Introduction to Microbiology, Microbiological Concepts & Biochemistry of Microbes Flashcards
Which doctor first used handwashing to reduce clinical infection?
Ignaz Semmelweis
In 1870, which doctor was the first to use antisepsis for surgery?
Joseph Lister
What is abiogenesis and who disproved that this is how infections start?
Abiogenesis is the theory of spontaneous generation. Louis Pasteur was able to disprove this
Which scientist first demonstrated that microorganisms caused infectious disease? What two diseases did this person study in the process?
Robert Koch demonstrated that microorganisms caused infectious disease through his Germ Theory of Disease (Koch’s Postulates). In the process, he studied anthrax and tuberculosis
What is a pure culture?
A population of a certain type of cells that are cultured and grow separately from any other type of cell
List Koch’s Postulates
- The specific causative agent must be found in every case of an infectious disease
- This agent is taken and cultured purely
- A sample is inoculated and transferred to a healthy, susceptible animal. This must cause the same infection.
- The microbe is extracted from the infected animal
Three domains of life
- Eubacteria
- Archea
- Eucarya
Principle members in eubacteria
- Gram positive bacteria
- Gram negative bacteria
Principle members in eucarya
- Protozoa
- Algae
- Fungi
What is the main difference between eukaryotic and prokaryotic cells
Eukaryotic cells have a nucleus, prokaryotic cells have no nucleus
Key features of algae
- Eukaryotic
- Photosynthetic
- Unicellular or multicellular
Three motility mechanisms for protozoa
- Cilia
- Flagella
- Psuedopodia
Are fungi eukaryotic or prokaryotic?
Eukaryotic
How do fungi differ from plants and animals?
- Differ from plants as they do not use photosynthesis for energy
- Differ from animals as they have a cell wall
Name the two different types of fungi and how they differ to each other
Moulds: multicellular, reproduce through spores (sexually and asexually)
Yeasts: unicellular, reproduce by budding (asexually)
The cell wall of bacteria contains polysaccharide and peptidoglycan, true or false?
True
Name the two structures that make up all viruses
- Nucleic acid (DNA/RNA)
- A protein coat (capsid)
Viruses that infect bacteria
Bacteriophages
Harmless microorganisms
- Around 87% of microorganisms are harmless
- These organisms are helpful and have an important role in the food chain
- e.g. decomposition, nitrogen fixation
Opportunistic microorganisms
- 10% of microoganisms are opportunistic
- Microbes that are usually harmless but can be pathogenic when placed in different conditions
- e.g. bowel flora that find their way to the bladder
Harmful microogranisms
- Around 3% of microogranisms are overly harmful
- Can cause disease when present in the body and upon initial contact with a healthy person
- e.g. tapeworm, syphilis
Normal flora
- Microbes that naturally inhabit surfaces of the human body
How can there be a greater microbial load in the body comparing to the number of cells in the body?
- Total microbe load >10^3
- Total cells in the body is 10^3
- This is possible as microbes are much smaller than body cells
Eukaryotes
- Fungi, algae and plants (simple cell wall)
- Protozoa and animals (no cell wall)
- Nucleus and nuclear membrane
- Larger ribosomes
- Larger than prokaryotes (10 - 100 micrometres)
- Reproduce by mitosis/meiosis
Prokaryotes
- Archaea and bacteria
- Smaller than eukaryotes (0.1 - 10 micrometres)
- No nuclear membrane or nucleus
- Complex cell wall (with peptidoglycan for bacteria/eubacteria)
- Smaller ribosomes
- Reproduce by binary fission
Louis Pasteur
- Disproved theory of spontaneous generation (abiogenesis)
- Discovered pasteurisation (originally used to prevent spoilage of wine)
Robert Koch
- First to study anthrax and tuberculosis
- Koch’s postulates
- Contributed to develop staining methods for microbes
Robert Hooke
- First person to describe a cell
Joseph Lister
- Credited with developing antisepsis for surgery
Antoni van Leeuwenhoek
- First to describe bacteria including their shapes
- Reported existence of protozoa two years before
- Bacteria took longer to discover as work was still being done on his microscope, and bacteria are a lot smaller than protozoa
Ignaz Semmelweis
- First to use handwashing in clinical practice
Bacteria
- Do not have a nuclei
- e.g. Escherichia coli
- Prokaryotic
Algae
- Eukaryotes
- Photosynthetic
- Can be unicellular or multicellular
Protozoa
- Single celled eukaryotes
Fungi
- Have a cell wall
- Not photosynthetic
- Two types: moulds and yeasts
Moulds: multicellular, reproduce sexually and asexually (spores)
Yeasts: unicellular, reproduce asexually (budding)
Viruses
- Can only be seen with an electron microscope
- Cannot reproduce independently, must reproduce inside a host cell
Bacteria cell wall composition (gram positive)
- Thick layer of peptidoglycan
- Teichoic acid and lipoteichoic acid
Bacteria cell wall composition (gram negative)
- Thin layer of peptidoglycan
- Outer membrane contains lipopolysaccharide
Glycocalyx
- A gelatinous material which coats the surface of some bacteria
- Capsules and slime
Capsules
- Highly organised
- Well attached
- Protect against phagocytosis
- e.g. H. influenzae B
Slime
- Not highly organised
- Not well attached
- Helps bacteria to slide on surfaces
- Protect bacteria from drying
- Can be washed off easily
Flagella, fimbriae and pili
- Flagella: motility
- Fimbriae: adherence
- Pili: adherence and conjugation (passing DNA from one organism to another)
Difference between gram positive and gram negative bacteria
- Differences in the structure of their cell wall
Steps of a gram stain
- Spread bacteria across a slide with water
- Heat fix the slide
- Stain with crystal violet (30 sec)
- Stain with iodine (30 sec)
- Discolour with alcohol
- Stain with carbol fuschin (30 sec)
How bacteria grow
- Binary fission
- Single cell splits into two identical daughter cells
- Chromosome duplicates, same genetic material in both cells
Stages of bacterial growth in broth solution
- Lag phase
- Exponential phase
- Stationary phase
- Death/decline phase
Obligate anearobe
- An atmospheric condition
- Where bacteria is unable to grow in O2 and will only grow in the complete abscence of O2
Facultative anearobe
- Atmospheric condition where bacteria is able to grow with or without O2
Carboxyphile
- Atmospheric condition where bacteria grows best with an increased concentration of CO2
Mesophile
- An organism which grows best in moderate temperatures (optimum 37 degrees)
Psychrophile
- An organism which grows best in cold temperatures (optimum 15 degrees)
Glycolosis
- Occurs in all cells
- Anaerobic process (no oxygen required)
- Consists of 10 reactions
- For every molecule of glucose, there is a net gain of 2 ATP and 2 molecules of pyruvic acid produced
Respiration
- Obligate aerobes and facultative microbes (oxygen required)
Krebs Cycle
- Consists of 8 reactions
- Utilises pyruvic acid
- 2 ATP molecules produced
- CO2 produced
Electron Transport Chain
- Many redox reactions
- Many ATP molecules produced
- H2O produced
Fermentation
- Obligate anaerobes and facultative microbes (no oxygen)
- Utilises pyruvic acid
- Not as much ATP produced
- Organic wastes (acids and alcohols) produced
Catabolism
- Larger molecules broken down into smaller molecules
Anabolism
- Smaller molecules built up into larger molecules
Oxidation
- Loss of electrons
Reduction
- Gain of electrons
What factors (growth & nutritional conditions) need to be considered when culturing bacteria?
- Temperature preferences (whether they grow best in cold temperatures or warm temperatures)
- Atmospheric conditions (whether they can grow with oxygen, without oxygen, with more CO2 etc.)
- Moisture
- pH
- Osmolarity
- Nutrients
Microbial biofilm
- Composed of a complex mixture of microbes, cell debris and extracellular matrix
- Found on natural, wet surfaces
- Matrix is made of an extracellular slime layer
How plaque leads to tooth decay
- Sucrose in the diet is degraded by bacteria to produce acids
- Build up of plaque»_space; higher numbers of bacteria»_space; greater production of acids»_space; more demineralisation in teeth
Virulence factor
- Traits that give a microbe the ability to cause disease
- Endotoxins and exotoxins
- Production and release of enzymes
- Production of hameolysins
- Production of adherence factors (fimbriae, pili, glycocalyx)
Difference between endotoxin and extotoxin
- Endotoxins come from gram negative bacteria
- Exotoxins come from gram positive bcteria
- Endotoxins are within the cell wall
- Exotoxins are inside the cell
- Endotoxins are released when the cell dies and the cell wall breaks up
- Exotoxins are released and secreted by the living cell
Three types of haemolysis
- Alpha: partial lysis around colonies (green/grey colour)
- Beta: complete lysis
- Gamma: no haemolysis
Functions of parts of a light microscope
- Condenser: focuses light through the specimen
- Diaphragm: controls the amount of light going through the condenser
- total magnification = objective size x occular size
How would you increase contrast when looking at an unstained preparation with bright field
illumination?
- For unstained specimens, contrast can be increased by closing the condenser diaphragm
Selective and differential media
- Selective media only allow certain bacteria to grow while inhibiting others
- Differential media contain substances that will allow different bacteria to be distinguished
from each other
Four principle shapes of bacteria
- Bacillus (rods)
- Coccus (round)
- Spirals
- Vibrio (comma shaped)
Four principle types of microscopic arrangement
- Diplococcus (pairs)
- Chains
- Clusters
- Single cells
Apart from colony morphology and the Gram stain, what other methods could be used to identify an
unknown organism?
- Serotyping & detection of virulence factors (e.g. demonstration of specific enzymes)
- Using molecular techniques
- Observing biochemical characteristics
What is the difference between the incubation period of a disease and the invasive phase?
Incubation:
- No symptoms
- The initial invading microbes invade body
- They must overcome the host’s defences (e.g. skin, immune system)
Invasive:
- Identifiable disease with dramatic increase in microbes (may continue to
death)
Microaerophile
- A microorganism that requires oxygen to survive, but these levels must be lower than what is present in the atmosphere
Mutualism
- Symbiotic relationship where both members benefit
Commensalism
- Symbiotic relationship where one member
benefits without affecting the other
Parasitism
- Relationship where
one member benefits while the other is harmed - also called amensalism or antagonism
