Microbiology Unit2: Microbial Physiology, Genetics, and In Vitro Growth Control

Comprehensive practice flashcards defining core terms and concepts across microbial physiology, genetics, environmental growth parameters, culture techniques, and physical and chemical control methods.

Microbial Physiology

The study of the vital life processes and functions of microorganisms.

Essential Nutrients

Chemical substances (primarily carbon, nitrogen, oxygen, phosphorus, and sulfur) required by an organism to construct vital macromolecules and sustain life.

Phototroph

An organism that utilizes light as its primary source of energy.

Chemotroph

An organism that uses inorganic or organic chemical compounds as its primary source of energy.

Chemolithotroph

An organism that oxidizes inorganic chemicals to obtain energy.

Chemoorganotroph

An organism that oxidizes organic chemicals to obtain energy.

Autotroph

An organism that uses carbon dioxide ($\text{CO}_2$) as its sole carbon source.

Heterotroph

An organism that utilizes organic compounds other than carbon dioxide as its source of carbon.

Photoautotroph

An organism that uses light as an energy source and carbon dioxide ($\text{CO}_2$) as a carbon source.

Photoheterotroph

An organism that utilizes light as an energy source and organic compounds other than $\text{CO}_2$ as its carbon source.

Chemoautotroph

An organism that derives energy from chemical compounds and uses carbon dioxide ($\text{CO}_2$) as a carbon source.

Chemoheterotroph

An organism that relies on chemical compounds for energy and organic compounds other than $\text{CO}_2$ for carbon, encompassing humans and all medically important bacteria.

Metabolic Enzymes

Biologic protein catalysts that enhance and regulate the rate of metabolic chemical reactions without being consumed or altered in the process.

Substrate

The specific chemical substance upon which a particular enzyme acts due to its unique 3D structure.

Catabolism

The series of metabolic reactions that break down larger complex molecules into smaller ones, releasing energy through bond cleavage; the primary source of cellular energy.

Anabolism

The series of metabolic reactions that synthesize larger macromolecules from smaller precursor molecules, requiring an input of energy to form chemical bonds.

Adenosine Triphosphate (ATP)

A high-energy molecule found in all living cells that stores and transfers energy between catabolic (energy-releasing) and anabolic (energy-consuming) reactions.

Glycolysis

A $9$-step biochemical pathway occurring in aerobic respiration that breaks down glucose into pyruvic acid, with each step governed by a specific enzyme.

Krebs Cycle

An $8$-step cyclic metabolic pathway in which acetyl-CoA condenses with oxaloacetate to generate citric acid, yielding $2\,\text{ATP}$, $\text{NADH}$, $\text{FADH}_2$, and $\text{H}^+$ ions before regenerating oxaloacetate.

Oxidative Phosphorylation

The process during the electron transport chain where ATP is generated from ADP coupled to electron transfer, yielding a net $36\text{--}38\,\text{ATP}$ per glucose molecule in aerobic respiration.

Cytochrome Oxidase

The enzyme within the electron transport chain responsible for transferring electrons to oxygen, the terminal electron acceptor.

Fermentation

An anaerobic metabolic pathway that converts glucose to pyruvic acid via glycolysis and then reduces pyruvic acid into organic end products without using oxygen, generating minimal energy.

Genotype

The complete collection of genetic material and genes possessed by an organism.

Phenotype

The observable physical traits, attributes, and physiological characteristics of an organism, directed by its genotype.

Constitutive Genes

Genes that are expressed at all times to maintain essential cellular functions.

Inducible Genes

Genes that are expressed only when their specific gene products are required by the cell.

Mutagen

A physical or chemical agent that increases the rate of DNA mutation above the spontaneous average rate of $1$ mutation per $10^6$ rounds of replication.

Lysogenic Conversion

A genetic process wherein temperate bacteriophage DNA integrates into a bacterial chromosome, replicating during fission and conferring new phenotypic properties.

Transduction

The transfer of bacterial DNA from one cell to another via a bacteriophage vector.

Transformation

The genetic alteration of a bacterial cell resulting from the direct uptake and incorporation of foreign DNA fragments from the surrounding environment.

Conjugation

The transfer of genetic material (such as a plasmid) between two bacterial cells via direct cell-to-cell contact through a specialized sex pilus.

Genetic Engineering

The transfer of eukaryotic (especially human) genes into easily cultured cells to facilitate the commercial production of vital proteins like HGH, insulin, and interferon.

Gene Therapy

The insertion of a normal, functional gene into cells to correct a specific acquired or inherited disorder caused by a defective gene.

In Vitro vs. In Vivo

In vitro refers to biological events occurring outside the living organism (such as in laboratory culture), whereas in vivo refers to events occurring inside a living body.

Thermophiles

Microorganisms that grow optimally at high temperatures, frequently found in habitats such as hot springs, compost pits, and hydrothermal vents.

Mesophiles

Microorganisms that grow best at moderate temperatures, including human body temperature ($37^\circ\text{C}$), which encompasses most human pathogens.

Psychrophiles

Cold-adapted microorganisms that thrive in environments such as cold ocean waters and high altitudes, surviving at temperatures as low as $-13^\circ\text{C}$.

Osmotic Pressure

The hydrostatic pressure exerted on a cell membrane caused by solute concentration gradients between the intracellular cytoplasm and the extracellular environment.

Hypertonic Solution

An environment with a higher solute concentration than the cytoplasm, causing water to flow out of the bacterial cell and induce plasmolysis.

Halophiles

Microorganisms that thrive in and require high-salinity environments for growth.

Generation Time

The time required for a bacterial cell to undergo binary fission and divide into two cells, ranging from $20\,\text{minutes}$ to $24\,\text{hours}$ or more.

Bacterial Colony

A macroscopic mound of millions of bacterial cells visible on a solid agar surface, derived from the clonal proliferation of an initial cell or cluster.

Chemically Defined Medium

A synthetic culture medium in which all ingredients and their exact chemical concentrations are known.

Complex Medium

A culture medium containing digests or extracts from animal tissue, plants, yeast, or fish whose precise chemical formulation is undefined.

Enriched Medium

A nutrient-abundant medium supplemented with specific growth factors to cultivate fastidious microorganisms.

Selective Medium

A culture medium containing inhibitory agents that suppress the growth of unwanted organisms while permitting the proliferation of the target organism.

Differential Medium

A growth medium containing indicators that distinguish between different microbial species based on biochemical differences, usually producing visible color changes.

Aseptic Technique

Procedures executed to prevent contamination of cultures, clinical specimens, and the work environment, while protecting lab personnel from infection.

Spectrophotometry

A method measuring culture turbidity by determining the transmission of light through a liquid sample to estimate bacterial population densities.

Viable Plate Count

A quantitative culture method involving serial dilution plating where plates containing $30\text{--}300$ colonies are counted and multiplied by the dilution factor to determine live bacteria per milliliter.

Bacterial Population Growth Curve

A logarithmic plot representing the four distinct phases of bacterial population growth in closed liquid culture over time.

Lag Phase

The initial growth curve phase where bacteria absorb nutrients and synthesize enzymes to prepare for division without an increase in population size.

Logarithmic (Log) Phase

The rapid growth phase during which bacteria multiply exponentially, doubling in number with each generation time.

Stationary Phase

The plateau phase in which nutrient depletion and toxic metabolic waste accumulation cause the rate of cell division to equal the rate of cell death.

Death (Decline) Phase

The terminal phase of a bacterial growth curve where cells die rapidly due to severe overcrowding and accumulation of toxic wastes.

Sterilization

The complete destruction or removal of all forms of microbial life, including vegetative cells and resistant bacterial endospores.

Disinfection

The elimination of most or all pathogenic microorganisms from inanimate, non-living surfaces and objects.

Antiseptics

Chemical solutions formulated to disinfect living tissues and skin without penetrating deep into hair follicles or pores.

Sanitization

The reduction of microbial populations on surfaces to levels deemed safe by public health regulations.

Microbicidal Agents

Physical or chemical agents ending in the suffix '-cide' that kill microorganisms directly (e.g., bactericidal, sporicidal, viricidal).

Microbistatic Agents

Chemical substances or drugs that inhibit microbial growth and reproduction without necessarily killing the organisms.

Lyophilization

A preservation method that combines freezing and dehydration (freeze-drying) to place microbes into suspended animation for long-term storage.

Autoclave

A moist-heat sterilizing device that uses pressurized steam, typically operating at $15\,\text{PSI}$ and $121.5^\circ\text{C}$ for $20\text{--}40\,\text{minutes}$, to kill all microbial life.

Cytochrome Oxidase

The enzyme within the electron transport chain responsible for transferring electrons to oxygen, the terminal electron acceptor.

Osmotic Pressure

The hydrostatic pressure exerted on a cell membrane caused by solute concentration gradients between the intracellular cytoplasm and the extracellular environment.

Hypotonic Solution

An environment where the extracellular solute concentration is lower than that inside the cell, causing water to flow into the cell by osmosis.

Isotonic Solution

An environment where the solute concentration is equal inside and outside the cell, resulting in no net movement of water across the cell membrane.

Generation Time

The time required for a bacterial cell to undergo binary fission and divide into two cells, ranging from $20\,\text{minutes}$ to $24\,\text{hours}$ or more.

Dry Heat Sterilization

A physical method of sterilization that destroys microorganisms through processes such as baking ($160\text{--}165^\circ\text{C}$ for $2\,\text{hours}$ or $170\text{--}180^\circ\text{C}$ for $1\,\text{hour}$), incineration, or direct flaming.

Moist Heat Sterilization

A physical method that coagulates cellular proteins through pressurized steam, killing all forms of microbial life at lower temperatures and faster rates than dry heat.

Chemical Sterilization

A method using agents such as ethylene oxide gas or specialized liquid chemical sterilants to destroy all microbes on heat-sensitive materials.

Microbistatic Agents

Chemical substances or drugs that inhibit microbial growth and reproduction without necessarily killing the organisms.

Lyophilization

A preservation method that combines freezing and dehydration (freeze-drying) to place microbes into suspended animation for long-term storage.

Autoclave

A moist-heat sterilizing device that uses pressurized steam, typically operating at $15\,\text{PSI}$ and $121.5^\circ\text{C}$ for $20\text{--}40\,\text{minutes}$, to kill all microbial life.