Unit 4. Microbial Growth & Nutrition

• physical (temperature, pH, osmotic pressure)

• chemical

two requirements for microbial growth

• Listeria monocytogenes

• Yersinia enterolitica

• Pseudomonas fluorescens

• Serratia liquefaciens

ex. of Psychrophiles/Cryophiles

Psychrophiles/Cryophiles

cold-loving microbes; living in arctic regions

Pseudomonas fluorescens

ex. of Psychrotrophs

Psychrophiles / Cryophiles

the type of bacteria that is usually present in blood product contaminant in cold environment.

Mesophiles

Moderate-temperature-loving microorganisms that grow best between 20°C and 40°C, especially at 30°C–37°C.

Psychrotrophs

type of bacte. that is important cause of food spoilage

Mesophiles

Most pathogenic bacteria encountered in the clinical laboratory belong to this group.

0°C–20°C.

Psychrophiles temperature range

20°C–30°C, but can also grow at refrigerator temperatures

Psychrotroph optimum temperature

20°C–40°C (best at 30°C–37°C).

Mesophiles temperature range

50°C–60°C.

Thermophiles temperature range

Above 100°C.

Hyperthermophiles temperature range

Thermophiles

Heat-loving bacteria

• Pseudomonas aeruginosa

• Campylobacter jejuni

• Helicobacter pylori

• Mycobacterium xenopi

ex. of bacteria that grows best at 42°C

Extremophiles

prokaryotes that are able to survive in unusual conditions like the absence of oxygen, increased temperatures, and living below the earth’s surface

Thermophiles

heat-loving microbes

Bacillus stearothermophilus

ex. of Thermophiles

Pyrococcus fumaris

ex. of Hyperthermophiles

30°C-37°C (35-37 °C)

what is the basis of temperature of incubator

Bacillus stearothermophilus - kilit ampule

what is the biological indicator used in the QC of autoclave

MINIMUM GROWTH TEMPERATURE

lowest temperature at which the species will grow

OPTIMUM GROWTH TEMPERATURE

temperature at which the species grows best

MAXIMUM GROWTH TEMPERATURE

highest temperature at which growth is possible

Thermal Death Time

lowest or minimum time required to kill an organism under constant temperature

Thermal Death Point

lowest temperature required to kill microorganism in a constant time

6.5 and 7.5

most bacteria grow best in a narrow pH range near neutrality, between pH _____________.

7.0 - 7.5

culture media is adjusted at pH lvl. of ______

6.0–8.0.

Optimum pH of neutralophiles

• 7.5

• 5.5-8.5

Neutralophiles

• internal pH

• external range

Acidophiles

have optima as low as pH3.0 (6.5-7)

• 6.5

• 1.0-5.0

Acidophiles

• internal pH

• external range

Lactobacillus acidophilus

• tomato juice agar (acidic)

Acidophiles example

Alkaliphiles

have optima as high as pH 10.5 (8.4-9)

• 9.5

• 9.0-11.0

Alkaliphiles

• internal pH

• external range

Vibrio cholerae

• alkaline peptone water medium

Alkaliphiles example

PEPTONES ; AMINO ACIDS

____________ and ______________ in media act as BUFFERS

Osmophilic

organisms requiring high osmotic pressures

Barophiles

organisms that grow rapidly in high-pressure environment (600 - 1100 atm pressure)

• Shewanella,

• Colwellia,

• Photobacterium

ex of Barophiles

Plasmolysis

Shrinkage of the bacterial cytoplasm due to water loss in a hypertonic environment.

Halophilic

Microorganisms that require high salt concentrations for growth.

• Staphylococcus aureus

• Listeria monocytogenes,

• all Vibrio spp except V.mimicus and V.cholerae

ex of Halophiles

Extreme Halophiles / Obligate Halophiles

Organisms that require high salt concentrations for survival and growth.

Facultative Halophiles

Organisms that do not require high salt but can tolerate and grow in concentrations up to about 2% NaCl.

Moisture

An essential physical factor required for bacterial metabolism, growth, and susceptibility testing.

• carbon

• nitrogen

• energy (ATP)

ENUMERATE

three major nutritional needs for growth of bacteria

inorganic phosphate (Pi).

Phosphorus is obtained as__________________.

Carbon

Makes up about 50% of the dry weight of bacteria and is used to synthesize cellular constituents.

Nitrogen

Makes up about 14% of the dry weight of bacteria and is required for proteins and nucleic acids.

Makes up cellular components

ATP

The primary energy source used to perform cellular functions.

Phosphate

Component of ATP, nucleic acids, phospholipids, NAD, NADP, and flavins.

Nucleic acids and phospholipids of cell membranes

Sulfur

Required for protein synthesis

4%

Phosphate and Sulfur make up an additional ___ of the weight

Mineral Ions

Essential inorganic ions such as Na⁺, K⁺, Cl⁻, Ca²⁺, Mg²⁺, and Fe²⁺ that support bacterial growth and metabolism.

Heterotrophs (Organotrophs)

Organisms that require organic carbon compounds for growth.

Heterotrophs (Organotrophs)

use reduced, performed, organic molecules from other bacteria

Chemoheterotrophs

Organisms that obtain both carbon and energy from organic compounds such as proteins, carbohydrates, and lipids.

Autotrophs (Lithotrophs)

Organisms that use CO₂ as their sole carbon source. Do not require organic nutrients for growth

Chemoautotrophs

Autotrophs that obtain energy from chemical reactions while using CO₂ as their carbon source.

Photoautotrophs

Autotrophs that obtain energy from light while using CO₂ as their carbon source.

Chemolithotrophs

Organisms that obtain energy from inorganic chemicals (e.g., hydrogen or thiosulfate) and use CO₂ as their carbon source.

NH3 (ammonia)

sole nitrogen source

for protein synthesis → nucleoid

Nitrogen Fixation

Conversion of atmospheric N₂ into NH₃ for cellular use;

requires high energy and is inhibited by oxygen.

Nitrogen Fixation

• ability to assimilate N2 reductively via NH3

• requires a large amount of metabolic energy

oxygen

Nitrogen Fixation is readily inactivated by ________

Ammonification

Production of NH₃ through the deamination of amino acids.

Assimilatory nitrate reduction

Conversion of NO₃⁻ into NH₃ for incorporation into cellular components.

Assimilatory nitrite reduction

Conversion of NO₂⁻ into NH₃ for incorporation into cellular components.

Denitrification

conversion of NH3 to gaseous N2 under anaerobic conditions.

SULFUR SOURCE

• autotrophic bacteria can oxidize it to sulfate

• most microorganisms can use sulfate as sulfur source, reducing the sulfate to the level of hydrogen sulfide (H₂S)

• some microorganisms can assimilate H2S directly from the growth medium

• sources: sulfate ion, hydrogen sulfide, sulfur-containing amino acids

Magnesium Ion (Mg²⁺) and Ferrous Ion (Fe²⁺)

Required for enzyme function.

Mg²⁺ and K⁺

Maintain ribosome function and integrity.

Ca²⁺

Important constituent of Gram-positive cell walls.

Growth factors

Organic compounds required for growth that some bacteria cannot synthesize.

fastidious bacteria

Growth Factors are substances that are required by _______________ for their growth and multiplication

• Amino Acids,

• Purines,

• Pyrimidines and Vitamins,

• Hemoglobin,

• Pentose,

• Fatty Acids

ex of GFs

Prototrophics

bacteria that do not require exogenous source of growth factor since they synthesize their own

non-fastidious

Auxotrophics

bacteria that require the addition of growth factor to culture media for growth to occur

fastidious

heterotrophic or organotrophic

all bacteria that inhabit the human body fall into the ______________________ group

Saprophytes

Organisms that obtain nutrients from dead organic matter.

• Micrococcus

• Pseudomonas.

es of saprophytes

Obligate aerobes

Bacteria that require oxygen for growth because they use it as the final electron acceptor in aerobic respiration.

• Pseudomonas.

• Bordetella,

• Brucella,

• Mycobacterium,

[Pres BBM!]

ex of obligate aerobes

Facultative anaerobes

Bacteria that use oxygen when available but can switch to fermentation or anaerobic respiration when oxygen is absent.

Enterobacteriaceae

Example of facultative anaerobes

Enterobacteriaceae

Bacteria that are most commonly isolated pathogens

Microaerophiles

Bacteria that require reduced oxygen concentrations (2–10% O₂) for growth.

• Campylobacter spp.

• Treponema pallidum.

Examples of microaerophiles

Obligate anaerobes

Bacteria that cannot use molecular oxygen and are harmed or killed by it.

• Clostridium

• Bacteroides.

Examples of obligate anaerobes

Aerotolerant anaerobes (Facultative Aerobes)

Bacteria that do not use oxygen for energy production but can survive and grow in its presence by relying on fermentation.

Aerotolerant anaerobes (Facultative Aerobes)

can grow in the presence of oxygen, but they do not use it as a hydrogen acceptor

ferment carbohydrates to lactic acic

• Lactobacillus

• Cutibacterium acnes (Propionibacterium acnes)

Examples of (Aerotolerant Anaerobes) Facultative Anaerobes

Obligate Aerobes and Facultative Anaerobes

Superoxide dismutase

Catalase

Contain ______________ and _________ that counter the toxic effects of oxygen

Thioglycollate medium

A reducing medium that removes dissolved oxygen and creates an oxygen gradient for culturing bacteria with different oxygen requirements.

Superoxide dismutase (SOD)

Enzyme that converts toxic superoxide radicals into hydrogen peroxide.

Catalase

Enzyme that converts hydrogen peroxide into water and oxygen.

Obligate aerobes and facultative anaerobes.

Which bacteria contain SOD and catalase?

Obligate anaerobes.

Which bacteria lack SOD and catalase?