Week 1, Intro to microbes and their growth requirements Flashcards
List some types of microorganisms
> Bacteria > Fungi > Protozoa > Algae > Viruses > Viroids > Prions
Provide the classification, based on atmospheric (oxygen) requirements), the organism in test tube (a)
Obligate aerobe
What units are commonly used to measure microbes?
> Micrometer (µm) = 0.001 mm = 10⁻⁶ m > Nanometer (nm) = 0.001 µm = 10⁻⁶ mm = 10⁻⁹ m
How do most fungi reproduce?
Spores, hyphae.
Explain how microbes are grouped by their energy, electron, and carbon sources.
ENERGY SOURCE - Light (Phototrophs) - Organic or inorganic compounds (by oxidation) (Chemotrophs) ELECTRON SOURCE - Organic molecules (Organotrophs) - Reduced inorganic molecules (Lithotrophs) CARBON SOURCE - CO2 (Autotrophs) - Organic molecules (reduced, preformed, from other organisms, etc) (Heterotrophs)
What does the term ‘resolution’ refer to?
The ability to distinguish two objects as distinct and separate Human eye: 100-200 µm Light microscope: ~200 nm Electron microscope: ~0.5 nm
Explain the method for sub-culturing filamentous fungi
- Label the under-side rim of a fresh potato dextrose agar (PDA) plate 2. Dip the inoculating needle or scalpel into alcohol, flame, cool. 3. Cut a small block (approx 5mm x 5mm) from the actively-growing edge of the mycellium 4. Transfer to the center of the PDA plate 5. Incubate right way up for 1 week at 25 °C
Provide the classification, based on atmospheric (oxygen) requirements), the organism in test tube (b)
Obligate anaerobe
What are some of the roles of microorganisms?
> Nutrient cycling > Waste treatment > Disease and biological control agents > Food and beverage industry (fermentation) > Pharmaceutical industry (antibiotics) > Oil and petrochemical industry (ethanol) > Biotechnology > Understanding basic biology
T/F: Sterilisation degrades vitamins
True
Desribe what a Photolithoautotroph is and give an example of one.
Cyanobacteria is an organism that uses light as its energy source, reduced inorganic molecules for its electron source, and CO2 as its carbon source.
When using asceptic technique, the goal is to kill the most resistant microbial component, which is…?
Bacterial endospores.
What are four sterilisation techniques?
HEAT - Dry heat → denatures microbial proteins → metal utensils: flamed to red-hot → glassware: heat to 160-170 °C in oven → less effective than moist heat - Moist heat → e.g. autoclave (steam under pressure) → 121 °C at 15 psi for 15-20 minutes → glassware, aqeous solutions, disposal of unwanted cultures CHEMICALS - Gases → e.g. ethylene oxide (penetrating, kills all microbes) - Alcohols, e.g. ethanol - Phenolics, e.g. triclosan (hand sanitisers) - Halogens, e.g. bleach, iodine - Heavy metals, e.g. silver - Essential oils, e.g. tea tree oil RADIATION - Ionising radiation → gamma rays, electron beams → lethal, good penetration - UV light → surfaces only (doesn’t penetrate surfaces) * Approved by the FDA and WHO for use on meat, fresh fruit and vegetables, and spices. FILTRATION - for heat-labile liquids (damaged by heat) - for air (HEPA filter, laminar flow hood)
List 3 defining features of microorganisms
- < 1 mm diameter 2. They have a common method of study (microscopy) across different groups of microbes 3. Simple organisation (single cells or cell clusters, or sub-cellular)
Provide the classification, based on atmospheric (oxygen) requirements), the organism in test tube (e)
Aerotolerant anaerobes
(anaerobic regardless of [O₂], e.g. LAB)
T/F: Sterilisation degrades antibiotics
True (denatures)
What is meant by a ‘selective medium’?
A culture medium designed to promote (and/or inhibit) certain species of microbes; e.g. using antibacterial antibiotics to select for fungi.
List some factors that affect microbial growth
- Temperature - pH - Osmotic pressure - Atmosphere
T/F: Sterilisation degrades degrade agar.
False
Explain the (streak plate) method for establishing pure bacterial cultures.
- Label the under-side of the petri dishes and mark the location of the first streak 2. Flame and cool a loop 3. Collect a loop-full of bacterial culture 4. Gently wipe the loop over one side of the agar 5. Flame and cool loop 6. Turn dish anti-clockwise and make 4-5 gentle parallel strokes in one direction through the previous set of strokes 7. Flame and cool loop 8. Repeat steps 6 & 7 twice (or once, then stroke in a zig-zag pattern towards the center) 9. Incubate inverted for 1 week at 25 °C 10. Select an individual colony from the incubated culture and streak on a new agar plate. Repeat as many times as necessary.
What temperature does agar melt and solidify at?
Melts at 100 °C, sets at 42 - 44 °C.
Describe a typical growth curve for single-celled microbes.
Log # of viable cells OVER time 1. LAG PHASE: adjusting to new conditions, synthesising new materials; variable duration 2. LOG (EXPONENTIAL) PHASE: number of cells doubles at a constant rate (1 -> 2 -> 2ⁿ); after n generations, population, N=N₀2ⁿ; population most uniform (chemical and physiological). 3. STATIONARY PHASE: nutrient limitation, accumulation of toxic waste, 2° metabolites (could be lactic acid which changes the pH o the point that it becomes unfavourable, antibiotics produced) 4. DEATH PHASE:
Explain what the term ‘viability’ refers to.
The ability of bacteria and viruses to reproduce, and the ability of filamentous fungi and algae to grow
Explain the process for preparing agar plates for culture.
- Spray and wipe down the work surface with bench cleaner 2. Label the petri dishes on their under-side, around the rim, and place them on the bench with the lids on top and writing underneath (i.e. the right way up) 3. Working quickly, dry the vessel containing the molten agar, remove the cap, flame the opening, raise the lid of the petri dish slightly, and pour in the agar. 4. Rotate the dish gently to evenly distribute the agar. 5. Leave the agar to set.
Define sterilisation
Free from all living organisms
Describe the difference between an obligate aerobe, a facultative aerobe, and a microaerophile.
OBLIGATE aerobes REQUIRE oxygen to survive. FACULTATIVE aerobes prefer (and grow better) in oxygen-rich environments, but can survive in low-oxygen environments. MICROAEROPHILES typically grow in environments with between 2-10% O2.
What is the optimum pH for culturing bacteria?
pH 6-8 Nutrient agar is pH 6.8
What is the optimum pH for culturing fungi?
~ pH 5 PDA is pH 5.6 Acidified PDA is 4.8; used for inhibiting bacteria
T/F: Nematodes aren’t considered microbes.
True. All to do with organisation - nematodes have more complicated digestion, for example)
Define microbiology
The study of organisms too small to be seen by the naked eye
What is meant by a ‘differential medium’?
A culture medium designed to allow for easy identification of certain microbes based on their appearance; e.g. by containing dyes that cause the organism of interest to appear a particular colour.
Explain what ‘death’ means in terms of microbes
The irreversible of the ability to reproduce or grow
Explain the method for sub-culturing bacteria.
Basically just transfer bacterial culture from one tube/dish to another using aseptic technique.
Define ‘sterile’.
Free from all living organisms
How does studying microbes help with our understanding of basic biology?
> Easy to work with > Don’t require ethics approval > Microbes make up a large proportion of our own systems
Explain the method for calibrating an ocular micrometer.
- Place ocular micrometer in one of the eyepieces. 2. Place a stage micrometer on the microscope stage 3. Using the 10x objective, move the stage so that the ocular and stage scales are superimposed at the first increment. 4. Count the number of increments until the lines superimpose over each other again. 5. 1 ocular micrometer = (# ocular micrometer increments) / (# stage micrometer increments) * the distance between the smallest increments on the stage micrometer (µm) e.g: At 10x, 1 ocular unit = 99/100*10 = 9.9 µm At 40x, 1 ocular unit = 15/60*10 = 2.5 µm
Provide the classification, based on atmospheric (oxygen) requirements), the organism in test tube (d)
Microaerophile
Provide the classification, based on atmospheric (oxygen) requirements), the organism in test tube (c)
Facultative aerobe/anaerobe
What is the main difference between nutrient agar (NA) and potato dextrose agar (PDA)?
pH. → NA: 6.8 → PDA: 5.6
How are microbes measured?
> Total cell count > Viable count > Cell mass (turbity, cell volume, dry weight, chemical measurements)
Describe what a Chemolithoautotroph is and give an example of one.
An organism that oxidises organic or inorganic compounds for its energy source, reduced inorganic molecules for its electron source, and CO2 for its carbon source; e.g. Nitrifying bacteria; methanogens; and S, H, and FE oxidisers
How do most bacteria reproduce?
Binary fission or budding
Explain what a ‘culture’ or microbes refers to.
A population of microbes grown outside of their natural environment (e.g. in a lab).
Describe what a Chemoorganoheterotroph is and give an example of one.
An organism that oxidises organic or inorganic compounds for its energy source, organic molecules for their electron source, and organic molecules produced by other organisms for its carbon source; which includes most fungi, pathogens, protists, and archaea
