Chapter 6
Requirements for MO growth
1) Nutrient requirements for all life forms
2) Nutritional patterns
3) Physical and chemical requirements
1) Nutrient requirements:
macroelements (>98% dry wt)
• CHOPKNSCaFeMg =
– “see hopkins café,
mmmmgood”
• 6 needed in g/Liter conc.
–
–
–
–
–
CHONPS
sugars = CHO
protein = CHONS
nucleic acids = CHONP
lipids = CHOP
-others in mg/Liter conc….
Nutrient requirements:
microelements (trace elements)
• MgBMnMoCuZnCl (Na)
“managed by Marilyn
Monroe’s cousin
Clarence…naaah!”
• Needed in low conc.
(ug/Liter)
• Used as enzyme cofactors
Prototrophs vs Auxotrophs
• Nutrient req exhibited by the
majority of the species =
prototrophs
– Also referred to as “wild-type”
strains
• Certain mutations/ changes in
the DNA can lead to
nutritional impairment =
auxotroph strains
– Produces fastidious line of MO
– Many need nutritional
supplements added to media
• Organic growth factors
2) Nutritional patterns exhibited by
life forms
• Carbon Source: if CO2 provides C, autotroph; if
organic provides, heterotroph
• Energy Source: if provided from light, phototroph;
if from organic, chemotroph
• Four possible permutations of carbon/energy sources:
•
•
•
•
Photoautotroph
Photoheterotroph
Chemoautotroph
Chemoheterotroph
photoautotrophs
• CO2 + H2O  (CH2O)n + O2
– Oxygenic PS
• CO2 + H2S  (CH2O)n + S2
– Anoxygenic PS
photoheterotrophs
• Light energy + organic
carbon source
• Organic  CO2 + H2O
• Purple and green nonsulfur bacteria
The white area of the channel is too hot for photosynthetic life, but as the
water cools along a gradient, the colored phototrophic bacteria colonize and
ultimately construct the colored microbial mats composed of a consortium of
photosynthetic microorganisms
.
chemoheterotrophs
• Organic carbon and energy
source
• Majority of bacteria and
MO’s studied in this course
• Organic + O2  CO2 +
H2O (aerobes)
• Organic  organic
acids/ethanol + CO2 (ferm)
• Organic + ___ 
(anaerobes)
chemoautotrophs
• Inorganic energy source
+ CO2 C source
Nitrifying bacteria inside these polymer gel pellets
remove ammonia from swine wastewater.
– Nitrifying bacteria
– Sulfur oxidizers
• Good and bad for the
environment!
3) Physical and chemical
requirements for life
• Temperature categories:
– Psychrophile
– Mesophile
– Thermophile
Figure 6.1
• Within each category are
the ‘cardinal temperature’
values:
– minimum – optimum - maximum
Temperature and food safety
Figure 6.2
pH and microbial life
• Acidophiles - <5.0
• Neutrophiles – 5.5 – 8.5
• Alkalinophiles - >8.5
Osmotic pressure
• Hypertonic enviro’s
draw water out of
cells
– Bacterial cells
contain hypertonic
cytoplasmic
contents
– Many foods are
preserved in salt or
sugar
Requirement for O2
• O2 forms harmful free
radicals of O2(superoxide) inside
cells
• Combined effort of 2
enzymes de-toxifies
free radicals
– Superoxide dismutase
– Catalase or peroxidase
O2- + O2- + 2H+  H2O2 + O2…….SOD
2H2O2  2H2O + 2O2 … catalase