Bacteria Flashcards
Describe the differences between eukaryotic and prokaryotic cells
what is the microbiome
The microbiome is the genetic material of all the microbes -bacteria, fungi, protozoa and viruses - that live on and inside the human body
List the major types of micro-organism which cause human infectious diseases
viruses
prokaryotes
eukaryotes
what are prokaryotes
Simple, unicellular organisms lacking a defined nucleus, mitochondria or other membrane-bound organelles
protect skin/epithelial tissue from invasion
help food digestion Biotechnology industry
bacteria
archaea
what are the subdivisions of eukaryotes
**eukaryotes**
fungi
protists
- protozoa
- A huge family of single-celled eukaryotic parasites
- Major tropical and zoonotic diseases
How are bacteria named
Shape
Round - ‘coccus / cocci’
e.g Streptococcus sp, Enterococcus sp
Long – ‘bacillius / bacilli’
E.g. Enterobacter sp.
A few are spiral / branched (filamentous), comma shaped
what is gram staining
Ability to take up stain based on the thickness and accessibility of cell wall peptidoglycans
- gram-positive bacteria have a cell wall mainly consisting off peptidoglycan
- gram-negative bacteria have a very thin peptidoglycan layer and an outer membrane
how do you gram stain
Dry on glass plate
Stain with ‘crystal violet’ and set with iodine
Decolourise with alcohol/ acetone
Counterstain with safranin (pink colour)
what are examples of gram positive and negative bacteria
why do mycobacteria have different gram stains?
Basically a Gram positive cell wall
Don’t stain Gram positive
Very thick lipid membrane (mycolic acid mycomembrane) anchored to peptidoglycan layer
Intracellular survival
what is an o antigen
repeating glycan polymer (varies based on strain). Immunogenic.
what is lipid A
anchor for Lipopolysaccharide. Immunogenic
features of a bacterial capsule
- Polysaccharide coat
- ‘hides’ immunogenic cell wall
- Immunity requires antibodies to the capsule
- Metabolic burden on the bacterium
- Confers virulence e.g.
- Haemophilus influenzae
explain the mobile genetic element- ribosome
Engines of protein synthesis
70S (sedimentation rate)
Smaller than in eukaryotes (80S)
Subunits 50S and 30S
Each contains RNA and proteins
Bacterial RNA
Target of antibiotics
Diagnostic tests
explain the mobile genetic element- plasmid
Circular ‘extra-chromosomal’ DNA
Independently replicating
Passed down to progeny
explain the mobile genetic element- transposons
DNA sequences that are able to move location in the genome.
Encode transposase
Plus other genes
Mobile between
genomic and plasmid DNA
gene regulation in bacteria
Bacteria sense and adjust to their environment
Altered growth rate
Regulation of metabolic pathways
Regulate virulence factors
Adhesion molecules
Enzymes to degrade host proteins
Degrade immune mediators
Lyse host cells
Exponential phase ≈ superficial infection / bacteraemia
Stationary phase ≈ abscess
how do bacteria grow?
Bacteria may grow in clusters or chains
Especially important for Gram positive cocci
bacterial growth patterns
Microscopic view:
Form chains / clusters
On solid culture medium:
Form colonies – different sizes / shapes
Excrete enzymes, waste products etc into environment
requirements for bacterial growth
Atmosphere
Nutrients
what are features of aerobes
Use O2 as final electron acceptor (very efficient)
E.g., oxidation of glucose to CO2 and H2O
Some are anaerobes (obligate anaerobes)
Fermentation - final electron acceptor is organic molecule
E.g., glucose to lactic acid
ok when substrates are plentiful
Oxygen is usually toxic to anaerobic bacteria
Some are facultative anaerobes
Can switch between aerobic and anaerobic metabolism
what molecules do bacteria have to import
Purines and pyrimidines
Amino acids
Vitamins
Escherichia coli (E.coli)
Needs glucose and inorganic salts only
Very easy to grow in the laboratory
Treponema pallidum (cause of syphilis)
Specialised enriched medium
Difficult to grow
what is the lag phase
No increase in cell numbers
Adjustment to new environment
Gene regulation
what is the stationary phase
Nutrients become depleted
Metabolites build up
Division stops
Gene regulation
what is the rate of exponential growth
The rate of exponentialgrowthof abacterial cultureis expressed as generation time, also the doubling time of thebacterialpopulation. Generation time (G) is defined as the time (t) per generation (n = number of generations).
what is the exponential phase
Cell doubling
Slope of the curve = growth rate of the organism in that environment
what is the death phase
Exhaustion of resources
Toxicity of environment
what are the rod-shaped bacteria called
bacillus
what are the 3 types of bacillus
what is a spherial shaped bacteria called
coccus
what is a curved shaped bacteria called
vibrio
what is a oblong shaped bacteria called
coccobaccilus
what is a losely coiled bacteria called
spirillum
what is a tightly coiled bacteria called
spirochette
what are the 6 different types of cocci bacteria
what are the growth requirements of bacteria in a lab
Gram staining for bacteria
Samples from sterile site
A single pathogen expected
what is chemotherapy
use of synthetic chemicals capable of destroying infectious agents
