Microbiology Flashcards
What is the name of the first oxygen producing micro-organisms?
Cyanobacteria
What 3 things is all life classified as?
Bacteria, Archaea, Eukarya
What was Pasteurs hypothesis?
Microorganisms present in putrefying material were descendants of those already present in the material or that were are carried in on dust particles in air
Knowledge that life does not arise spontaneously allows?
- Prevention of food spoilage
- Prevention of infections during operations
- Understanding of the causes of infectious diseases
Who helped in the prevention of food spoilage and when?
Louis Pasteur (fermentation, pasteurisation) 1864
Who helped in the prevention of infections during operations?
Lister (aseptic technique) 1867
Who helped in the understanding of the causes of infectious diseases?
Koch (Germ theory of disease & Koch’s postulates) 1876
What experiment was defined as definitive proof for biogenies?
Swan neck flask
What were Koch’s postulates?
- The suspected pathogen must be present in all cases of disease and absent from healthy animals
- Suspected pathogen must be grown in pure cultures
- Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal
- The suspected pathogen must be reisolated and shown to be the same as the original
What did Hooke do?
First observed “cells”
What did Van Leeuwenhoek do?
Observed live micro-organisms
How did Karl Woese discover archaea?
He looked at the ribosomal DNA and recognised it was very different to that of bacteria
Features of a bacterial cytoplasm.
- Thick, semi-transparent and elastic
- 80% water
- Contains all the molecules required for life
Features within the bacterial cytoplasm.
- The nucleiod (DNA)
- Ribosomes (site of proteins synthesis composed of RNA and protein
Features of a bacterial cell membrane.
- A thin structure inside the cell wall and enclosing the cytoplasm
- Consists of a phospholipid bilayer
- Contains selective carrier proteins
- Acts as a semi-selective barrier that regulates the uptake of nutrients
Features of bacterial cell wall.
- Very rigid to protect cell from rupturing
- Antigenic, often contains toxic molecules and is a common site for antibiotic action
- Two types differentiated by gram stain
How is the strength of a bacterial cell wall provided?
A mucopeptide called peptidoglycan which is unique to bacteria
Composition of cell wall in gram negative bacteria from inside to outside
Cytoplasm, Inner membrane, Cell wall, Outer membrane, Lipopolysaccharide (LPS)
Composition of cell wall in gram positive bacteria from inside to outside
Cytoplasm, Inner membrane, Cell wall, Teichoic Acids
What do lipopolysaccharides do?
Otherwise known as endotoxin. Important virulence factor for evading phagocytosis and a barrier to certain antibiotics
What is teichoic acid?
Long anionic polymers that thread through the thick, multi layer of highly cross-linked peptidoglycan.
Describe the capsule of a bacteria
Firmly attached and highly organised
Describe the slime layer of a bacteria
Unorganised and loosely attached
What do flagella do?
Help a bacteria move by rotation
Describe flagella
Long whip like structure required for motility
3 Components of flagella
- Long spiral filament made of many proteins including flagellin and acts as a propeller
- Attached to a hook which can transmit torque
- Attached to motors that drive their rotation
What protein is the filament made of?
Flagellin
Structure of pili/fimbriae
Hair-like appendages, shorter, stronger and thinner than flagella
Functions of pili.
- Involved in forming biofilms and attachment of cells
- Used for DNA transfer, called conjugation
What is an endospore?
A dormant form of the bacterium which is highly resistant to adverse environmental conditions
What is a broth and its purpose?
A liquid media
For enrichment of certain bacteria, obtaining large numbers of bacteria and for performing growth curves
What is agar and its purpose?
Solid media:
- Usually first step of bacterial identification
- Observe the colonial morphology which aids ID
- Assess purity of the culture
What is sloppy agar and its purpose?
Semi-solid agar
- Demonstrating mobility
- Preserving bacteria
What are the 5 steps of staining for gram +/-
- Fixation
- Crystal violet
- Lugol’s iodine
- Decolourisation
- Safranin
What are the end colour results for gram +/- staining?
Gram positive - purple
Gram negative - pink
Structure of filamentous fungi
- Consist of hyphae
- Some hyphae contain cross walls (septa) which divide them internally into distinct uni-nucleate units
What is hyphae?
Thin, thread-like filaments
Structure of non-filamentous fungi
Unicellular, round or oval cells
What is dimorphism?
The ability of a fungus to exist in both morphological forms
What are heterotrophs?
They don’t make their own food, they obtain their nutrients from pre-formed sources of organic carbon
Fungi are heterotrophs
What are saprotrophs?
Primary decomposers
Fungi are saprotrophs
What do fungi store food as
Glycogen
3 mechanisms of asexual reproduction in fungi
- Hyphae fragmentation
- Spore production
- Budding (only in yeast)
3 examples of fungi as a pathogen
- Superficial infections (dermatomycoses)
- Subcutaneous fungal infections
- Systemic mycoses
What are superficial infections with examples?
Also referred to as dermatomycoses, it’s infections of the outer layer of the skin, the hair and nails
Examples = athletes foot, ringworm
What are subcutaneous fungal infections?
Infections that usually occur in deeper layers of the skin and sometimes even reach the underlying bone
Examples = chromoblastomytosis and mycetoma
What is systemic mycoses?
Infection that often occurs via the inhalation of spores in individuals with weakened immune systems
Examples = Thrush and histoplasmosis
Describe fungi as a symbiont : mycorrhizae
- Mutualistic relationship between fungus and plant root
- Fungus functions like a root by growing in the soil and absorbing nutrients while the plant provides it with sugar for energy
Properties of ectomycorrhiza
-Common in temperate forest ecosystems
-Fungus - ascomycota and basidiomycota
Between root cells
Properties of Arbuscular mycorrhiza
- Common in grasslands and tropical ecosystems
- Fungus - zygomycota
- Invades root cells
Describe fungi as a symbiont : Lichens
- First forms of life to colonise bare rocks/soil
- Acts as barometer for air quality - change in lichens = change in pollution
What is chimera and explain this is protozoa
Derived from two or more genetically different types
Protozoa are formed from two prokaryotes and kept the characteristics of them both
Give examples of how protozoa are hard to classify
- The genus Euglena has chloroplasts and flagella
- Giardia have two nuclei and no mitochondria
- Entamoeba have many nuclei and no mitochondria
What are the 4 main groups of protozoa and what are they characterised by?
- Ciliates
- Apicomplexa
- Flagellate
- Amoebae
Characterised by : movement, nutrition and reproduction
What do microorganisms need energy for?
- Grow and move
- Reproduce
- Maintain cell structures
- Defend themselves against threat
What are the by products of anaerobic respiration?
Lactate and acetaldehyde (then to alcohol)
What is an obligate aerobe?
Cannot survive without oxygen
What is a facultative aerobe?
Primarily anaerobic but can respire using oxygen
What is a obligate anaerobe?
Cannot grow in the presence of oxygen (vegetative cells)
What is a facultative anaerobe?
Primarily aerobic but can respire anaerobically
What is a microaerophillic organism?
Required oxygen but can only tolerate a small amount
What is the main source of carbon?
Atmosphere and organic compounds
What is an autotroph?
An organism that produces its own food using light, water, CO2/ other chemicals
How does an autotroph acquire carbon?
Via CO2
What is a heterotroph?
An organism that eats other plants or animals for food or energy/nutrients
How do heterotrophs acquire carbon?
Amino acids, fatty acids, organic acids, sugars, nitrogenous bases, aromatic compounds
What does chemoautotrophic mean?
Organisms that are able to synthesis they own organic molecules from the fixation of CO2 straight from sources
What does chemoheterotrophic mean?
Organisms that cannot synthesis their own organic materials and therefore need to break down readily synthesised carbon in order to acquire it
Photoautotrophic meaning
Organisms that can synthesise its own food from inorganic material using light as a source of energy
Photoheterotrophic meaning
Organism that uses light for energy but cannot use CO2 as its sole carbon source and therefore uses organic compounds from the environment
What are some of the benefits of viruses?
- Control animal population
- Kill pests
- Oncolytic - destroy cancer cells
What are zoonoses?
Diseases that can cross species boundaries
How are viruses zoonoses?
Vectors
How were viruses discovered?
Through a filtration process that would normally filter out bacteria so it was concluded that they’re smaller than bacteria
Characteristics of viruses?
- Small (20-300nm - too small to be seen with light microscope)
- No metabolism
- Obligate intracellular parasites (need hosts)
- Dormant on surfaces but replicate when they penetrate a host cell using hosts synthesising machinery
- Genetic information usually encoded as one linear OR circular piece of DNA/RNA
- Contain protein coat surrounding nucleic acid
What are some methods used for culturing animal virus?
- Embryonated eggs
- Living animals
- Cell cultures
What is the plaque method?
Sample mixed with phages
Monolayer of cells-detect number of cells destroyed
Viral infection = lysed cells = clearings
Clearings = Plaque
Why don’t antibiotics work against viruses and what is used instead?
Viruses have no metabolism
Instead antiviral medicines are used but they usually interfere with viral multiplication which can interfere with the host cell and be toxic
Attenuated vaccination meaning?
Weakened
Inactivated vaccination meaning?
Dead
Subunit vaccination meaning?
Only antigenic (stimulated immune system)
Conjugate vaccination meaning?
Antigen and protein to aid its recognition
Nucleic acid vaccination meaning?
Injected DNA/mRNA
How do most viruses come to be?
Self-assemble spontaneously
Where is the structural information of a virus stored?
Proteins
What is the capsid?
A protein coat that surrounds the genetic material (genome)
What is a capsomer?
Clusters of proteins that make up the capsid (EM)
What is the envelope of a protein?
Lipid bi-layer surrounding the capsid in some viruses
What are peplomers?
Glycoproteins in the EM
What is multimeric?
Multiple peptide chains
Capsomers and peplomers are both multimeric
What is a complete virus particle called?
Virion
What does the capsid need to be protected from and why?
Nucleic acids are fragile and needed to be protected from:
- UV radiation
- Extreme pH (gastrointestinal tract)
- Dehydration (exposure to air)
- Enzymatic attack (bodily fluids)
Functions of the capsid?
- Packaging nucleic acid
- Host cell recognition
- Genomic material delivering
Structures of capsid
- Linear array of capsid proteins can coil to helix to protect genome
- Triangular unit can form individual faces of a larger structure
What is the most common structure of capsid?
Icosahedral - 20 faces of equilateral triangles
What are the host cells machinery?
Enzymes, ribosomes, tRNA’s
What are the host cells raw materials?
Nucleotides, amino acids and energy
Describe the use of non-structural proteins in viral replication
- Enzymes needed to replicate viral genome
- Needed immediately in small amounts (upon infection)
- Required only inside infected cell
- Will not become part of the virus
Describe the use of structural proteins in viral replication
- Needed to form progeny particles
- Needed in large quantity
- Only needed after genome is replicated
- Needed later to package the genome
e. g. spike proteins, lipid bi-layer
Describe positive sense RNA
Has the same structures of mRNA: methylated cap, start codon, stop codon, open reading frame etc.
Describe negative sense RNA
- Is the complement of mRNA sense
- Has a sequence related to the + by rules of base pairing but is not a reversal of it
- Lacks all recognised features of mRNA
- Cannot be translated - doesn’t make proteins
- Can be copied (transcribed) making a complimentary (positive sense mRNA) strand that might be translated
Which cells do viruses attack?
- Susceptible cell
2. Permissive cell
What is meant by susceptible cell?
Entry allowed by having the right cell attachment factors, receptors or co-receptors
What is meant by permissive cell?
Viral replication is supported, all the right tools and building blocks are there for a given virus
What is the endocytic route of virus attack?
(no membrane) Clathrin mediated endocytosis and penetration
What is the non-endocytic route of virus attack and the 4 steps (HIV as example)?
(present membrane) fusion at cell surface to release capsid into cell
- HIV glycoprotein binds to receptor (CD4)
- HIV glycoprotein binds to co-receptor (CCR5 mainly)
- HIV envelope and plasma membrane fuse together
- HIV capsid released and disassemble in cytoplasm
What is a mesophile?
Organisms that grow best at body temperature (37ºC) - most pathogens thrive at body temperature
Ranges from 10-50ºC
What is a thermophile?
Thrives between 40-70ºC
Above 65ºC, only prokaryotes survive
What is a hyperthermophile?
Thrives between 65-110ºC
Mainly archaea thrive at very high temperatures (no bacteria above 95ºC
What is a psychotroph?
Optimum grown rate at approx 20ºC
Range is 0-30ºC
What is a psychophile?
Optimin growth is approx 10ºC
Range is -10-20ºC
What is an acidophile?
Tolerates low pH
pH 0-6
What is a neutrophile?
pH 5.5-8
What is an alkaliphile?
pH 8-14
What is a halophile?
Organisms that require salt, specifically NaCl
What is an osmophile?
Adapted to environments with high osmotic pressure like high sugar concentrations
What is a xerophile?
Organisms adapted to living in low Aw
What is a hypotonic environment?
Low salt so water moves into the cell - cell may burst
What is an isotonic environment?
No net movement of water
What is an hypertonic environment?
High salt/sugar so water moves out of the cell - cell might shrink
What is a microaerophillic?
Requires oxygen but at lower levels than atmospheric oxygen
What is aerotolerant?
Cannot use oxygen for growth but are unaffected by the presence of it
