Basic Bacteriology Flashcards
1
Q
What are the characteristics of Bacteria?
A
- Simple unicellular prokaryotes
- Prokaryotes lack membrane-enclosed organelles
2
Q
What is a bacteria’s cell wall made from?
A
Peptidoglycan
3
Q
How do bacteria reproduce?
A
Binary fission
4
Q
What is the process of Binary Fission?
A
- Cell replicates its DNA
- The cytoplasmic membrane elongates, separating DNA molecules
- Cross wall forms; membrane invaginates
- Cross wall forms completely
- Daughter cells
5
Q
What are the Characteristics of Fungi and how do they reproduce?
A
- Diverse group of organisms; molds, mushrooms, yeasts
- Reproduce asexually or sexually
6
Q
What are the characteristics of Protozoa?
A
- Single-celled eukaryotes
- Diverse group of organisms:
- Vary in size, shape, features and habit
7
Q
What are the characteristics of Viruses and how do the reproduce?
A
- Acellular
- have DNA or RNA core, surrounded by a protein coat
- coat may be enclosed in an envelope
- have DNA or RNA core, surrounded by a protein coat
- Only seen with electron microscope
- Reproduce only in host cell by using its cellular machinery
8
Q
What are the differences between Prokaryotic Cells and Eukaryotic Cells?
A
-
Prokaryotic Cells
- Smaller, um
- No true nuclear membrane
- Haploid
- Circular DNA
- Can exist independently in nature or in many environments
- Ubiquitous in nature
- Asexual
-
Eukaryotic Cells
- Larger
- True nucleus
- Membrane enclosed organelles
- Linear DNA
- Diploid
- Can reproduce sexually
- Increased genetic diversity
9
Q
Compare Gram Positive and Gram Negative Bacteria
A
-
Gram Positive
- Thick cell wall
- Inner membrane
- Break cell wall, immediate cell death
-
Gram Negative
-
Double membrane
- Thin cell wall, inner and outer membrane
-
Double membrane
10
Q
What are the characteristics of Spores?
A
- Thick-walled, differentiated structure
- Highly heat, radiation, chemical and dessication resistant
- Commonly isolated from soil
- Bacteria can endure nutrient depletion, harsh conditions and facilitate dispersal in the enviornment, wind, water and animal GIT
11
Q
What is glycolax?
A
A substance that surround bacterial cells
- Capsule: if organised and firmly attached to cell wall
- Slime layer: if unorganised and loosely attached to cell wall
12
Q
Describe the characteristics of the Capsule
A
- Dense, well-defined polysaccharide or protein layer closely surrounding a cell
- More resistant to physical and chemical agents and antibiotics
- Facilitate adherence to host cells and surfaces (biofilms)
13
Q
What are the characteristics of Flagella?
A
- Long, thin cellular appendage, capable of rotation in prokaryote cells and responsible for swimming motility
14
Q
What are the characteristics of Exotoxins?
A
- Proteins produced more commonly inside gram-positive bacteria, as part of their own growth and metabolism
- Exotoxins are then secreted or released into the surrounding medium following lysis
15
Q
What is one of the most potent endotoxin known?
A
Clostridium Botulinum
16
Q
What are the Characteristics of Clostridium Botulinum and what symptoms do they produce?
A
- Gram positive rod; anaerobic
- Form heat resistant spores
- Produce very potent neurotoxins
- Symptoms:
- Initial: Nausea, vomiting, cramps, diarrhoea
- Neurological symptoms: Flaccid paralysis, death
17
Q
What are the clinical applications of botulinum toxin?
A
- Botox treatment
- Therapeutic agent
- Blepharospasm
- Muscle spasms
- Migraine headaches
- Excessive underarm sweating
18
Q
What are the Characteristics of Endotoxins?
What symptoms does it cause?
A
- Lipid portions of lipopolysaccharides (LPSs) that are part of the outer membrane of the cell wall of gram-negative bacteria
- The endotoxins are liberated when the bacteria die and the cell wall breaks apart
- Causes fever, low blood pressure, inflammation
- Responsible for dramatic effect of Neisseria meningitidis
19
Q
What are the phases of the bacterial growth curve?
A
- A: Bacteria gets used to environment
- B: Amount of bacteria increases exponentially
- C: Amount of bacteria generated similar to the amount that die
- D: Death
20
Q
What are the Factors Influencing Bacterial Growth?
A
- Temperature
- pH
- Water availability and osmotic pressure
- Oxygen availability
21
Q
Describe the inflence of temperature on bacterial growth
A
- Minimum: Membrane gelling; transport processes so slow that growth cannot occur
- Maximum: Protein denaturation; collapse of the cytoplasmic membrane; thermal lysis
22
Q
What is the optimum pH for bacterial growth?
A
- 7.2-7.6
23
Q
What is an extremophile?
A
- An organism that grows optimally under one or more enviornmental extremes
24
Q
What is a culture medium?
A
- Aqueous solution of various nutrients suitable for the growth of microorganisms
25
What are the nutritional requirements for the laboratory culture of microbes?
* Macronutrients: carbon source, nitrogen, potassium, sulphur e.t.c
* Micronutrients: trace elements e.g. boron, chromium, iron e.t.c
26
What culture media are used in laboratory culture of microbes?
* Liquid
* Solid: gelling agent usually agar added
27
Describe Chemically Defined Culture
* Exact chemical composition known
* General Purpose Complex: nutrient/blood agar e.t.c
28
Describe Differential Culture
* Contains indicators such as pH indicators or chromogens to identify target organism
29
Describe Selective Culture
* Combination of chemicals and antibiotics to select target bacteria
* Suppresses normal flora or contaminating bacteria
30
Describe Selective and Differential Culture
* MacConkey Agar (Mac)
31
What are the Steps when Culturing Bacteria?
* Inoculation
* Incubation
* Isolation
* Inspection
* Identification
32
Describe the Process of Inoculation
* Producing a culture
* Introduce a tiny sample (the inoculum) into a container of nutrient medium
33
What is the purpose of Culturing Bacteria?
* Used to manipulate, grow, examine and characterise microorganisms in the lab
34
Describe the Process of Incubation
What are the Types of Culture?
* An inoculated sample is placed in an incubator to encourage growth at optimal temperature
* 18°C-37°C
* Can control atmospheric gases e.g. CO2
* Can recognise growth as turbiditiy in liquid media and colonies on solid media
* Type of culture:
* Pure culture: growth of only a single known species (also called axenic)
* Mixed culture: two or more species
* Contaminated culture: includes unwanted microorganisms of uncertain identity or contaminants
35
What is the process of Isolation?
* Separating one species from another
36
What are the Steps involved in Inspection and Identification?
a. Appearance
b. Metabolism - biochemical tests
c. Genetic analysis - PCR
d. Protein Profile - mass spectrometry
37
Describe Appearance in Inspection and Identification
* Microscopy
* Observe unstained wet mount of bacteria
* Determine size and shape of bacteria
* Motility
* Stained preparations
* Bacteria fixed to slide by heat or alcohol
* Differential stain used:
1. Gram Stain: +ve or -ve
2. Add fast stain: to check for acid fast bacteria
3. Spore stains, flagella stains, capsule stains
38
Describe Metabolism in Inspection and Identification
* Biochemical tests
* e.g. nitrate broth, catalase
39
Describe Genetic analysis in Inspection and Identification
* PCR
* PCR to distinguish MRSA from MSSA
* Separate DNA and Stain
40
Describe Protein Profile in Inspection and Identification
* Mass spectrometry
* Separates proteins on their size; give proteins at peaks
* Can't tell you if resistant or not
