ch 6 Microbial Growth and Environmental Factors Flashcards

Vocabulary practice flashcards covering microbial growth rates, binary fission, growth phases, measurement methods, and environmental factors affecting growth.

Essential Nutrients

Chemical substances that must be provided to an organism because the organism cannot make these nutrients on its own.

Macronutrients

Nutrients required in large quantities that play principal roles in cell structure and metabolism, such as proteins, carbohydrates, and lipids.

Micronutrients

Trace elements required in small amounts involved in enzyme function and maintenance of protein structure, such as manganese, zinc, and nickel.

Microbial Growth

An increase in cell number within a population, rather than an increase in individual cell size.

Binary Fission

The method by which bacterial cells divide and clone themselves through cell elongation, DNA replication, plasma membrane constriction, cross-wall formation, and cell separation.

Generation Time

The time required for a population to double or complete a single fission cycle, typically around $20\text{--}30\text{ min}$.

Population Growth Equation

The equation $N_f = N_i \times 2^n$ used to calculate total cell count ($N_f$) from initial cell count ($N_i$) and generation number ($n$).

Lag Phase

The initial phase of bacterial growth where cells prepare for cell division with high metabolic activity, but no actual cell growth occurs.

Log Phase

The exponential growth phase characterized by rapid cell division via binary fission, where living cells outnumber dead cells.

Stationary Phase

A plateau phase in bacterial growth caused by limited nutrients, where the number of living cells equals the number of dead cells.

Death Phase

The phase characterized by rapid cell death due to lack of nutrients, resulting in dead cells outnumbering living cells.

Direct Count

A bacterial measurement method using a counting chamber that provides direct cell counts but cannot distinguish between living and nonliving cells.

Viable Count

A measurement technique (such as plate count or membrane filtration) that measures living viable colonies but cannot give a direct overall cell count.

Indirect Count

A measurement method using a spectrophotometer to assess bacterial growth via turbidity, which cannot determine direct cell counts or differentiate living from nonliving cells.

Psychrophiles

Cold-loving microorganisms that prefer temperatures between $-5^\text{o}\text{C}$ and $15^\text{o}\text{C}$.

Psychrotrophs

Cold-tolerant organisms preferring temperatures between $20^\text{o}\text{C}$ and $30^\text{o}\text{C}$ that can grow in refrigerators and cause food spoilage.

Mesophiles

Microorganisms that prefer moderate temperatures between $25^\text{o}\text{C}$ and $40^\text{o}\text{C}$, making them the group most likely to cause human disease at $37^\text{o}\text{C}$.

Thermophiles

Heat-loving microorganisms that prefer temperatures between $50^\text{o}\text{C}$ and $60^\text{o}\text{C}$.

Hyperthermophiles

Extreme heat-loving microorganisms that prefer temperatures greater than $80^\text{o}\text{C}$.

Acidophiles

Microorganisms that prefer acidic environments with pH values ranging from $0$ to $5$.

Neutrophiles

Microorganisms that prefer neutral environments with pH values ranging from $6$ to $8$.

Alkalophiles

Microorganisms that prefer basic environments with pH values greater than $9$.

Plasmolysis

The shrinkage of a cell's cytoplasm when placed in a hypertonic solution, causing the plasma membrane to pull away from the cell wall and inhibiting growth.

Extreme Halophiles

Organisms that thrive in high salt environments and require salt to live.

Facultative Halophiles

Organisms that do not require salt to live but can survive with or without it.

Chemotrophs

Organisms that gain energy from chemical compounds.

Phototrophs

Organisms that gain energy through photosynthesis.

Heterotrophs

Organisms that must obtain carbon in an organic form made by other living organisms.

Autotrophs

Organisms that use $\text{CO}_2$ as their carbon source and are not nutritionally dependent on other living things.

Superoxide Dismutase

An enzyme that detoxifies superoxide free radicals via the reaction $2\text{O}_2^-\text{`} + 2\text{H}^+ \rightarrow \text{H}_2\text{O}_2 + \text{O}_2$.

Catalase

An enzyme that removes hydrogen peroxide by converting it into water and oxygen gas via $2\text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_2$.

Peroxidase

An enzyme that removes hydrogen peroxide via $\text{H}_2\text{O}_2 + 2\text{H}^+ \rightarrow 2\text{H}_2\text{O}$ without producing oxygen gas.

Obligate Aerobes

Organisms that require oxygen to grow and cannot grow without oxygen.

Obligate Anaerobes

Organisms that cannot grow in the presence of oxygen and thrive in oxygen-free environments.

Facultative Anaerobes

Organisms that can grow with or without oxygen, but prefer to grow in the presence of oxygen.

Aerotolerant Anaerobes

Organisms that do not use oxygen for growth but can tolerate and grow in its presence.

Microaerophiles

Organisms that require a small amount of oxygen to grow.

Fastidious Bacteria

Bacteria that require many growth factors (such as vitamins and amino acids) from their environment to grow.

Candle Jar

A chamber where a burning candle consumes oxygen and produces carbon dioxide, creating low-oxygen and high-$\text{CO}_2$ conditions for microaerophile cultivation.