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Chapter 27 Flashcards

1
Q

History of Microbiology

A

The size of prokaryotic cells led to their being undiscovered for most of human history​

In 1546, Italian physician Girolamo Fracastoro suggested that disease was caused by unseen organisms​

Antony van Leeuwenhoek was first to observe and accurately describe microbial life​

Modern electron microscopes allows the study of cell substructure.​

Louis Pasteur refutes idea of spontaneous generation (idea that living things arise spontaneously from other living things)

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2
Q

Two lines of technology

A

Microscopy for visualization.​

Infectious disease investigations.

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3
Q

Robert Koch studied anthrax; proposed four postulates

A

The microorganism must be present in every case of the disease and absent from healthy individuals.​

The putative causative agent must be isolated and grown in pure culture.​

The same disease must result when the cultured microorganism is used to infect a healthy host.​

The same microorganism must be isolated again from the diseased host.

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4
Q

Prokaryotic Diversity

A

Oldest, structurally simplest, and most abundant forms of life​

Abundant for over a billion years before eukaryotes appeared​

90-99% unknown and undescribed​

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5
Q

Prokaryote Domains

A

Bacteria.​

Archaea.​

Many archaea are extremophiles.

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6
Q

Unicellularity

A

Most are single-celled.​

May stick together to form associations and biofilms.

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7
Q

Cell size

A

Size varies tremendously.​

Most are less than 1 μm in diameter.

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8
Q

Nucleoid

A

Chromosome is single circular double-stranded D N A.​

Found in the nucleoid region of cell.​

Often have plasmids.

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9
Q

Cell division and genetic recombination

A

Most divide by binary fission.​

Exchange genes through horizontal gene transfer; not a form of reproduction.

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10
Q

Internal compartmentalization

A

No membrane-bounded organelles.​

No internal compartment.​

Plasma membrane can be extensively infolded.

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11
Q

Flagella

A

Simple in structure.​

Different from eukaryotic flagella.

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12
Q

Pili

A

Protein filaments extending from the surface

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13
Q

Metabolic diversity

A

Oxygenic and anoxygenic photosynthesis.​

Chemolithotrophic.

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14
Q

Bacteria and archaea differ

A

They differ in four key areas:​

-Plasma membranes​

-Cell walls​

-D N A replication​

-Gene expression

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15
Q

Plasma membrane

A

All prokaryotes have a plasma membrane.​

Membranes of archaea differ from bacteria and eukaryotes.​

Archaean membranes are formed of glycerol linked to hydrocarbon chains by ether linkages (not ester like bacteria & eukaryotes).​

Hydrocarbons may be branched.​

Tetraethers form a monolayer instead of a bilayer; allows extremophiles to withstand high temperatures.

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16
Q

Cell wall

A

All prokaryotes have cell walls.​

Bacteria have peptidoglycan.​

Archaea lack peptidoglycan.

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17
Q

D N A replication​

A

Both have single replication origin; nature of origin and proteins used are different.​

Archaeal D N A replication is more similar to that of eukaryotes.

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18
Q

Gene Expression

A

Archaeal transcription and translation are more similar to those of eukaryotes.

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19
Q

Early systems relied on staining characteristics and observable phenotypes

A

Photosynthetic ability​

Cell wall structure​

Motility​

Unicellular, colony-forming, or filamentous​

Spore-forming ability​

Importance as human pathogens or not

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20
Q

Molecular Classification

A

Amino acid sequences of key proteins​

Percent guanine–cytosine content​

Nucleic acid hybridization​

Closely related species will have more base pairing.​

Gene and R N A sequencing​

Especially rR N A.​

Whole-genome sequencing

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21
Q

Molecular Classification

A

Based on these molecular data, several prokaryotic groupings have been proposed​

Bergey’s Manual of Systematic Bacteriology, 2nd edition​

Large scale sequencing of random samples indicates vast majority of bacteria have never been cultured or studied in detail

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22
Q

Prokaryotic Cell Structure

A

3 basic shapes​

-Bacillus – rod-shaped​

-Coccus – spherical​

-Spirillum – helical-shaped

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23
Q

Prokaryotic Cell Characteristics

A

Cell wall​

Peptidoglycan forms a rigid network.​

Maintains shape.​

Withstands hypotonic environments.​

Archaea have a similar molecule (pseudomurein).​

Gram stain.​

Gram-positive bacteria have a thicker peptidoglycan wall and stain a purple color.​

Gram-negative bacteria contain less peptidoglycan and do not retain the purple-colored dye – retain counterstain and look pink.

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24
Q

Prokaryotic cell walls

A

Gram positive bacteria​

Thick, complex network of peptidoglycan.​

Also contains lipoteichoic and teichoic acid.​

Gram negative bacteria​

Thin layer of peptidoglycan.​

Second outer membrane with lipopolysaccharide.​

Resistant to many antibiotics.

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25
Prokaryotic cell walls 2
S-layer​ Rigid paracrystalline layer found in some bacteria and archaea.​ Outside of peptidoglycan or outer membrane layers in gram-negative and gram-positive bacteria.​ Diverse functions – often involves adhesion.​ Capsule​ Gelatinous layer found in some bacteria.​ Aids in attachment.​ Protects from the immune system.
26
Flagella
Slender, rigid, helical structures.​ Composed of the protein flagellin.​ Involved in locomotion – spin like propeller.
27
Pili
Short, hairlike structures.​ Found in gram-negative bacteria.​ Aid in attachment and conjugation.
28
Endospores
Develop a thick wall around their genome and some of the cytoplasm when exposed to environmental stress​ Highly resistant to environmental stress​ Especially heat.​ When conditions improve can germinate and return to normal cell division​ Bacteria causing tetanus, botulism, and anthrax
29
Prokaryotic cells often have complex internal membranes
Invaginated regions of plasma membrane​ Function in respiration or photosynthesis
30
Nucleoid region
Contains the single, circular chromosome.​ May also contain plasmids.
31
Ribosomes
Smaller than those of eukaryotes.​ Differ in protein and R N A content.​ Targeted by some antibiotics.
32
Prokaryotic cell organization
Internal compartments​ Small number of membrane-bounded structures seen​ Magnetosome in magnetotactic bacteria​ Protein shells called bacterial microcompartments (B M C)​ They isolate specific metabolic processes. ​ Increase concentration of reactants.​ Protect the cell from toxic metabolic intermediates.
33
Prokaryotic Genetics
3 types of horizontal gene transfer​ -Conjugation – cell-to-cell contact.​ -Transduction – by viruses.​ -Transformation – from the environment.
34
Natural transformation
Occurs in many bacterial species.​ D N A from a dead cell picked up by a live cell.​ Proteins for it are on the bacterial chromosome.​ Evolved, not an accident of plasmid or phage biology.
35
Artificial transformation
Some species do not naturally undergo transformation.​ Accomplished in the lab.​ Used to transform E. coli for molecular cloning.
36
Generalized transduction
Virtually any gene can be transferred.​ Occurs via accidents in the lytic cycle.​ Viruses package bacterial D N A and transfer it in a subsequent infection.
37
Specialized transduction
Occurs via accidents in the lysogenic cycle.​ Imprecise excision of prophage D N A.​ These phage carry both phage genes and chromosomal genes.
38
Conjugation
Plasmids may encode functions not necessary to the organism, but may provide a selective advantage​ In E. coli, conjugation is based on the presence of the F plasmid (fertility factor) F+ contain plasmid, F- cells do not (recipient)
39
F plasmid transfer
F+ produces F pilus that connects it to F- cell. Occurs through conjugation bridge. F plasmid copied through rolling replication. Results in two F+ cells.
40
The F plasmid can integrate into the bacterial chromosome
Events similar to crossing over in eukaryotes.​ Homologous recombination.​
41
Hfr cell (high frequency of recombination)
F plasmid integrated into chromosome.​ Replicated every time host divides.
42
The F plasmid can also excise itself by reversing the integration process
An inaccurate excision may occur picking up some chromosomal D N A – F′ plasmid.
43
During conjugation in Hfr strains, the transfer of genes is linear and progressive
Genes farther from the origin of transfer will be transferred later.​ Different marker genes appear in the recipient cell at specific times.​ Gene order can be mapped based on entry time
44
R (resistance) plasmids
Encode antibiotic resistance genes.​ Acquire genes through transposable elements.
45
Genes from pathogenic species transferred by plasmids or transduction
Encode genes for pathogenic traits.​ Enterobacteriaceae.​ E. coli O157:H7 strain evolved by acquiring genes for pathogenic traits.
46
Mutations in bacteria
Mutations can arise spontaneously in bacteria as with any organism
47
Screens of prokaryotic genomes revealed repeated sequences with spacer regions called CRISPR
Clustered Regularly Interspaced Short Palindromic Repeats Adaptive immunity to viral infection Useful for gene editing in the lab
48
Nutritional strategy
how prokaryotes get carbon, get electrons for redox chemistry, and perform energy transformation.
49
Prokaryotes can be classified into five nutritional types 
Chemoorganoheterotrophs​ Chemolithoheterotrophs​ Chemolithoautotrophs​ Photolithoautotrophs​ Photoorganoheterotrophs
50
Prokaryotic Metabolism
Organisms require carbon for building, a source of electrons to use in redox chemistry, and energy for anabolic processes. ​ Nutritional strategy = how they get carbon, get electrons for redox chemistry, and perform energy transformation. ​ How they get carbon:​ Heterotrophs get carbon in reduced forms.​ Autotrophs get carbon in oxidized forms (CO2). ​ How they get electrons for redox chemistry:​ Lithotrophs get electrons from reduced inorganic substances. ​ Organotrophs get electrons from reduced carbon sources. ​ How they perform energy transformation:​ Chemotrophs oxidize reduced chemicals from the environment.​ Phototrophs transform energy by harvesting light.
51
Respirations and fermentations
Prokaryotes have greater diversity to perform respirations and fermentations Eukaryotes - restricted to organic electron donors and oxygen as a terminal electron acceptor (aerobic). Prokaryotic fermentations can metabolize pyruvate and other compounds to recycle electron donors​ Fermentation by-products are industrially and commercially valuable
52
Beneficial Prokaryotes
Decomposers release a dead organism’s atoms to the environment Nitrogen fixers reduce N2 to NH3 (ammonia).
53
Fixation
Photosynthesizers fix carbon into sugars
54
Plants as microbial ecosystems
Mutually beneficial association between plants and bacteria​ Nitrogen-fixing bacteria on plant roots.
55
Parasitic relationships
Parasitic relationships Can harm important crops.​ Example: Crown gall disease
56
Animals as microbial ecosystems
Mutually beneficial association between animals and bacteria​ Cellulase-producing bacteria in ruminants.​ Human microbiome protects against pathogens and aids in digestion.
57
Bacteria in bioremediation
Bacteria are used for bioremediation​ Remove pollutants from water, air, and soil.
58
Biostimulation
adds nutrients to encourage growth of naturally occurring microbes
59
Halorespiration
bacteria remove halogenated compounds from toxic waste
60
Human Bacterial Disease
In the early 20th century, infectious diseases killed 20% of children before the age of five​ Sanitation and antibiotics considerably improved the situation.​ In recent years, however, many bacterial diseases have appeared and reappeared
61
How bacteria cause disease
To cause disease, pathogenic bacteria​ Gain entry to the body.​ Colonize at the site of infection.​ Evade the immune system.​ Spread to other sites in the body.​ Cause damage by the production of toxins or by triggering inflammatory responses.
62
Helicobacter pylori
Can cause stomach ulcers​ Treated by reducing stomach acid.​ Can cause gastritis​ Treated with antibiotics.​ This pathogen can also cause stomach cancer and a type of lymphoma
63
Gonorrhea
One of the most prevalent communicable diseases in North America.
64
Chlamydia
Can cause pelvic inflammatory disease and heart disease
65
Syphilis
Four distinct stages.​ -Chancre – highly infectious​ -Rash – infectious​ -Latency – no longer infectious but attacking internal organs​ -Damage now evident – heart disease, mental deficiency, nerve damage

Biology (18 decks)

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