Biol 3508
Microbial Physiology and Biotechnology
Lecture 10 -11
Microbial Nutrition and
Means of Nutrients uptake
Microbial Nutrition
Outline
I. Nutritional Requirements of Microorganisms
II. Means of Nutrients Uptake by Microbial Cells
III. Application of Microbial nutritional requirements:
cultivation of microorganisms
Learning Outcome
Know nutrient requirements of microorganisms
Understand the various processes and mechanisms by
which microorganisms obtain nutrients from the environment
Describe the various types of culture media for
microorganisms, techniques used to obtain pure cultures,
and their applications in the study of microorganisms
Elements of life
All living organisms must have the sources of :
Nutrients: a supply of elements that are used to construct the
molecules of life
Energy: capacity to do work or to cause particular changes
• Macronutrients (macroelements)
– C, O, H, N, S, P, K, Ca, Mg, and Fe
C, O, H is often
acquired simultaneously
Electrons (required for
oxidoreduction reactions):
• Micronutrients (trace elements)
– Mn, Zn, Co, Mo, Ni, and Cu
Nutritional Types Classification of Organisms
Based on Their Acquirement of Carbon,
Energy, and Electrons
• Based on carbon source
– Autotrophs: CO2
– Heterotrops: Reduced, preformed organic molecules
• Based on energy source
– Phototrophs: Light
– Chemotrophs: Oxidation of chemical compounds
• Based on electron source
– Lithotrophs: Reduced inorganic substances
– Organotrophs: Reduced organic substances
Nutritional Types Classification of Organisms
Based on Their Acquirement of Carbon,
Energy, and Electrons
Energy
Nutritional Types of Microorganisms
Photolithoautotrophs Chemoorganoheterotrophs
Nutritional Types of Microorganisms
Cyanobacteria (a Pollute Purple non-sulfur bacteria
photolithoautotroph) degradation (photoorganoheterotrophs)
Nitrobacter winogradskyi (a Chemical transformation Beggiatoa alba (a
chemolithoautotroph) of reduced N, S to chemolithoheterotroph)
nitrate, sulfate etc.
Requirements for Nitrogen, Phosphorus, and Sulfur
– Nitrogen:
Direct:
• Organic molecules, i.e. amino acids NADPH + H+
NH3 +
• Ammonia
Indirect:
• Nitrate via assimilatory nitrate reduction
Assimilation: the conversion of
nutrient into the fluid or solid
substance of the body, by the
processes of digestion and absorption
• Nitrate reduction to nitrite
catalyzed by nitrate reductase
• Reduction of nitrite to ammonia
catalyzed by nitrite reductase
• Nitrogen gas (N2) via nitrogen fixation
Reduction of atmospheric nitrogen to ammonia
Catalyzed by nitrogenase
- Unreactive gas: fixation requires large
ATP expenditure
Nitrogenase
N2 + 16ATP + 8e- + 8H+ 2NH3 + 16ADP + H2 + 16Pi
- Expression of the relevant genes and activity of the
enzymes are under tight control
Ø Lacking of fixed-nitrogen sources
Ø Lacking of O2
Ø Temperatures at or below 30 °C
- Found only in a few species of prokaryotes
https://www.jove.com/embed/player?id=12119&access=c99054fe0b&t=1&s=1&fpv=1
Requirements for Nitrogen, Phosphorus, and Sulfur
– Phosphorus:
l Inorganic P, can be directly incorporated into cell components
– Sulfur:
l Reduced form such as Cysteine
l Sulfate and reduce it by assimilatory sulfate reduction
O-acetylserine
activated
sulfate (PAPS)
Growth Factors
• Organic compounds
• Essential cell components (or their precursors) that the
cell cannot synthesize
• Must be supplied from environment if the cell is to
survive and reproduce
Classes of Growth Factors:
• Amino acids
– protein synthesis
• Purines and pyrimidines
– nucleic acid synthesis
• Vitamins
– enzyme cofactors
Uptake of Nutrients by the Cell
• Some nutrients enter by passive diffusion:
- A process by which molecules move from a region of higher
concentration to one of the lower concentration
- Small, non-poloar molecules such as O2 and CO2
• Most nutrients enter by:
– Facilitated diffusion
Diffusions involving channels or carrier proteins
– Active transport
Transport of solute molecules against a
concentration gradient with the input
of metabolic energy
– Group translocation
Chemically modifies molecule as it is brought into the cell
https://www.jove.com/embed/player?id=10700&access=578b037583&t=1&s=1&fpv=1
Facilitated Diffusion
- Diffusions involving carrier proteins
Q: are there any prokaryotic
• Similar to passive diffusion: cellular structures that can help
– Is not energy dependent to maintain a relatively large
– From high to low concentration concentration gradient for solute
and aid the facilitated diffusion
• Differs from passive diffusion: process in the cell?
– Uses carrier proteins (permeases)
– Rate increases more rapidly than passive diffusion at lower concentration
– Transport closely related solutes
– Effectively transports glycerol, sugars, and amino acids
a b
https://www.jove.com/embed/player?id=11875&access=48ffa89aa3&t=1&s=1&fpv=1
Active Transport
The transport of solute molecules to higher concentrations, or
against a concentration gradient, with the input of metabolic energy
• Energy-dependent process
– ATP or proton motive force
• Against the concentration gradient
• Involves carrier proteins (permeases)
– carrier saturation effect is observed at high solute concentrations
Two types depending on energy sources:
I. ABC (ATP-binding cassette)Transporters:
primary active transport
Example:
maltose binding
protein in E. coli
II. Active transport using proton
and sodium gradients
(Secondary active transport)
Energy source: proton motive force (PMF)
Symport
- Linked transport of two substances in the
same direction
ETC or proton pump
Antiport
- Linked transport in which two
substances move in opposite directions
https://www.jove.com/embed/player?id=11880&access=f0bb48462d&t=1&s=1&fpv=1
Group Translocation
- The process in which the molecule is chemically
modified as it is brought into the cell
• Energy-dependent
• Best known system is the
phosphoenolpyruvate: sugar
phosphotransferase system (PTS)
• PTSs widely distributed in bacteria
Glucose, fructose,
mannitol, sucrose, N-
acetylglucosamine etc.
PEP: phosphoenolpyruvate
A microorganism often has more than
one transport system for a nutrient,
they differ in:
• Energy source 2nd role of PTS: a receptor of
• Affinity for the solute transported chemical attractants
• Nature of their regulation
Iron Uptake
• Uptake is difficult
• Microorganisms use
siderophores to aid uptake
• Siderophores: low molecular
weight organic molecules that E. coli
bind ferric iron and supply it to Fungi
the cell The condition in cytoplasm is
more reduced than periplasm
In E. coli:
Siderophore receptor in OM
ABC transporter transfer through the IM
Reduced to ferrous ion
Culture Media
• A solid or liquid preparation used to grow, transport, and store
microorganisms.
• Most contain all the nutrients required by the organism for growth
Types of Media:
Some Media Components:
• Peptones: protein hydrolysates from partial digestion of various protein
sources
• Extracts: aqueous extracts, usually of beef or yeast
• Agar: sulfated polysaccharide used to solidify liquid media
Defined or Synthetic Media: Complex Media:
all components and their contain some ingredients of unknown
concentrations are known composition and/or concentration
Macronutrients: C, O, H, N, S, P, K, Ca, Mg, and Fe
Functional Types of Media
• Supportive or general purpose media
– Support the growth of many microorganisms
– e.g., tryptic soy agar
• Enriched media
– General purpose media supplemented with blood or other
special nutrients
– e.g., blood agar
• Selective media
– Favor the growth of some microorganisms and inhibit growth
of others
– e.g., MacConkey agar, Eosin-methylene blue (EMB) agar
• Differential media
– Distinguish between different groups of microorganisms based on
their biological characteristics
– e.g., blood agar, MacConkey agar
E. coli on blood plate
E. coli on Eosin methylene E. coli on MacConkey's agar
Supportive blue (EMB) agar
Selective Selective
Lactose and non-lactose
Haemophilus influenzae fermenting gram negative bacilli
on blood agar Blood agar culture of bacteria
from the human throat on MacConkey plate
Differential, or both
Supportive Enriched and differential
Selective and differential
Isolation of Pure Cultures
• Pure culture
– population of cells arising from a single cell
– Isolation of pure culture is very important for
microbiological studies
• Techniques used to isolate pure cultures:
Spread plate, Streak plate, and Pour plate
• Colony: visible growth or cluster of microorganisms in or on
solid medium. Each colony represents a pure culture.
Streak Plate Technique:
Spread Plate Pour Plate
1. dispense cells (30-300)
onto medium in petri dish
2. - 3. sterilize spreader
4. spread cells
across surface
