ERT107
Microbiology for Bioprocess
Engineering
MICROBIAL NUTRITION
Element of life

macroelements (macronutrients)
◦ C, O, H, N, S, P
 found in organic molecules such as
proteins, lipids, carbohydrates, and
nucleic acids
◦ K, Ca, Mg, and Fe
 cations and serve in variety of roles
including enzymes, biosynthesis
◦ required in relatively large amounts

micronutrients (trace elements)
◦ Mn, Zn, Co, Mo, Ni, and Cu
◦ required in trace amounts
◦ Part of certain enzyme
◦ often supplied in media components
Microbes need balanced mixture of
nutrients. If an essential nutrients is in
short supply, microbial growth will be
limited
Requirements for Carbon, Hydrogen,
and Oxygen
All organisms need C,H,O & electron
 C – used to synthesize organic mol
 H & O – important element in organic mol
 Electron – electron transport & oxidation
reduction
 Requirement for C,H,O often satisfied
together
◦ carbon source often provides H, O, and
electrons


heterotrophs
◦ use organic molecules as carbon
sources – also obtain H,O & e- from
same mol. (which often also serve as
energy source)
◦ can use a variety of carbon sources

autotrophs
◦ use carbon dioxide as their sole or
principal carbon source
◦ Cannot b used as source of H,O & e◦ must obtain energy from other sources
Nutritional Types of Organisms
Biologist use specific term to define how
the requirements are fullfilled
 based on energy source
◦ phototrophs use light
◦ chemotrophs obtain energy from
oxidation of chemical compounds
(organic/inorganic)
 based on electron source
◦ lithotrophs use reduced inorganic
substances
◦ organotrophs obtain electrons from
organic compounds

Classes of Major Nutritional Types
Based on primary sources of carbon,
energy and electron
 majority of microorganisms known
◦ photolithoautotrophs
(photoautotrophs)

- Light energy, e- fro, reduced inorganic mol,
carbon sources is CO2
◦ chemoorganoheterotrophs
(chemoheterotrophs)
- energy from oxiation of organic/in compound,
e- from organic mol, C sources from organic
mol.
Requirements for Nitrogen,
Phosphorus, and Sulfur
needed for synthesis of important
molecules (e.g., amino acids, nucleic acids)
 phosphorus usually supplied as inorganic
phosphate
 sulfur usually supplied as sulfate via
assimilatory sulfate reduction

Sources of Nitrogen
organic molecules
 ammonia
 nitrate via assimilatory nitrate reduction
 nitrogen gas via nitrogen fixation

Sources of Phosphorus and Sulfur

phosphorus
◦ most organisms use inorganic phosphorus
which is directly incorporated into their cells

sulfur
◦ most organisms use sulfate and reduce it by
assimilatory sulfate reduction
Growth Factors
Some microbes require specific growth
factor to support growth
 organic compounds
 essential cell components (or their
precursors) that the cell cannot
synthesize
 must be supplied by environment if cell is
to survive and reproduce

Classes of Growth Factors
amino acids
◦ needed for protein synthesis
 purines and pyrimidines
◦ needed for nucleic acid synthesis
 vitamins
◦ function as enzyme cofactors
 Some microbes can synthesize many
growth factors eg vit
 Vit C (Gluconobacter) Vit D
(Saccharomyces)

Culture Media
culture media is solid or liquid preparation
need to grow, transport, and store
microorganisms in the laboratory
 must contain all the nutrients required by
the organism for growth
 Specialized media – isolation &
identification, antibiotic testing, water&
food analysis
 Majority need C,N,P,S, growth factor
 Some need precise composition



classification
◦ chemical constituents from which they are
made
◦ physical nature
◦ function
Chemical and Physical
Types of Culture Media
Defined or synthetic
 Complex

Defined or Synthetic Media
All chemical components are known
 liquid (broth)/ solid
 Use to culture photolitoautotrophs,
grown on medium contain CO2 (sodium
carbonate/bicarbonate)
 Chemoorganoheterotrophs- glucose as C
souces
 Used widely to know what the
microorganism is metabolizing

Complex Media
contain some ingredients of unknown
composition and/or concentration
 Single complex media may be sufficient to
meet all the nutrients requirement of
many microbes.
 Used to culture unknown nutritional
requirement of particular microbes, thus
defined medium cannot be constructed

Some complex Media Components

peptones
◦ protein hydrolysates prepared by partial
digestion of various protein sources

extracts
◦ aqueous extracts, usually of beef or yeast
◦ Beef extract contain a.acid, peptides,
nucleotides, organic acid, vit, mineral
◦ Yeast extract source of vit B, N and C

agar
◦ sulfated polysaccharide used to solidify liquid
media
◦ Extracted from red algae
◦ Microbes grow on agar can be incubated at
wide range of temp.
◦ Melt at 90°C
◦ most microorganisms cannot degrade it
Functional type of media
Functional Types of Media
supportive or general purpose media
◦ support the growth of many
microorganisms
◦ e.g., tryptic soy agar/broth
 enriched media
◦ general purpose media supplemented by
blood or other special nutrients
◦ e.g., blood agar (encourage growth of
fastidious microbes)

Selective media
 favor the growth of some microorganisms
and inhibit growth of others
 Bile salts/basic fuschin/crystal violet
suppress gram +ve , no effect on gram -ve
 e.g., MacConkey agar (bile salt), endo agar

◦ selects for gram-negative bacteria (E.coli)

Bacteria may also be selected by
incubation with nutrient they specifically
used
eg. Media contain cellulose
Differential media
 distinguish between different groups of
microorganisms based on their biological
characteristics
 e.g., blood agar (protein, carbo, iron, vit)

◦ hemolytic (streptococci) versus nonhemolytic
bacteria
◦ Produce clear zone- blood cell destruction

e.g., MacConkey agar (lactose, red dye)
◦ lactose fermenters versus nonfermenters
◦ Colony appear pink
Assignment
Find a journal about isolation and
characterization of microbes
 Explain:
1) reason for isolation done?
2)the technique used for isolation and
obtain a pure culture
3) growth media used for isolation and
selection of the microbes of interest; how
do they select microbes of interest
4) Method used for identification of
microbes of interest
