Microbiology - Edwards Flashcards
Difference bn prookaryotic + eukaryotic cell
Prokaryotes:
- much smaller
- often single celled
- single circular chromosome
- introns are rare
- 70s ribosomes
- rigid cell walls
- rapid cell cycle
Eukaryotes:
- complex, compartmental
- frequently multicellular
- linear chromsome + histones
- introns/exons
- 80s ribosomes
- flexible cell wall
- cell cycle, mitosis/meiosis
Gram +
- rich, thick, peptidoglycan cell wall
(hence can stand bigger osmotic pressures) - no outer membrane
- no LPS , bc no outer membrane
- no periplasmic space
Gram -
- peptidoglycan is reduced
- has an additional outer membrane
- often the additional outer membrane is decorated with LPS
** LPS referred to as ENDOTOXIN + linked to SEPSIS/SEPTIC SHOCK
** Antigen + Endotoxin + B cells + Inappropriate immune response
- has periplasmic space
v thin cytoplasmic cell wall
EXAMPLES:
- neisseria spp (STD/STI + meningitis)
- escherichia coli (GI tract)
Bacterial growth + requirements
Prokaryotic Growth
- NUTRITION
- TEMPERATURE
- HYDROGEN ION CONCENTRATION
human commensals - approx 7 pH - OSMOTIC PROTECTION
human commensals - approx 0.85% NaCl
BACTERIAL GROWTH CURVE
- lag phase
- exponential growth phase
- stationary phase
- decline phase
TB
- bacterium Mycobacterium tuberculosis
- primarily affects the lungs but can also spread to other parts of the body, including the brain, kidneys, spine, and lymph nodes
- spreads through the air when an infected person coughs, sneezes, or talks, releasing droplets containing the bacteria
- Persistent cough (lasting three weeks or longer), sometimes with blood-tinged sputum.
- Chest pain.
- Fever.
- Night sweats.
- Weight loss.
- Fatigue.
- Loss of appetite.
Protozoa
single/multi?
living? non-living?
euk/prok?
single celled
eukaryotes
Fungi
single/multi?
living? non-living?
euk/prok?
eukar
Bacteria
single/multi?
living? non-living?
euk/prok?
single celled
PROKARYOTES
Viruses
single/multi?
living? non-living?
euk/prok?
non-living
obligate parasites
Viruses are neither prokaryotic or eukaryotic. Viruses are not made of cells. Viruses cannot replicate on their own. Most scientists do not consider viruses to be livingm
Obligate parasite = a parasitic organism that is not able to complete its life cycle without exploitation of suitable host
microbiome
collection of microorganisms, including bacteria, viruses, fungi, and protozoa, along with their genetic material, that live in a specific environment, such as the human body or a natural habita
microflora / microbiota
community of microorganisms, including bacteria, fungi, viruses, and protozoa, that live on or within different parts of an organism, such as the human body, plants, or animals. These microorganisms a
Difference in cell structure bn eukaryotes + prokaryotes
Eukaryotes:
- Cell membrane
* Nucleus
* Centriole/Centrosome
* Nucleolus/Ribosomes
* Endoplamsic Reticulum (ER)
* Cytosol
* Mitochondria
* Golgi
* Cytoskeleton
* Secretory Vessicles, Lysosomes
Prokaryotes:
- Plasma Membrane
* Cell Wall (Peptidoglycan)
* Nucleoid (DNA & associated proteins)
* Ribosomes
* Cytoplasm
* Capsule, Flagellar, PiliF
Fermentation VS Anerobic respiration
both processes used by cells to generate energy in the absence of oxygen
Fermentation
energy is produced by breaking down glucose (or other organic molecules) into smaller compounds without using the electron transport chain or an external electron acceptor.
○ Involves glycolysis only. ○ Pyruvate or its derivatives act as the final electron acceptors. ○ Produces a small amount of ATP (2 ATP per glucose).
END PRODUCTS:
○ Alcohol fermentation: Produces ethanol and CO₂ (e.g., in yeast).
○ Lactic acid fermentation: Produces lactic acid (e.g., in muscle cells under low oxygen).
common in:
- yeast
- bacteria
Anaerobic respiration
A process that uses an electron transport chain to generate ATP, with a molecule other than oxygen (e.g., nitrate, sulfate, or carbon dioxide) serving as the final electron acceptor.
○ Includes glycolysis, the Krebs cycle, and an electron transport chain. ○ Uses inorganic molecules like nitrate (NO₃⁻) or sulfate (SO₄²⁻) as the terminal electron acceptor instead of oxygen. ○ Yields more ATP than fermentation but less than aerobic respiration (e.g., 20-30 ATP per glucose).
END PRODUCTS
-> Depends on the final electron acceptor. Examples:
§ Nitrate reduction produces nitrogen gas or ammonia.
§ Sulfate reduction produces hydrogen sulfide.
common in:
- some bacteria
- archaea
Peptidoglycan cell wall
in bacteria
structure
peptide side chain:
- D-Ala-D-Ala
- Transpeptidation
repeated sugar chains:
- transglycosylation
Target of PENICILLIN
DD-Transpeptidase, a bacterial enzyme that cross-links the peptidoglycan chains to form rigid cell walls
Flagella + Fimbriae
present in both Gram - and + bacteria
injection of toxins + genetic material
adherence, sex, motility
Syphilis
an infection caused by bacteria. Most often, it spreads through sexual contact. The disease starts as a sore that’s often painless and typically appears on the genitals, rectum or mouth.
E.Coli
Facultative Anaerobs
Organisms that can survive and grow in both oxygen-rich (aerobic) and oxygen-poor (anaerobic) environments.
Metabolism:
Prefer aerobic respiration when oxygen is available because it yields more ATP.
Switch to anaerobic respiration or fermentation in the absence of oxygen.
Examples: Escherichia coli, Saccharomyces cerevisiae (yeast), and many species of Staphylococcus.
Obligate Anaerobes
Organisms that cannot survive in the presence of oxygen. Oxygen is toxic to them due to the lack of protective enzymes (e.g., catalase, superoxide dismutase).
Metabolism:
Use anaerobic respiration or fermentation to generate energy.
Oxygen exposure can lead to the production of harmful reactive oxygen species (ROS).
Examples: Clostridium botulinum, Bacteroides fragilis, Methanogens.
Environment: Found in oxygen-free environments, such as deep soil, intestines, or anaerobic chambers.
diagnostic approaches to identify prokaryotic pathogens
MOLECULAR TESTS:
- antigens (immunological)
- DNA sequencing 16sRNA, qPCR
- protein profiling (mass spec)
METABOLIC TESTS:
- Haemolysis (strepoccocci only) -> destruction of red blood cells
- catalse test/coagulase
GROWTH REQUIREMENTS:
- aerobic/anaerobic
- requirement for blood products (e.g. serum proteins)
- sensitivity to agens (bile / NaCl)
APPEARANCE
- shape
- size
- cell wall (Gram +/-)
Gram stain classification
Retention of crystal violet/iodine complex by Gram+ bacteria
distinguishing Gram + and Gram - bacteria according to cell wall structure
stain with crystal violet and rinse:
+ = purple
- = purple
treat with gram’s iodine:
+ = crystal/violet iodine complex
_ = ‘’ ‘’
briefly decolorise with acetone:
+ = purple
- = no colour
counter stain with basic safranin, pink dye, rinse
+= purple
- = pink
** TB , myocobacterium tuberculosis will NOT stain, has lipid rich cell wall
** Treponema will NOT stain
spore + toxin