Microbial Growth

Vocabulary flashcards covering microbial physical and chemical growth requirements, biofilm features, culture preservation methods, and population growth curve dynamics from the lecture notes.

Psychrophiles

Cold-loving microorganisms with an optimum growth temperature of $15\,^\circ\text{C}$ that can grow at $0\,^\circ\text{C}$, typically inhabiting deep ocean waters and polar regions.

Psychrotrophs

Microorganisms that can grow at $0\,^\circ\text{C}$ with an optimum growth temperature between $20\,^\circ\text{C}$ and $30\,^\circ\text{C}$, primarily responsible for low-temperature food spoilage in refrigerators.

Mesophiles

Moderate-temperature-loving microorganisms with an optimum growth temperature around $25\,^\circ\text{C}$ to $40\,^\circ\text{C}$, encompassing most normal microbiota and human animal pathogens.

Thermophiles

Heat-loving microorganisms with an optimum growth temperature between $50\,^\circ\text{C}$ and $60\,^\circ\text{C}$, commonly found in hot springs and organic compost piles.

Hyperthermophiles

Extreme heat-loving microorganisms (extreme thermophiles) with an optimum growth temperature greater than $80\,^\circ\text{C}$, often living in deep oceanic depths.

Minimum Growth Temperature

The lowest temperature at which a specific microbial species will grow.

Optimum Growth Temperature

The temperature at which a microbial species demonstrates its maximum rate of growth.

Maximum Growth Temperature

The highest temperature at which microbial growth is possible.

Acidophiles

Microorganisms that grow remarkably well in acidic environments.

Plasmolysis

Shrinkage of a cell's cytoplasm away from its cell wall caused by osmotic water loss when placed in a hypertonic environment.

Extreme Halophiles

Also known as obligate halophiles, these organisms strictly require high salt concentrations (as high as $30\%\,\text{NaCl}$) for growth.

Facultative Halophiles

Organisms that do not require high salt concentrations to grow, but can tolerate salt levels between $2\%$ and $10\%\,\text{NaCl}$.

Trace Elements

Inorganic elements required in small amounts, such as iron, copper, molybdenum, and zinc, which function as enzyme cofactors in cells.

Obligate Aerobes

Microorganisms that strictly require oxygen to live and grow.

Facultative Anaerobes

Microorganisms capable of growing with or without oxygen, utilizing fermentation or anaerobic respiration when oxygen is unavailable.

Obligate Anaerobes

Microorganisms unable to use molecular oxygen for growth, with most being harmed by its presence.

Aerotolerant Anaerobes

Microorganisms that cannot use oxygen for growth, but tolerate its presence without being harmed.

Microaerophiles

Microorganisms that require oxygen for growth, but only at concentrations lower than that found in atmospheric air.

Organic Growth Factors

Essential organic compounds obtained directly from the environment, including vitamins, amino acids, purines, and pyrimidines.

Biofilm

A complex microbial community forming slime or hydrogels attached to surfaces, allowing cells to share nutrients and protect each other.

Quorum Sensing

A cell-to-cell communication process in bacteria within biofilms, involving the secretion of signaling chemicals (inducers) to attract other cells.

Planktonic

Refers to freely existing bacteria living as single individual cells rather than enmeshed or attached within a biofilm.

Deep-Freezing

A process of preserving bacterial cultures by freezing them at temperatures between $-50\,^\circ\text{C}$ and $-95\,^\circ\text{C}$ ($-54\,^\circ\text{C}$ to $-72\,^\circ\text{C}$).

Lyophilization

A preservation method where a bacterial culture is frozen and dehydrated in a vacuum (freeze-drying).

Binary Fission

The primary cell division process used by most bacteria where a cell elongates, replicates DNA, constricts, forms a cross-wall, and separates into two cells.

Budding

A mode of asexual bacterial division used by a few species where a cell forms a small initial outgrowth that enlarges and detaches.

Generation Time

Also known as doubling time, the time required for a bacterial cell to divide or for a population to double, ranging from $20\text{ minutes}$ to $24\text{ hours}$.

Bacterial Growth Curve

A graph plotting the $\log_{10}$ of the number of bacteria against time as a population progresses through distinct growth phases in liquid media.

Lag Phase

The phase of bacterial growth marked by intense metabolic activity and preparation for population growth, but showing little to no increase in cell number.

Log Phase

Also known as the exponential growth phase, a stage of rapid bacterial reproduction characterized by a logarithmic increase in population and constant minimum generation time.

Stationary Phase

A period of equilibrium in bacterial growth where microbial deaths balance the production of new cells as carrying capacity is approached.

Death Phase

The phase of bacterial growth where cell deaths exceed the production of new cells, causing the population to decrease at a logarithmic rate.