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Bacteriology & Mycology Flashcards

1
Q

Spontaneous generation

A

Aristotles and others believed that living organisms could develop from non-living materials (because flies flew out of meat)

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2
Q

Biogenesis

A

All living things come from other living things

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3
Q

Scale of bacterial life

A

One cell in body= 10 bacterial cells
Wrap earth 2.5 times laid end to end
Large in number, small in size and invisible to the naked eye

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4
Q

Eukaryotic cells

A

Plant and snimal cells with a nucleus and membrane-enclosed organelles

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5
Q

Prokaryotic cells

A

Unicellular organisms without a nucleus or membrane-enclosed organelles

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6
Q

Bacterial cell structure

A 
Cytoplasm
Ribosomes
Nucleoid
Plasma membrane
Complex and rigid cell wall
Capsule
Flagella
Pili/fimbriae
Endospores
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7
Q

Cytoplasm

A

Cytosol= jelly-like aqueous solution
Contains three main groups of molecules
-macromolecules such as proteins (enzymes), mRNA, tRNA
-small molecules that are energy sources, precursors of macromolecules, metabolites or vitamins
-inorganic ions required for enzymatic activity (co-factors)

Contains the nucleoid (DNA) and ribosomes (protein synthesis)

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8
Q

Cytoplasm function

A 
Facilitate chemical reactions
Dissolve solutes (carbohydrates and proteins)
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9
Q

Nucleoid

A

Location in prokaryotic cell where primary genetic material is found
Bacterial genome
Proteins
-proteins involved in DNA compaction
-transcription factors that regulate the expression of the bacterial genome
RNA
-mRNA coding for proteins
-ncRNA involved in DNA organization and expression of the bacterial genome

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10
Q

Bacterial genome

A

Single haploid circular chromosome containing double-stranded DNA

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11
Q

Plasmid

A

Circular molecule of DNA that replicates separately from the genome
Not part of the nucleoid
Plasmid genes are not essential under normal conditions
Several different plasmids may be present in individual bacterial cells

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12
Q

Plasmid function

A

Contain genes associated with disease (virulence factors) or to survive in presence of antibiotics and other toxic compounds (resistance genes)
Conjugative plasmids: cell-to-cell transfer by conjugation

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13
Q

Conjugative plasmids

A
  1. Donor cell attaches to a recipient cell with its pilus. The pilus draws the cells together
  2. The cells contact one another
  3. On strand of plasmid DNA transfers to the recipient
  4. The recipient synthesizes a complementary strand to become an F+ cell; the donor synthesizes a complementary strand, restoring its complete plasmid
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14
Q

Ribosomes

A

Ribonucleoproteins with large 50S subunit + small 30S subunit
All protein synthesis takes place on ribosomes
Bacterial ribosomes are structurally different from those in eukaryotic cells
Applications
-ribosomes as a target for antibiotics
-16S rRNA gene encoding for component of 30S subunit is used in reconstructing phylogenies

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15
Q

Bacterial envelope

A 
Cytoplasmic or plasma membrane
Cell wall (peptidoglycan layer)
Periplasmic space
Outer membrane (Gram - bacteria)
Capsule (some bacteria)
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16
Q

Plasma membrane

A

Innermost membrane, next to cytoplasm

Composed of a phospholipid bilayer and proteins

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17
Q

Phospholipid bilayer

A

Layer of phospholipid molecules with a head that loves water (hydrophilic) and two tails that fear water (hydrophobic). Only hydrophobic (lipid soluble) compounds can enter the cell by passive diffusion through the lipids in the bilayer

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18
Q

Membrane Proteins

A

Transport proteins enable specific transport of molecules into and out of the cell
Energy generation components used for the synthesis of adenosine 5’-triphosphate (ATP)
Proteins that function as anchors or help in the assembly of external structures

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19
Q

Plasma membrane functions

A

Selective permeability barrier: transport proteins mediate passage of hydrophilic substances into and out of the cell
Bacterial respiration and energy generation
Serve as an anchor for external structures

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20
Q

Cell wall: peptidoglycan layer

A

Peptidoglycan: polymer unique to prokaryotic cells
Mech-like structure consisting of chains of alternating subunits of NAG and NAM cross-linked with peptides by transpeptidase enzymes called penicillin-binding proteins (PBPs)

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21
Q

Peptidoglycan layer function

A

Protection against mechanical damage and osmotic lysis
Transport: non-selective permeability
Composition of bacterial envelope determines the two main structural classes

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22
Q

Outer membrane

A

Common to gram negative bacteria
Protein-containing asymmetrical lipid bilayer
-lipopolysaccharide (LPS or endotoxin)
-porin proteins that allow small hydrophilic molecules to passively enter the cell
Transporter proteins that enable transport of larger nutrients into the cell

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23
Q

Outer membrane function

A

Selective permeability barrier
Resistance to larger or hydrophobic toxic compounds
Tolerance to detergents and bile salts

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24
Q

Lipopolysaccharides

A

Virulence factor

Lipid A component is molecule with endotoxic activity

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25
What will you see from LPS
``` Fever Leukopenia Anorexia Diarrhea Blood coagulation Hemorrhagic shock ```
26
Myobacteria
Bacterial envelope- gram positive bacteria but contains mycolic acid Acid fast staining for identification
27
Mollicutes (mycoplamsa)
Plasma membrane with sterols | No cell wall- no peptidoglycan layer
28
Capsule
Glycocalyx= polysaccharide layer | Only in some bacterial species
29
Capsule function
Protection from adverse environmental conditions (desiccation) Virulence factor facilitate adherence to surfaces and interfere with phagocytosis Nutrient reserve
30
Endospore
cryptobiotic state of dormancy and most durable type of cell found in nature Produced by pathogenic genera Bacillus and clostridium
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Endospore function
ensure survival during adverse environmental conditions | Dormant highly resistant bodies
32
Flagella
Present on bacterial surface Flagellar arrangement -number of flagella -position at which flagella are inserted into bacterial cell wall
33
Flagella function
Locomotion or bacterial motility
34
Pili/Fimbriae
fine, straight, hair-like appendages attached to cell wall | most common on gram-negative bacteria
35
Pili/Fimbriae function
Adhesion to host tissues | Contribute to antigenicity
36
Bacterial shapes and arrangements
Cocci Bacilli Budding and appendaged bacteria
37
Bacterial colony appearance
A single bacterium multiplies on solid growth media. Growth of bacteria produces a bacterial colony that is visible without a microscope Some bacteria need to be cultured in broths in which tubidity indicates growth Same bacterial species can have different morphology depending on the culture medium, incubation time/temperature/oxygen or genetic difference
38
Factors required for bacterial growth
Sources of metabolic energy: fermentation, respiration and photosynthesis Environmental factors -nutrients -pH (most pathogenic bacteria grow best at 7.2-7.4) -ionic strength and osmotic pressure -light -Temperature (most are mesophilic with growth at 30-37 C) Gaseous requirement: oxygen and carbon dioxide
39
Classification of bacteria
``` Based on oxygen requirement -Obligate aerobes -obligate anaerobes -Facultative anaerobes -Aerotolerant anaerobes Based on temperature range for optimal growth ```
40
Bacterial growth curve
``` Bacteria replicate by binary fission Generation time Four phases -Lag phase -Exponential phase or logarithmic phase Maximal stationary phase -Decline phase or death phase ```
41
Generation time
length of time required for a single bacterial cell to yield two daughter cells (30 min to 20 hours)
42
Lag phase
Increase in cell size, active metabolism of cells but no division
43
Exponential phase or Logarithmic phase
cells multiply at maximum rate
44
Maximal stationary phase
Due to exhaustion of nutrients or accumulation of toxic products, growth is ceased, balance between slow multiplication and death rate
45
Decline phase or death phase
progressive death of cells
46
Fungal Characteristics
Eukaryotic Non-photosynthetic heterotrophs: produce exoenzymes to obtain nutrients by absorption Widely distributed in the environment Fungi grow aerobically and many are strict aerobes Cell membrane contains sterols and plant-like cel wall with chitin, glucan and mannoproteins
47
Branching hyphae multicellular molds
Hyphae and fruiting bodies containing spores | Mycelium: filamentous mass of hyphae
48
Unicellular yeast
Round single cells characterized by budding Reproduce both sexually (spores) and asexually (spores, budding or fragmentation) Resistant to classical antimicrobial drugs
49
Spore cycle
Sporangia burst Spores Spores grow hyphae Sporangia appears
50
Cycle of infection
An infection starts with exposure to the pathogen from either animate or inanimate reservoir
51
Host pathogen interaction
``` Pathogen Reservoir modes of shedding modes of transition portal of entry Host susceptibility ```
52
Pathogenicity
Ability of a microorganism to cause disease
53
Pathogenesis
Biological mechanism(s) that lead to a disease
54
Bacterial pathogenesis
Important to know reservoir of bacterial agents | Disease carrier
55
Convalescent carrier
Those who recovered but continue to shed the pathogen Clinical recovery does not coincide with bacteriological recovery >>> bacteriological surveillance of carrier state is necessary
56
Healthy carrier (subclinical)
Carrier state without clinical symptoms but shedding the pathogen
57
Incubatory carrier
Carrier that is incubating the pathogen but not not yet ill (shedding of pathogen during incubation period)
58
Strangles in horses
Detection of convalescent carriers Highly contagious febrile disease involving upper respiratory tract with abscessation of regional lymph nodes in equines Follow up: 3 negative culture at weekly intervals
59
Virulence
Measurement of pathogenicity
60
Virulence factors
``` Bacterial characteristics that contribute to virulence Physical structures (cell wall, capsule) Chemical substances (toxins, adhesins) ```
61
Pathogenicity islands
Carry genes coding for one or more virulence factors. This group of mobile genetic elements may be located on bacterial chromosome or plasmids and can be transferred through horizontal gene transfer
62
Bacterial transformation
Release of DNA
63
Bacterial transduction
Release of phage
64
Bacterial conjugation
Connected, whole plasma moves over
65
Quorum sensing
the regulation in gene expression in response to fluctuations in cell population density, mediated by chemical signal molecules (autoinducers) Low density: autoinducers diffuse away from bacteria promoting individual cell behavior (doesn't cause disease-invisible) High density: autoinducers bind to receptors and promote group behavior Talk through autoinducers
66
Group behavior
``` Symbiosis Virulence Competence Conjugation Antibiotic production Motility Sporulation Biofilm formation ```
67
Penetration or evasion of host defenses
``` Capsules Cell wall components Enzymes Antigenic variation Invasins Intracellular growth ```
68
Damage to host cells
``` Siderophores Direct damage Toxins (exotoxins, endotoxins) Lysogenic conversion Cytopathic effects ```
69
Adherence and colonization
Flagella Pili/Fimbriae Capsule= glycocalyz, layer of exopolysaccharides -protection from phagocytosis: inhibition of opsonization -Protection from antibiotics
70
Invasion
The ability of the pathogen to spread to other locations in the host, by invading host cells or tissues
71
Extracellular invasion
When bacteria break down barriers of a tissue to disseminate in the host while remaining outside of host cells -production of extracellular enzymes (collagenase, coagulase)
72
Intracellular invasion
When bacteria penetrate cells and survive within this environment - facultative intracellular (listeria) - obligate intracellular (myobacterium)
73
Exotoxins
Exotoxins are generally proteinaceous toxins. The mode of location of toxin delivery affects the clinical symptoms manifested by the infected host Delivery mode -secretion into surrounding millieu -Direct injection into host cell cytoplasm Three major classes
74
Type I Endotoxin
cell surface active Disturbance of cell metabolism Clostridium perfringens Activate second messenger pathways
75
Type II Endotoxin
Membrane damaging Staphylococcus aureus Damage cellular membranes/matrices
76
Type III Endotoxin
Intracellular (A-B toxins) Clostridium botulinum Inhibit protein synthesis
77
Endotoxins
Endotoxin are toxic components of the prokaryotic cell wall that are not released until cell death and lysis of bacteria Effect: fever, diarrhea, weakness, blood coagulation, septic shock and death
78
LPS
Heat stable Lipid A acts as endotoxin Mediator of septic shock Only in gram-negative bacteria
79
(Lipo)Teichoic acid
Mediator of septic shock | Only in Gram-positive bacteria
80
Exotoxin more info
Species: some species of both gram-poitive and gram negative bacteria Protein location: proteins secreted from cell Gene location: usually on plasmids Toxicity: high toxicity Antigenicity: highly antigenic Heat stability:heat labile Vaccine: vaccine available
81
Endotoxin more info
Species: Mostly Gram-negative bacteria and listeria Protein location: part of cell wall Gene location: usually on bacterial chromosome Toxicity: low toxicity Antigenicity: poorly antigenic Heat stability: heat stable Vaccine:no vaccine available
82
Biofilms
Mass of bacteria cling to surfaces, producing extracellular polymer matrix and exchange nutrients
83
Biofilms Function
Bacterial persistence (endocarditis) Reduction of host immunity Local damage (catheters, drinking water pipelines) Reduced susceptibility to antibiotics
84
Iron uptake
Vertebrate tissue is virtually devoid of free iron Iron is needed for bacterial growth Changing the battlefield -bacterial cytotoxins damage host cells- release of ferritin, hemoglobin, lactoferrin -receptor mediated recognition

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