Microbial growth and antibiotics Flashcards
What is 4 types of shape in bacteria?
Cocci(こかい) - spherical
Bacilli(バチリ) – rod shape
Spirilla(siフィリア) – spiral shaped
Vibrio(ビブリオ) – curved shape
What is examples of cocci?
Staphylococcus aureus
Diplococcus pneumoniae
Streptococcus pyogenes
S.thermophilus
What is examples of bacilli?
Salmonella typhi
Escherichia coil
Azotobacter
Bacillus anthracis
What is examples of spirilla?
Spirillum rubrum
Treponema pallidum
What is examples of vibrio?
Vibrio cholerae
What is difference between prokaryotes and eukaryotes?
No nucleus vs Nucleus
Circular DNA vs linear DNA
No membrane bound organelles vs Membrane bound organelles
No endoplasmic reticulum vs Endoplasmic reticulum
No golgi body vs Golgi body
No mitochondria vs Mitochondria
No organised chloroplasts vs Chloroplasts in photosynthetic cell
Mesosome vs No mesosome
70s ribosome vs 80s ribosome
1 – 10 nanometer vs 10 – 100 nanometer
What is structure all bacteria have?
Cell wall
70s ribosome
Food reverse granule
Cell surface membrane
Cytoplasm
What structure is sometimes present in bacteria?
Mesosome
Circular DNA
pili
Photosynthetic membranes
Flagellum
Capsule layer
What is cell wall?
Rigid structure for shape
Made of murein(peptidoglycan)
What is gram staining?
Classify bacteria as gram positive or negative
What is gram positive?
A cell wall is gram positive if 40% to 95% is murein
Identified by purple stain on gram staining
What is gram negative?
A cell wall is gram negative contain as little as 5% murein
Don’t retain crystal violet
Stained red if counter stain used
What is mesosome?
Infolding of cell membrane
Contain enzymes involved in respiration
Aid cell division during separation of DNA into new cell
What is circular DNA?
Contain genetic info
Has zone called nuclear zone
What is pili?
Used in reproduction
Similar to flagellum
What is 70s ribosome?
Smaller ribosome
Involved in translation at protein synthesis
What is photosynthetic membranes?
Infold membrane
Contain photosynthetic substance
What is food reserve granule?
Contains food source e.g. polysaccharides
What is flagellum?
Made of flagellin
Gives mobility
What is cell surface membrane?
Made of phospholipid bilayer and protein
Selectively permeable
Controls what in and out
What is capsule?
Mainly polysaccharides and some polypeptide
Protection against phagocytosis and antibiotics
Prevents dehydration
What is plasmid?
Pieces of DNA
Contain few genes
Beneficial effects e.g. antibiotic resistance
What is process of Binary fission?
Cell elongate, DNA replicate then attaches to mesosome
A septum synthesised to divide
Septum grow across dividing the genetic material
Cytokinesis happens
What is called time bacteria population require to double?
Generation time
What is equation for binary fission?
2n
n is generation
2 ways for cell to obtain energy?
Obtain light
Oxidise chemical compound
What is photoautotrophs?
Use co2 in photosynthesis
What is photoheterotrophs?
Use organic source in photosynthesis
What is chemotrophic bacteria?
Obtain energy using chemical compound
They break down compound leading to production of ATP
What is chemoautotrophic bacteria?
Obtain energy by oxidising inorganic compound
What is chemoheterotrophic bacteria?
Obtain energy by oxidising organic compound
Most of bacteria
2 types of bacteria growth method in lab?
Batch culture
Continuous culture
What is growth phases in typical growth curve?
Lag phase
Log/exponential phase
Stationary phase
Death phase
What is lag phase?
No or little cell division
But cell may increase in size
Synthesise RNA, proteins and enzymes
Nutrient specific enzymes might be produced
If bacteria used to environment, it might get shorter
What is log phase?
Cell at maximum division rate
All condition optimal for growth
No limiting factor
Primary metabolite formed and excreted
What is stationary phase?
No increase in population
Limiting factor appeals
Secondary metabolites which is not essential might be produced and excreted
What is death phase?
Unfavourable condition increase so death rate above growth rate
Autolysis may often occur
What effect does temperature have on bacteria growth?
Low temp – slow due to low kinetic energy reducing enzymes activity on metabolism
High temp – most bacteria gets destroyed as enzymes denature
Extremophile may be adapted
What effect does pH have on bacteria growth?
Extremely high or low pH would cause denature of enzymes required for metabolism
What effect does O2 concentration have on bacteria growth?
Depends on microbe type
If obligate aerobes high concentration is ideal
If obligate anaerobes low concentration is ideal
List types and properties of microbes in relation to their O2 preferences?
Obligate aerobes – live only when O2 present
Obligate anaerobes – live only when no O2 present
Facultative anaerobes – can live in both, prefers O2 present
Aerotolerant anaerobes – prefers anaerobic but can live with O2
Microaerophiles – anaerobic condition required but low O2 concentration is fine
Name all types of extremophiles?
Halophiles
Alkalinophiles
Acidophiles
Barophiles(Piezophile)
Thermophiles
Psychrophiles
Halophiles?
Survive in high salt conc
High conc of salt in cytoplasm preventing osmosis out of cells
Optimal folding proteins tolerating high salt conc
Cell wall is composed of glycoprotein and stabilised by sodium ions
Alkalinophiles?
Optimal in pH above 9.0(Alkali)
Membrane and cell wall resist dissolution
Adapted proteins
Intracellural pH close to 9.0
Actively pump hydrogen ions in to use ATP synthase
Acidophiles?
Optimal in below pH 5.0
Acid resistant cell walls and membranes
Activelly pump out excess protons
Barophiles
Preferably or exclusively at high hydrostatic pressure
Barotorelant - high to 500 atmosphere
Barophilic - requires high pressure, usually at 700, 800 atmosphere, not less than 400 atmosphere
Increased pressure decrease binding capacity, so enzymes must be folded in such a way to minimise this
Lipid bilayer is more tightly packed so provide more rigid structure and shields the inside
ompH gene code for a protein at high pressure but inhibited at low, so enables uptake of wider range of nutrients
Thermophiles?
Optimum above 45 celcius
If above 80 celcius is hyperthermophiles
High saturated fatty acid in membrane for stability
More chemical bonds to maintain protein shape
Loops of polypeptide less or absent
Less amino acids unstable at high temp
Chaperones refold denatured proteins
DNA use DNA-binding proteins and reverse DNA gyrase to introduce supercoils into DNA
Psychrophiles?
Optimal at 15 celcius or below
Cold adapted enzymes
Increase in unsaturated fatty acid as temp reduce to control membrane fluidity
Antifreeze protein bind to ice ctrystal preventing piercing of membrane
What is 2 methods used to estimate cell number in microbal population?
Total cell count(death and living cell)
Viable cell count(living cell)
What is haemocytometry and describe?
Total cell count
Use chamber as haemocytometer
Volume is 0.004mm3
Well mixed sample diluted
Then counted, averaged and using dilution factor estimated
What is turbidimetry and describe?
Total cell count
Use colorimeter
Culture medium become more turbid(cloudy) as cell increase
Culture is well mixed before measure
Optical density measured
Cannot differentiate living and death
Dilution plating?
Variable cell counts
Dilution factor calc is done to liquid culture
Done aseptically
Fungi properties?
Eukaryotic
Some can be unicellular
They are heterotrophic(use organic matter)
They can be parasitic, mutualistic or saprophytic
Use extracellular digestion
Filamentous fungi properties?
Fine, branched thread called hyphae
Hyphae forms mass called mycelium
What is structure of fungi?
Cell wall made of chitin
Same as other eukaryotes
Some are coenocytic, so no cross wall between each other
What is name of 2 methods used for measure of fungi growth?
Increase in diameter mycelium - only on filamentous fungi
Increase in dry mass - any microorganism
Describe how to measure increase in diameter of mycelium?
Used in filamentous fungi
If effect of temperature on the growth measured:
Agar plates containing identical concentration of nutrients are
inoculated with the same quantity fungi
Obtain equal sized pieces of mycelium, place in the centre of each plate
Each plate is incubated at a different temperature in the range
All other environmental conditions are standardised e.g. nutrient concentration and pH
The increase in the diameter of the mycelium is measured and recorded daily
These results can be plotted on a graph and the optimum temperature determined
Describe how to measure increase in dry mass?
Used in microorganisms
If the effect of pH on the growth rate of a
filamentous fungus measured:
Set up flasks containing liquid broth media of the same volume and nutrient concentrations
Inoculate each flask aseptically with the same mass of fungal mycelium
Each culture is incubated at a different pH using buffers
Ensure temperature is standardised and at the optimum
At suitable time intervals, remove an identical volume of sample
from each culture and determine the dry mass of fungus in pH culture.
The dry mass is determined by placing the sample in an oven until all the water is removed.
Dry mass at each pH can be plotted on a graph and the optimum pH for the growth of that particular fungus determined.
For oven, heat at 100°C for an hour, remove and weigh it.
Reheat for 15 minutes and reweigh it until you get two constant masses
List source of contamination in experiment?
Non-sterile apparatus
Air
Skin surface
Work surface
List aseptic techniques to prevent contamination?
Use sterile syringes/pipettes/equipment
Flame top of test tube/bottle/inoculating loops
Minimise exposure to the air by lifting lid of dish lightly
Avoiding sterile apparatus touch skin or work surface
How should a culture media be prepared?
Maybe solid or liquid
They must contain balanced mixture of required nutrients
So desired species grow
What is phototrophic bacteria?
Obtain energy via light during photosynthesis
Light utilised by pigment e.g. bacteriochlorophyll
How and why should complete/Complex media be prepared and used?
Used for wide range of microorganism growth or when no exact nutrients are known
It cantains all nutrients required for growth e.g. glucose, amino acids, water, salts, vitamins, trace elements
How and why selective/minimal media?
Suitable for growth of specific microorganism
If inoculated with mixed culture, only species the medium designed for will grow
Growth of others will be supressed
Condition would also be for specific spicies
How can sterilise specific equipment?
Direct heating - Inoculating loop, neck of tubes
Autoclaving - glassware, unwanted culture
Burning alcohol - glass
Disinfectants - inanimate objects
Ultrafiltration
Why do we use streak pleating?
To obtain pure culture from mixed culture of bacteria
Streak plateing method?
Use inoculating loop to move bacteria to agar plate
Lift the lid of petri dish slightly to minimise air exprosure
Streak the agar plate with sample
Reflame loop
Re-streak sample on plate at right angle from last time
Incubate the plate at 25 degrees celcius for 2 days
During exam include asepctic technique and how it prevent contamination of the culture
What is sub-culturing?
Using aseptic technique pick and transfer a sample from a single colony onto another agar plate and incubate
What is bioassay?
Determines the effectiveness of a compound by seeing compound effect on growth of microorganism
Also used to screen microorganism to determine for antibiotic prodcution
This is by measuring their ability to inhibit the growth of bacteria on a bacteria lawn
What is antibiotics?
Compound produced by microorganims inhibiting or killing bacteria
Can work in either in bacteriostatic or bactericidal
In natural enviroment, fungus antibiotic is ecological advantage as reduce competition
How does bacteriostatic work?
Inhibits or prevent bacteria growth
How does bacteriocidal work?
Actually kill the bacteria
Bioassay screening method for specific fungus to specific bacteria?
Take an agar plate seeded with bacteria
Place a mycelial disc from the fungus onto centre of agar
Incubate the plate
If the antibiotic produced by fungus is effective against bacteria then a clear zone will result
Clear zone represents inhibition of growth or death of bacteria
Larger the diameter, the more effective
What is bioassay method for semi-synthetic antibiotics or synthetic antibiotics?
Take an agar plate seeded with the test bacterium
Then place a standard volume of antibiotic into a standard sized well or use standard sized paper discs with
antibiotic
Incubate at 25 degree celcius for 48 hours
A clear zone will be produced if the antibiotic is effective against the bacteria
What is disinfectant?
Chemical compounds that kill bacteria, e.g. Lysol, Dettol
It is possible to determine the effectiveness of a disinfectant by using bioassay
What is antibiotics?
Chemical substances produced by microorganisms or synthetically
It inhibit the growth of or kill other microorganisms
Usually bacteria but few are effective against fungi
They are ineffective against viruses
4 ways antibiotics work?
Inhibiting cell wall synthesis
Cell membrane disruption
Inhibiting mRNA translation
Inhibiting nucleic acid synthesis
What antibiotic inhibits cell wall syntheis and how?
Penicillins and Ampicillin
Inhibits enzymes involved in the syntheis of peptide cross links in the cell wall, causing it to weaken
So burst as osmotic lysis happens
What antibiotic disrupts cell membrane and how?
Polymyxin B
Alters cell membrane structure making it more permeable and leading to cell death
What antibiotic inhibits mRNA translation and how?
Streptomycin and tetracyclines
Inhibit protein syntheis by biding across ribosomes but not on eukaryotic cell
What antibitoc inhibits nucleic acid syntheis and how?
Ciprofloxacin
Inhibits DNA replication
What is broad spectrum antibiotics?
Effective against a wide range of bacteria
May be initially used in the treatment of undetermined bacterial infections e.g. Tetracyclines
What is narrow spectrum antibiotics?
Effective against a small specific group of bacteria e.g. Streptomycin is used to treat infections caused by streptococcus bacteria
Some antibiotics produce allergic effects in certain individuals
Give examples of antibiotic resistance?
Penicillin resistance occurs as bacteria gets genetic mutation to produce enzymes penicillinase and breaks down penicillin
Mutation in change of biding site of antibitic
How can bacteria gain antibiotic resistance?
Spontaneous mutation
Transfer of genes for resistance from other bacteria
What is 2 ways of gene transmission?
Vertical and horizontal
How does vertical gene transmission happens?
Resistance to antibiotics may arise due to a random mutation
Bacteria with resistance gene survive when exposed to the antibiotic
Bacteria reproduce and pass resistance gene on to future generations
Repeated exposure to antibiotics (particularly when dosages of antibiotic are not correctly administered or if the patient does not complete the full course of antibiotic) leads to more bacteria surviving and passing on the gene
Antibiotic resistant bacteria increase in the population lead to an increase in the frequency of the allele for antibiotic resistance
How does horizontal gene transmission happen?
Antibiotic resistance gene are usually on plasmid, and plasmid can contain more than one antibitic resitance gene
The donor cell produces a conjugation tube (pilus) which connects the two bacterial cells
Horizontal gene transmission happens by conjugation
Donor cell replicates its plasmid and passes the copy of the plasmid to the other bacterium
The recipient cell receives the plasmid which may contain a gene for antibiotic resistance
What is transduction
Can pass DNA of one bacteria to other bacteria
Bacteriophage insert its DNA to bacteria
Bacteriophage DNA replicates and host DNA splits into bacteriophage size
New bacteriophages made, some with original bacteriophage DNA some with bacteria DNA
Bacteriophage with bacterial DNA attacks another bacteria
Bacteria gains other bacteria DNA
What is transformation?
DNA drom a lysed bacteria cell is bound to DNA binding protein in the host cell wall
One DNA strands enters host cell as other strand is broken down
The single strand of DNA is bound to the DNA of host cell
Antibiotic resistance of tuberculosis?
Strain of bacterium Mycobacterium tuberculosis has resistance to different antibiotics due to mutation
Icomplete a course of antibiotic treatment enabled to survive and exchange their genes with other bacteria via horizontal gene transmission
So multiple-antibiotic-resistant strains of TB developed
So a cocktail of antibiotics is often used to treat TB
Scientists are trying to develop more effective antibiotics to treat TB and other bacterial infections
Antibiotics resistance of MRSA?
MRSA (methicillin-resistant Staphylococcus aureus) is the name of any strain of the Staphylococcus aureus that is resistant to antibiotics
MRSA is difficult to treat and is prevalent in hospitals as:
Many antibiotics being used - enabling multiple-resistance to develop
Close proximity of patients - ideal for transmission of infections
Weak and sick individuals - more vulnerable to infection by MRSA.
How is C.difficile infection happening?
When antibiotics is used in patients it decrease competition in body and increase and release toxin(Opportunistic bacteria)
What is sympthoms of C.difficile infection?
Mild to severe diarrhea
Severe inflammation of the bowel
Who is at risk in C.difficile infection?
People treated with broad spectrum antibiotics
People with serious underlying illnesses
Elderly
How is C.difficile spread?
Hands of healthcare and other people in contact with patients or their enviromental surfaces contaminated with bacteria or spores
Spores are produced when bacteria encountered with unfavolable condition
They survive on clothes and surfaces for long period even when cleaned with alcohol
What is treatment of C.difficile?
the use of specific antibiotics which will kill C. difficile (e.g. either metronidazole or vancomycin)
Probiotic supplements which are designed to stimulate the growth of ‘good’ bacteria (although the evidence of their effectiveness in treating CDIs is inconclusive)
Injections of immunoglobulins to enhance the production of antibodies available to fight off the infection
Fecal transplantation – this treatment involves transplantation of a fecal sample from a healthy donor
Serious infection may require surgery to remove a damaged section of the bowel.
