PHYSICAL REQUIREMENTS OF MICROORGANISMS Flashcards
Temperature meaning (3)
Great influence on growth since growth is
dependent on chemical reactions that are
affected by temperature
Also affects reproduction, morphology,
metabolic processes & nutritional
requirements
Microorgs grow over a broad range of
temperature
3 types of cardinal temperature for growth of microorganisms
Minimum
Optimum
Maximum
lowest temp in which microbes can grow
Minimum
temp in which microbes best grow
Optimum
highest temp in which microbes can grow
Maximum
Transport process slow growth cannot occur
Membrane gelling
Collapse of cytoplasmic membrane ; thermal lysis
Protein denaturation
Occuring at increasingly rapid rates
Enzymatic reactions
Psychrophiles (3)
Cold-loving;
grow best at 15-20 °C
e.g. genera of Pseudomonas, Flavobacterium, Alcaligenes
Mesophiles (3)
Moderate-temerature-loving
grow best at 25-40 °C
e.g. Most microorganisms
Thermophiles 4
Heat-loving
grow best at 50-60°C
E.g. microbes in volcanic areas, compost heaps, hot springs
No eukaryotes grow at > 60 °C
Group of microorganism based on tempt range
Psychrophiles Mesophiles Thermophiles
Physiological Groups based on Responses to
Oxygen 4
Aerobes, Facultatives, Anaerobes, Microaerophiles
Aerobes 2
Require O2
(21 % in a standard air)
e.g. Molds, Mycobacterium, Legionella
Facultatives (2)
Can grow w/(aerobic) or w/o air (Anaerobic)
E.g. Enterobacteriaceae (e.g. E. coli), many yeasts
(e.g. Saccharomyces cerevisiaea)
yielding processes; obtain
energy by fermentation under anaerobic condition
O2
due to certain molecules
produced during reactions involving O2 (eg.
superoxide radical, hydrogen peroxide, hydroxyl
radicals – damage cells & destroy vital
components like DNA)
Toxicity to O2
Cannot grow in air and do not use O2
for E
production
e.g. Clostridium
Anaerobes
Limited tolerance due to susceptibility to
superoxide dismutase & hydrogen peroxide formed
in cultures under aerobic condition
Microaerophiles
Can use O2
for E-yielding reactions but grow best
at 1-15% O2
in standard air
Microaerophiles
Campylobacter jejuni as an example of
Microaerophiles
Toxic forms of oxygen (4)
Superoxide, hydro perox, hydroxyl radical
Water
The force with which water moves through the
cytoplasmic membrane from a solution of high
solute concentration to a solution of low solute
concentration
Osmotic pressure
solute-loving microbes (eg.
Microbes in the ocean)
Halophiles
pressure exerted by water
on cells by the weight of the water resting on top
of them
Hydrostatic Pressure
pressure-dependent microbes (eg.
microbes in the ocean floor)
Barophiles
