Microbial Growth & Nutrition Flashcards by Cza S.

Requirements for microbial growth can be divide into two main categories:

Physical
Chemical

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▪ Temperature
▪ pH
▪ Osmotic pressure

Physical

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▪ Sources of carbon
▪ Nitrogen
▪ Sulfur
▪ Phosphorus
▪ Oxygen
▪ Trace elements,
▪ Organic growth factors

Chemical

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Physical Requirements of microbial growth & nutrition

Temperature Requirement
pH Requirement (Most grow best between pH 6.5 and 7.5
Osmotic Pressure
Other Physical Requirements

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Lowest temperature at which the species will grow

Minimun growth temperature

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Temperature at which the species grows best

Optimum growth temperature

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Highest temperature at which growth is possible

Maximum growth temperature

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True or false:

Most organisms are mesophilic

True

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Temperature which is optimal for many free-living forms, and the body temperature of the host is optimal

30 degrees celsius (35-37 degrees celsius)

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Lowest or minimum time required to kill organism under constant temperature

Thermal death time

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Lowest temperature required to kill microorganism in a constant time

Thermal death point

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▪ Cold-loving microbes
▪ Grow well 0°C to a maximum of 20°C
▪ Example:
❖ Listeria monocytogenes
❖ Yersinia enterolitica

Psychrophiles/Cryophiles

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▪ Temperature optimum between 20°C and 30°C but grow well at lower temperatures
▪ Important cause of food spoilage

Psychrotrophs

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▪ Moderate-temperature-loving microbes
▪ 20°C to 40°C (30°C-37°C)
▪ Most commonly encountered pathogenic bacteria in the clinical laboratory

Mesophiles

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▪ Heat-loving microbes
▪ 50°C to 60°C
▪ Example: Bacillus stearothermophilus

Thermophiles

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Above the temperature of boiling water

Hyperthermophilic

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

Extremophiles

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Incubation Temperature of Most Bacteria and Most Viruses

35-37C

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Incubation Temperature of fungi

28-30C

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Incubation Temperature of Aerobes

35-37C for 18-24 hrs

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Incubation temperature of Anaerobes

35-37C for 24-48 hrs

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Incubation temperature of Anaerobes

35-37C for 24-48 hrs

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Diagnostic Laboratory Incubate Cultures for Bacterial Growth at:

(Temperature)

35-37C

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PAE and Campylobacter can grow at:
(Temperature)

35-37C and 42C

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Diagnostic laboratory usually incubates cultures for bacterial growth at

35°C

Pseudomonas aeruginosa and Campylobacter can grow at

35°C and 42°C

▪ pH 6.0–8.0 ▪ Maintain an internal pH of about 7.5 over an external range of 5.5–8.5

Neutralophiles

▪ As low as pH 3.0 (6.5-7) ▪ Maintain an internal pH of about 6.5 over an external range of 1.0–5.0

Acidophiles

▪ As high as pH 10.5 (8.4-9) ▪ Maintain an internal pH of about 9.5 over an external range of 9.0–11.0

Alkaliphiles

Peptones and amino acids in media act as _________

Buffers

Exhibiting their buffering effect in the pH growth range of most bacteria

Phosphaste salts

Culture media for bacterial isolation are usually adjusted to a final pH between __________

7.0 to 7.5

Culture media for bacterial isolation are usually adjusted to a final pH between __________

7.0 to 7.5

Organisms requiring high osmotic pressures

Osmophilic

Organisms that grow rapidly in high-pressure environment (600 to 1100 atm pressure) ▪ Example: ❖ Shewanella ❖ Colwellia ❖ Photobacterium

Barophiles

Shrinkage of the cell's cytoplasm

Plasmolysis

Other Physical Requirements of bacterial growth and nutrition

Salt concentration Moisture

Organisms requiring high salt concentrations ❖ Example: Staphylococcus aureus Listeria monocytogenes All Vibrio species except: V. mimicus and V.cholerae

Halophilic

High salt concentrations that they actually require them for growth

Extreme Halophiles/Obligate Halophiles

Do not require high salt concentrations but are able to grow at salt concentrations up to 2%

Facultative Halophiles

Vital for bacterial growth and susceptibility testing

Moisture

Three Major Nutritional Needs for Growth

Source of Carbon Source of Nitrogen Source of Energy

o Carbon → 50% of the dry weight of a bacterium o Making cellular constituents

Source of Carbon

o Nitrogen → 14% of the dry weight o Making proteins

Source of Nitrogen

ATP → performing cellular functions

Source of Energy

Nucleic acids and phospholipids of cell membranes

Phosphate

Pretein synthesis

Sulfur

Make up up an additional 4% of the weight

Phosphate and sulfur

Mineral ions

Na+ K+ Cl- Ca

CARBON SOURCE of bacteria

Heterotrophs (Organotrophs) Autotrophs (Lithotrophs)

o Require organic carbon for growth o Use reduced, preformed, organic molecules from other bacteria

Heterotrophs (Organotrophs)

Get most of their carbon from the source of their energy -proteins, carbohydrates, and lipids

Chemoheterotrophs

o Use CO2 as the sole source of carbon o Do not require organic nutrients for growth

Autotrophs (Lithotrophs)

Derive their carbon from carbon dioxide

Chemo autotrophs and Photoautotrophs

Use an inorganic substrate such as hydrogen or thiosulfate as a reductant and carbon dioxide as a carbon source

Chemolithotrophs

sole nitrogen source

NH3

sole nitrogen source

NH3

o Ability to assimilate N2 reductively via NH3 o Requires a large amount of metabolic energy and is readily inactivated by oxygen

Nitrogen Fixation

Production of NH3 from the deamination of amino acids

Ammonification

Ability to assimilate nitrate (NO3-) and nitrite (NO2-) reductively by conversion of these ions into NH3

Assimilatory nitrate reduction and assimilatory nitrite reduction

Conversion of NH3 to gaseous N2 under anaerobic conditions

Denitrification

o Component of ATP, nucleic acids, and such coenzymes as NAD, NADP, and flavins o Assimilated as free inorganic phosphate (Pi)

Phosphate

• Autotrophic bacteria can oxidize it to sulfate • Most microorganisms can use sulfate as a 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

SULFUR SOURCE

• Magnesium Ion (Mg²⁺) and Ferrous Ion (Fe²⁺) o Enzyme function • Mg²⁺ and K⁺ o Function and integrity of ribosomes • Ca²⁺ o Constituent of gram-positive cell walls • Other minerals: Mn²⁺, Mo²⁺, Co²⁺, Cu²⁺, and Zn²⁺

Mineral source

• Organic compound that a cell must contain to grow but that it is unable to synthesize • Substances that are required by fastidious bacteria for their growth and multiplication • Example: Amino acids, purines, pyrimidines and vitamins, hemoglobin, pentose, fatty acids

Growth factors

Do not require exogenous sources of growth factors since they synthesize their own

Prototrophics

Require the addition of growth factors to culture media for growth to occur

Auxotrophics

True or false: All bacteria that inhabit the human body fall into the heterotrophic or organotrophic group

True

True or false: Fastidious bacteria require additional substances such as vitamins, purines, pyrimidines, and hemoglobin for growth and survival

True

True or false: Saprophytes does not require dead organic substances

False. Saprophytes require dead organic substances

Oxygen Requirement of bacteria

Aerobes Anaerobes

Grow in the presence of oxygen

Aerobes

Grow in the absence of atmospheric oxygen

Anaerobes

o 21% oxygen and 0.03% CO₂ o Incubation in air or an anaerobic incubator with 10% carbon dioxide presents satisfies their oxygen requirement o Example: Bordetella, Brucella, Mycobacteria, Pseudomonas

Obligate Aerobe

o Can use oxygen when it is present but are able to continue growth by using fermentation or anaerobic respiration when oxygen is not available o Example: Enterobacteriaceae

Facultative Aerobes

o Require a reduced level of oxygen to grow o 2%–10% oxygen o Generated in culture jars or pouches using a commercially available microaerophilic atmosphere-generating system o 5% O₂, 10% CO₂, 85% N₂ o Example: ▪ Campylobacter spp. → requires 5% to 6% oxygen ▪ Treponema pallidum

Microaerophiles

o Can grow in its presence, but they do not use it as a hydrogen acceptor o Ferment carbohydrates to lactic acid o Example: Lactobacilli, Propionibacterium acnes

Aerotolerant anaerobes (Facultative Aerobes)

● bacteria that are unable to use molecular oxygen for energy-yielding reactions ● lack both superoxide dismutase and catalase ● 0% O, 5-10% CO2, 80-90% N2, 5-10% H2 ● Example: Clostridium, Bacteroides

Obligate Anaerobes

Contain Superoxide dismutase and Catalase that counter the toxic effects of oxygen

Obligate Aerobes and Facultative Anaerobes

● organisms grow best when the atmosphere is enriched with extra carbon dioxide ● 15% O, 5% to 10% CO2 (CO2 incubator or bags); 3%CO2 (Candle jars) ● Example: HACEK, Neisseria gonorrhoeae

Capnophilic

Diagnostic microbiology laboratories often maintain their aerobic incubators at a ___________ carbon dioxide level

5% to 10%

Most aerobic and facultative bacteria need _________

0.03% CO2

time required for one cell to divide into two cells

GENERATION TIME / DOUBLING TIME

Generation time: ____________ for a fast-growing bacterium such as E. coli

20 minutes

Guu

Uou

• Pseudomonas aeruginosa • Nocardia • Bacillus • Mycobacterium • Corynebacterium

Obligate Aerobes

• Actinomyes • Bacteroids • Clostridium • Fusobacterium • Eubacterium • Prevotella

Obligate Anaerobes

• Lactobacillus • Propionibacterium

Aerotolerant

• Campylobacter • Helicobacter • Borrelia burgdorferi

Microaerophiles

Growth occurs only where high concentrations of oxygen have diffused into the medium

Obligate aerobes

Growth is best where most oxygen is present, but occurs throughout tube

Facultative anaerobes

Growth is best where most oxygen is present, but occurs throughout tube

Facultative anaerobes

Growth occurs only where there is no oxygen

Obligate anaerobes

Growth occurs evenly; oxygen has no effect

Aerotolerant anaerobes

Growth occurs only where a low concentration of oxygen has diffused into medium

Microaerophiles

Only aerobic growth; oxygen required

Obligate aerobes

Both aerobic and anaerobic growth; greater growth in presence of oxygen

Facultative anaerobes

Only anaerobic growth; ceases in presence of oxygen

Obligate anaerobes

Only anarobic growth; but continues in presence of oxygen

Aerotolerant anaerobes

Only aerobic growth; oxygen required in low concentration

Microaerophiles

Microbial Growth & Nutrition Flashcards

(100 cards)