Bacteriology 1: Introduction Flashcards
Three domains of life
Eukarya
Prokaryotes: Archaea & Bacteria
Eukarya
Single-celled or multi-celled organisms enclosed by a membrane.
Archaea
Single-celled microorganisms. Prokaryotes developed separately from bacteria
Bacteria
Single-celled organisms lacking a membrane-bound nucleus and other membrane bounds organelles.
**Smaller and less complex than eukarya.
Characteristics unique to bacteria
-Rigid cell walls with PEPTIDOGLYCAN
- No membrane bound organelles
-No nucleolus, mitochondria, ER, or golgi
-Multiply by binary fission
-Usually <5 micrometers
Bacteria (prokaryotes) Vs Eukaryotes
See image
Bacteria Classification categories
-Morphology
-Biochemical reactions
-Serology
-Nucleic Acid profiles
Bacterial morphology
Rods vs Cocci
Bacterial Ultrastructures
Structures that have potential to make bacteria infectious
- Cell envelope
- Cytoplasm
-Other: Flagells, Pili, Spores, Biofilm
Cell envelope structures
- Capsule or Slime layer (+/-)
- Cell Wall
- Cytoplasmic membrane
Cytoplasm Structures
Nucleoid
Ribosomes
Capsule and Slime layer.
What is it? What is the function?
Gelatinous material lying outside the cell wall (Goop)
- Carbohydrates
- Sometimes polypeptides (Sticky goop)
- Very variable (antigenically diverse)
- Function: help adherence, anti-phagocytic, prolong survival in the environment
Cell wall
What is it? What does it influence?
-Gives bacteria shape and rigid structure, ~20% of bacteria dry weight.
-Different structures and chemical composition influences the pathogenicity and staining characteristics
Types of bacteria/Staining methods
Gram positive
Gram negative
Acid fast
Gram staining
Fixation
Crystal violet (gram positive)
Iodine treatment
Decolorization
Counter stain with safranin
Gram staining types of damage affecting outcome
Heat
Age
Antibiotics
** All damage the peptidoglycan cell wall **
Gram Negative cell wall structure
Thin peptidoglycan cell wall that is also surrounded by an outer membrane containing lipopolysaccharides and porins.
Gram Positive cell wall structure
Lack an outer membrane but are surrounded by layers of peptidoglycan
Porins
Porins are pore proteins contained in the outer membrane of Gram-negative bacteria and they mediate the diffusion of small hydrophilic molecules. Thus allow in antibiotics
Lipopolysaccharides
provide structural integrity and a permeability barrier to protect the bacterial cell from the entry of deleterious molecules such as toxins and bile salts during its inhabitation in the gastrointestinal tract
Gram-Neg vs Gram-Pos cell wall composition
See image
Why do we care Gram-Neg or Gram-Pos?
- Help with diagnosis
- Some ABX are effective with only one or the other
- Few ABX are broad to both
- Antimicrobial therapy is most effective when it is narrow spectrum!!!
Gram-Pos bacteria
Characteristics?
Staining qualities?
-Simpler than Gram-neg
-Thicker more uniform cell wall, composed of peptidoglycan and teichoic acid
-More resistant to mechanical damage
-Peptidoglycan is target for ABX and lysozyme
- Neutralized by detergents
-Retain Crystal violet staining through decolorization process causing cells to appear PURPLE/BLUE
Gram-Neg bacteria
Characteristics?
Staining qualities?
- More complex than gram pos
-Outer-membrane has LPS. MAJOR virulence factor
-Periplasmic space with small amount of peptidoglycan - Outer-membrane excludes hydrophobic molecules rendering them resistant to detergents
What is a detergent?
water-soluble cleansing agent which combines with impurities and dirt to make them more soluble
Acid Fast bacteria
Characteristics?
Staining qualities?
Additional molecules/fuction?
-Cell Envelope contains additional molecules.
— Mycolic acid, glycolipids, fatty acids, and polypeptides
- Additional molecules makes staining difficult
-Additional molecules allows them to survive in the environment and survive inside cells
-Additional molecules can be a target for certain ABX
Flagella
Important for motility
Fimbriae (pili)
Important for adherence
Spores
Inactive form of bacteria. Important for long term survival and physical resistance
States bacteria may exist in
Planktonic (Free)
Sessile (attached)
What is a biofilm? How does it act?
Some bacteria create this to exist in sessile form.
- Biopolymer matrix enclosing a population of bacteria to each-other and/or a surface
-Acts as an organism through “quorum sensing”
Biofilm “quorum sensing”
Activates biofilm creation when planktonic bacteria numbers are high and activates biofilm degradation when planktonic bacteria numbers are low
How do biofilms help in the pathogenesis of bacteria?
-Aid colonization
-Avoid phagocytosis
-Avoid antibiotics
What is in bacterias cytolasm?
Ribosomes
Granules
Nucleoid
What is a bacterial nucleoid and what does it contain?
An irregularly shaped region in a prokaryotic cell that contains most of the genetic material.
Also contains: plasmids and phages
How do bacteria increase in numbers?
-Binary fission
What is generation time and what influences it?
Length of time required for a single bacterium to yield two daughter cells.
- Genetics (type of bacteria)
-Nutritional factors (nutrient media)
-Chemical and physical and environmental factors
Define clonal expansion and what it represents for bacterial growth
- Clonal expansion is the binary fission of a bacterium into a colony.
-Small colony = slow growing/long generation time
-large colony = fast growing/short generation time
Optimal conditions for bacterial growth
pH: neutral to alkaline
Tonicity: isotonic
Temperature: 98.6. (Range: 68 -113)
— Listeria = cold 39
Atmospheric condition: vary
Categories of atmospheric requirements of bacteria
Strict aerobes: Require O2
Strict anaerobes: Killed by O2
Facultative anaerobes: Grow with/without O2
Microaerophiles: Require reduced O2 (<20%) and some like increased CO2
What is important to know the atmospheric conditions of bacteria?
- types and location of diseases they can cause
- Your approach to diagnosis of these infection
- How to treat
What are the genetic elements of bacteria?
- Bacterial genome
- Plasmids
- Bacteriophage
Types of bacterial genomes?
- Haploid, circular chromosome (1n)
-Diploid, double stranded DNA
What are plasmids?
Small circular DNA which can autonomously replicate. May encode virulence (toxin) and ABX resistance.
May be stand alone or integrated into bacterial genome
May transfer from one bacteria to the next
What are bacteriophages
Viruses which infect bacteria.
-Usually integrate into the bacterial genome but may stand alone.
-May encode virulence genes
Bacterial variation
Due to either phenotypic variants or genotypic variants
Bacterial genotypic variants
- Mutation
- Recombination
- Transposition
Bacterial genotypic variants- mutations
Change in chromosomal DNA
Bacterial genotypic variants- Define Recombination. List possible ways.
Exchange of DNA between Bacteria
1. transduction: Phage mediated transfer
2. conjugation: plasmid mediated transfer
3. Transformation: uptake of naked segment of DNA
What do genotypic variants usually lead to?
Morphological changes
Virulence
Where on the body is strictly anaerobic?
surface of epithelium:
- Lumen of GI tract
- Btwn teeth and gums
- Urogenital tract
Bacterial genotypic variants- Transposition
Relocation of parts of DNA in the genome mediated by transposable elements
When do we have strictly anaerobic tissues?
If necrosis is present
