarya

• multiple, linear chromosomes

• multiple origins of replication

• usually diploid

Oligonucleotide signature sequence

short conserved regions of a gene that are specific to phylogenetically defined groups of organisms

Unrooted phylogenetic tree

represents phylogenetic relationships but does not indicate which organisms are more primitive relative to others

Rootes phylogenetic tree

includes a node that serves as the common ancestor and shows the development of the four species from this root

Strain

a population of organisms that descends from a single organism or pure culture isolate

Biovars

variant strains characterized by biochemical or physiological differences M

Morphovars

strains that differ morphologically

Serovars

strains w distinctive properties that can be detected by antibodies

Pathovars

pathogenic strains distinguished by the plants in which they cause disease

Microbial dark matter

life known to exist only from nucleotide sampling of environmental samples, never cultivated in lab, properties inferred from genome sequence

Describe two reasons RNA is thought to be the first self-replicating biomolecule:

1. RNA can have catalytic properties (ribozymes) - catalyze protein formation (ex. rRNA catalyzes peptide bond formation during protein synthesis)

2. RNA is ancient, known bc of the ribosome’s use of rRNA, mRNA, and tRNA to construct proteins.

What evidence supports the endosymbiotic theory?

• mitochondria and chloroplasts contain DNA and ribosomes similar to bacterial DNA and ribosomes

• peptidoglycan has been found between the two membranes that enclose the chloroplasts of some algae

Axenic culture

pure; population of cells that are identical because they arise from a single cell

Contributions of Frencesco Stelluti and their importance?

earliest microscopic observation of organisms, on bees and weevils

Contributions of Robert Hooke and their importance?

Micrographia

• first drawings of microorganisms in scientific literature

• info on building microscopes

Contributions of Leeuwenhoek and their importance?

constructed microscopes w double convex glass lenses, magnify 50 to 300 times, dark-field illumination

• saw bacteria and protists ‘animalcules’

Contributions of Francesco Redi and their importance?

discredited spontaneous generation (for larger organisms) via experiments on decaying meat and maggots (maggots come from presence of fly eggs, not spontaneously)

Contributions of John Needham and their importance?

experiment: mutton broth in flasks → boiled → sealed

• results: broth became cloudy and contained microorganisms

supported spontaneous generation for microorganisms (vital force), after Redi maggot experiment

Contributions of Lazzaro Spallanzani and their importance?

experiment: broth in flasks  sealed  boiled

• results: no growth of microorganisms

discredited spontaneous generation after Needham, though there were still deniers

Contributions of Louis Pasteur and their importance?

• swan neck experiment

  • settled spontaneous generation - no growth even tho swan neck flasks were open to air, only growth if swan necks broke

• Pasteurization

• demonstrated that microorganisms carried out fermentations

Contributions of Joseph Lister and their importance?

• developed system of antiseptic surgery to prevent microorganisms from entering wounds

• provided strong indirect evidence for

Germ theory of Disease

idea that microorganisms cause disease

Contributions of Robert Koch and their importance?

directly demonstrated that bacteria cause disease (final proof)

• relationship btwn Bacillus anthracis and anthrax

• Koch’s postulates

  • set of rules for proving that a microorganism causes a particular disease

• led to golden age of bacteriology

Koch’s postulates

criteria for proving the causal relationship btwn a microorganism and a specific disease

Limitations of Koch’s postulates

• microbes that must live in host cells (like viruses) cannot be isolated in pure culture

• lack of appropriate animal model for some diseases, so postulates cannot be fully met

How were viruses discovered?

discovery of viruses made possible from Chamberland’s porcelain filter

• Beijerinck used filter to remove bacteria to study tobacco mosaic disease, but extracts from diseased plants were still infectious = agent smaller than bacterium = virus

Who discovered attentuation? What does this mean?

Pasteur and Pierre Roux

• attenuated bacteria = weakened, injected into chickens and fo

Who used vaccination to protect against smallpox?

Edward Jenner

Who recognized the role of antibodies in preventing disease with diphtheria and rabbits?

von Behring and Kitasato

Who first discovered immune system cells, specifically phagocytes?

Metchnikoff

How did Beijerinck and Winogradsky contribute to microbial ecology?

• found nitrogen-fixing bacteria and sulfate-reducing bacteria

• developed enrichment culture techniques and selective media

What role did the ability to grow bacteria in pure culture play in the development of Koch’s postulates?

the ability to grow bacteria in pure culture demonstrated that the bacteria was indeed the disease causing agent, not another microbe

• test causation in a controlled way