explain why knowing about microbial nutrition is important
- helps us grow and identify microorganisms by providing the right nutrients and conditions in lab cultures.
- allows us to understand and control pathogens, since their nutrient needs affect infection and treatment strategies.
- important for industrial and environmental applications, like fermentation, antibiotic production, and bioremediation.
define the different methods that are used to grow organisms
-culture media
-> liquid (broth) vs solid (agar)
-> complex (yeast) vs defined (put in each chemical individually)
-> selective (favor the growth of certain organism) vs differential (allows multiple organisms to grow)
- axenic (contains only single species) vs enrichment culture (favors the growth of a specific type of organism from a mixed population)
- batch (fixed volume of nutrient medium) vs continuous (fresh medium continuously added0
what is great plate count anomaly
- more cells visible in direct microscopy count than plate count
- 0.1-1% will grow on petri dish
- many dead cells
- VBNC = viable but not culturable - some may be dormant state but many may just not have the appropriate conditions to elicit growth
- lots of bacteria cant grow on the media -> wrong substrate, wrong concentration, wrong conditions (T, pH, etc)
- some cells grow too slowly to observe or are overrun by fast growing organisms
what are the environmental factors that affect microbial growth
- many microbes have evolved the ability to survive in environments that we consider to be extreme
-> extremophile
-> thermophile = areas of high temp
-> halophile = high salt concentrations
-> psychrotolerant = low temps - tolerant = conditions that allow survival
- obligate = condition required for growth
- facultative = organism can grow under a condition but the condition is not required
- water activity, temp. pH, oxygen conc, pressure, radiation
how many microbes are out there
- estimated 1 trillion species of bacteria and archaea
- cultivated 18.9% of bacteria and 6.8% of archaea
why do we grow microbes
- isolating new microbes is a major goal in microbiology
- to understand them better
- learn about their physiology and metabolism to understand their role in the environment
- sequence and analyze their genomes to study their evolution and the functions encoded in their genomes
- understand special things that they are able to do
- expand the known realm of microbes
what are the 4 classes of biochemical needed for microbes to grow
- nucleic acids
- proteins
- carbohydrates
- lipids
nutrient requirements for macronutrients and micronutrients
macronutrients - nutrients required in relatively large amounts
-> g/L : C, N, O
-> mg/L : P, H, S, Fe, Ca, K, Na+
micronutrients - nutrients required in trace amounts
-> ug/L : Cu, Zn, Se, Mn, Co, tungsten
what are nutrient requirements
- growth factors -> organic compounds the cell cant make such as (vitamins, amino acids, purines, pyrimidines, heme, and cholesterol)
- specific elements may be required by specific organisms
-> oxygenase enzymes have high Cu requirements
-> NOB require Mo for the enzyme nitrite oxidoreductase
-> methanogens require W and Se
what are auxotrophs
- nutritional mutant that has lost the ability to synthesize certain nutrients
what is the metabolic diversity for humans and E.coli, P. aeruginosa
energy source = chemicals (chemo)
electron source = organic (organo)
carbon source = organic (hetero)
chemoorganoheterotroph
what is the metabolic diversity of plants, blue green algae- prochlorococcus
energy source = light (photo)
electron source = inorganic (litho)
carbon source = inorganic/C1 (auto)
photolithoautotrophs
explain some details about metabolic diversity
- autotrophy (C fixation) is much more widespread in microbial world
- anaerobic respiration and fermentation (anoxic conditions)
- chemolithotrophy is common
-> nitrifying bacteria in wastewater treatment (nitrosomonas)
what are some traditional microbiological methods
- plate environmental sample on defined media
- count colonies to estimate the number of organisms in an environment
- isolate individual organisms
- examine the physiology and metabolism of organism in pure cultures
what are some nutrient preferences (oligotroph and copiotroph)
oligotroph = organisms that prefer to grow at very low nutrient concentrations, may be inhibited at higher concentrations
copiotroph = organisms that grow in environments rich in nutrients (E.coli, high conc of glc)
- oxygen preference
-> aerobes vs anaerobes
-> microaerotolerant aerobes
-> aerotolerant vs obligate anaerobes
what is osmosis
- movement of water across a semipermeable membrane from a region of low solute concentration to a region of high solute concentration
- dissolved molecules are called solutes
- most solutes cannot cross membranes
- as solute concentration increase , free water concentration decreases
- hypertonic = high [solute]
- hypotonic = low [solute]
what is osmotic pressure
- water availability depends on both the wetness of an environment and the solute concentration
- under normal conditions, cells have a positive water balance (water diffuses into the cell)
- if the exterior solute concentration is higher then water flows out of the cell resulting in dessication
water activity : Aw (between 0 and 1; water =1)
Aw = vapor pressure of air in eq with a substance or solution/ vapor pressure of pure water
halophile, osmophile, xerophile all grow best under low water activity so whats the difference
halophile = (haloferax volcanii) high salt concentration
osmophile = (wallemia sebi) high organic solute concentration
xerophile = (rhizopus stolonifera) dry environments
define halophile, halotolerant, osmophile, xerophile, osmotolerant
halophile = microorganism that requires high levels of sodium chloride for growth - ionic
halotolerant = ability to withstand large changes in salt concentration
osmophile = microorganisms that grow best under low water activity conditions and may not be able to grow at high Aw levels - high solute
xerophile = microorganisms that grow best in or on media with low water availability - dry enviroment
osmotolerant = organism that grow or survive over a fairly wide range of water activity or solute concentration
cells need to be hypertonic to their environment, how do they survive in low Aw
- decrease their own Aw
- increase internal solute concentration
-> pumping inorganic ions into the cell from the environment - KCl
-> synthesizing or concentrating an organic solute - compatible solutes
-> noninhibitory to biochemical processes within the cell ex. glycerol
what are cardinal temperatures
- the minimum, optimal, and maximum temperature at which an organism grows
define psychrophile, psychrotolerant, mesophile, thermophile, hyperthermophile
psychrophile = grows best at cold temps
psychrotolerant = can grow at low temps, but optimal around 20 deg
mesophile = grows best at moderate temps
thermophile = prefers high temps
hyperthermophile = extremely high temps
why do max. min. and optimum temps exist
- enzyme and protein structure
-> at high temp, enzymes denature (unfold)
-> at low temp, enzymes have low flexibility, cannot catalyze reactions properly - cytoplasmic membrane
-> must be in a semi-fluid state for transport processes to function properly - temperature optima reflect maximal functioning of cellular components
describe what happens at each stage of temp
minimum = membrane gelling, transport processes are too slow for growth to occur -> not flexible enough
optimum = enzymatic reactions occur at maximal rate
maximum = proteins denature, cytoplasmic membrane collapses -> too flexible
