Microbial Growth & Nutrition Flashcards
Requirements for microbial growth can be divide into two main categories:
Physical
Chemical
▪ Temperature
▪ pH
▪ Osmotic pressure
Physical
▪ Sources of carbon
▪ Nitrogen
▪ Sulfur
▪ Phosphorus
▪ Oxygen
▪ Trace elements,
▪ Organic growth factors
Chemical
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
Lowest temperature at which the species will grow
Minimun growth temperature
Temperature at which the species grows best
Optimum growth temperature
Highest temperature at which growth is possible
Maximum growth temperature
True or false:
Most organisms are mesophilic
True
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)
Lowest or minimum time required to kill organism under constant temperature
Thermal death time
Lowest temperature required to kill microorganism in a constant time
Thermal death point
▪ Cold-loving microbes
▪ Grow well 0°C to a maximum of 20°C
▪ Example:
❖ Listeria monocytogenes
❖ Yersinia enterolitica
Psychrophiles/Cryophiles
▪ Temperature optimum between 20°C and 30°C but grow well at lower temperatures
▪ Important cause of food spoilage
Psychrotrophs
▪ Moderate-temperature-loving microbes
▪ 20°C to 40°C (30°C-37°C)
▪ Most commonly encountered pathogenic bacteria in the clinical laboratory
Mesophiles
▪ Heat-loving microbes
▪ 50°C to 60°C
▪ Example: Bacillus stearothermophilus
Thermophiles
Above the temperature of boiling water
Hyperthermophilic
Prokaryotes that are able to survive in unusual conditions like the absence of oxygen, increased temperatures, and living below the earth’s surface
Extremophiles
Incubation Temperature of Most Bacteria and Most Viruses
35-37C
Incubation Temperature of fungi
28-30C
Incubation Temperature of Aerobes
35-37C for 18-24 hrs
Incubation temperature of Anaerobes
35-37C for 24-48 hrs
Incubation temperature of Anaerobes
35-37C for 24-48 hrs
Diagnostic Laboratory Incubate Cultures for Bacterial Growth at:
(Temperature)
35-37C
PAE and Campylobacter can grow at:
(Temperature)
35-37C and 42C
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
