Chapter 7:
Microbial Nutrition, Ecology, and Growth
Nutrition - process by which chemical substances (nutrients) are
acquired from the environment and used in cellular activities
Essential nutrients - must be provided to an organism
Two categories of essential nutrients: Macronutrients and
Micronutrients
Macronutrients - required in large quantities; play principal roles in
cell structure and metabolism. Proteins, carbohydrates.
Micronutrients/Trace elements - required in small amounts;
involved in enzyme function and maintenance of protein structure.
Manganese, zinc, nickel
Organic nutrients - contain AT LEAST carbon and hydrogen and
are usually the products of living things. Methane (CH4),
carbohydrates, lipids, proteins, and nucleic acids.
Inorganic nutrients - an atom or molecule that contains a
combination of atoms other than carbon and hydrogen. Metals and
their salts (magnesium sulfate, ferric nitrate, sodium phosphate),
gases (oxygen, carbon dioxide) and water.
Escherichia coli components - 70% water. 96% of cells are composed
of 6 elements: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus,
and Sulfur.
E.coli minimal media needs - (NH4)2SO4, FeCl, NaCl, Trace elements, Glucose
(C6H12O6), KH2PO4, MgSO4, CaHPO4, H2O
What determines the nutritional category of a species? - their energy
and source of carbon
Differences in ENERGY include - Chemotrophs and Phototophs
Chemotroph - gain energy from chemical compounds
Phototroph - gain energy through photosynthesis
Differences in obtaining carbon include - Heterotrophs and
Autotrophs
Heterotroph - must obtain carbon in an organic form made by other
living organisms such as proteins, carbohydrates, lipids, and nucleic
acids
Autotroph - an organism that uses CO2, an inorganic gas as its
carbon source and is Not nutritionally dependent on other living
things.
Most organisms also require some other organic molecules that they
can’t synthesize - Organic compounds that cannot be synthesized by
an organism because they lack the genetic and metabolic mechanisms
to synthesize them. Growth factors must be provided as a nutrient.
Growth factors - Essential amino acids, vitamins, NADH, some basic
building blocks. Often specific to a given organism.
Nutritional categories include - photoautotrophs, chemoautotrophs,
and chemoheterotrophs.
Two types of Photoautotrophs - oxygenic and anoxygenic
Oxygenic Photoautotrophs - Oxygenic photosynthesis (sunlight
absorbed by chlorophyll) CO2 + H2O to (CH2)n + O2), Use light for
energy (photo) and CO2 for carbon source (auto), Produce oxygen
(oxy)
Examples of Oxygenic Photoautotrophs - Photosynthetic bacteria
(cyanobacteria), Algae, and Green plants
Anoxygenic Photoautotrophs - anoxygenic photosynthesis (sunlight
absorbed by bacteriochlorophyll)
CO2 + H2S to (CH2O)n + S + H2O, Cannot use water as a source of
electrons to make reducing power– instead use H2S, are Anaerobic
and Oxygen is toxic, Found in bogs and mud , Use
bacteriochlorophylls (for light that penetrates to greater depths).
Example of Anoxygenic Photoautotrophs - Green & Purple Sulfur
Bacteria which oxidizes sulfide/sulfur to sulfate or converts
Hydrogen gas to water.
Chemoautotrophs/lithoautotrophs- survive entirely on inorganic
substances. For example, Methanogens produce methane gas under
anaerobic conditions 4H2 + CO2 CH4 + 2H2O. Where CO2 is the
electron acceptor.
Examples of electron acceptors in chemoautotrophs - CO2:
Methanogens, H2S :Beggiatoa, S: Thiobacillus thiooxidans, NH3 :
Nitrosomonas, NO2- : Nitrobacter, and Fe2+ : Thiobacillus
ferrooxidans.
Majority of organisms are chemoheterotrophs - Use organic
chemical substances as sources of energy and organic compounds
as the main source of carbon. Chemoheterotrophs may
participate in Aerobic or Anaerobic Respiration and its
categories include Saprobes and Parasites.
(Chemoheterotroph) Aerobic respiration - C6H12O6 + 6 O2 to 6 CO2
+ 6 H2O + ATP. Here, Oxygen is the electron acceptor.
(Chemoheterotroph) Anaerobic respiration- use something other than
oxygen as an electron acceptor. Includes: Nitrate (NO3-) to nitrite
(NO2-) to NO to N2O to N2 (denitrification). Inorganic nitrogen is
one of the most common terminal electron acceptors in anaerobic
respiration. Anaerobic respiration is less efficient than aerobic.
Two categories of Chemoheterotrophs - Saprobes and Parasites
Saprobes - free living microorganisms that feed on organic detritus
from dead organisms. Include Opportunistic pathogens and
Facultative parasite
Parasites - derive nutrients from the host. Includes: Pathogens and
Some are obligate parasites
Transport - Getting the Needed materials IN and other materials OUT
Passive transport - does not require energy; substances exist in a
gradient and move from areas of higher concentration toward areas
of lower concentration. Includes: Diffusion, Osmosis, and
Facilitated diffusion
Osmosis - Specialized Passive Transport involving diffusion of
water. Water is the universal solvent allowing organisms can get
dissolved nutrients. Polar water typically diffuses through aquaporins
allowing it to move quickly across the membrane.
Facilitated diffusion - passive transport that requires a carrier. Ex:
Glucose
Active transport - requires energy and carrier proteins; gradient
independent. Includes: Active transport, Group translocation, and
Bulk transport.
Group translocation - transported molecule chemically altered
Bulk transport – endocytosis, exocytosis, pinocytosis
Isotonic solution - water concentration is equal inside and outside the
cell, the rates of diffusion are equal in both directions.
