Nutrition, Cultivation, and Growth of Microorganisms

Comprehensive vocabulary flashcards covering microbial growth kinetics, environmental physical parameters (temperature, pH, osmolarity, oxygen), chemical and physical antimicrobial control, and therapeutic mechanisms of antibacterials, antivirals, and antifungals.

Exponential Growth

A pattern of microbial population growth in which cell numbers double within a specific, constant time interval.

Generation Time

The duration of time required for a population of microbial cells to double in number.

Lag Phase

The interval of time between when a microbial culture is inoculated into medium and when measurable growth begins.

Exponential Phase

The period of rapid cell division during which the population doubles at a constant maximum rate and cells are in their healthiest physiological state.

Stationary Phase

A growth phase where the net growth rate is zero because essential nutrients have been depleted and/or toxic metabolic waste products have accumulated.

Cardinal Temperatures

The minimum, optimum, and maximum temperatures defining the permissive range for growth of a specific organism.

Psychrophiles

Microorganisms with cold temperature growth optima between $0^\circ\text{C}$ and $15^\circ\text{C}$ that inhabit permanently cold natural environments.

Astaxanthin

A pigment produced by the psychrophilic green alga Chlamydomonas that colors snowpacks red, causing "watermelon snow."

Mesophiles

Organisms with midrange temperature optima between $30^\circ\text{C}$ and $40^\circ\text{C}$, commonly found in warm-blooded animals and temperate/tropical environments.

Thermophiles

Organisms with growth temperature optima situated between $40^\circ\text{C}$ and $60^\circ\text{C}$.

Hyperthermophiles

Microorganisms that thrive at extreme temperatures with growth optima greater than $80^\circ\text{C}$, inhabiting hot springs and hydrothermal vents.

Neutrophiles

Organisms that exhibit optimal growth in a near-neutral pH environment between $6$ and $8$.

Acidophiles

Organisms that grow optimally at acidic pH values lower than $6$.

Alkaliphiles

Organisms that grow optimally in high-pH environments with values greater than $9$.

Urease (Helicobacter pylori)

An enzyme produced in high amounts by Helicobacter pylori that hydrolyzes urea into $\text{CO}_2$ and ammonia, binding $\text{H}^+$ to neutralize stomach acid.

Na+/H+ Antiporter

A transport protein utilized by alkaliphiles to export $\text{Na}^+$ while importing $\text{H}^+$ into the cytoplasm, maintaining a near-neutral internal pH.

Halophiles

Organisms that grow best at reduced water potential due to a specific requirement for $\text{NaCl}$.

Extreme Halophiles

Organisms that require high concentrations of salt, typically between $15\%$ and $30\%\,\text{NaCl}$, for survival and growth.

Halotolerant

Organisms that can tolerate reductions in water activity but generally grow best in the absence of added solute, such as Staphylococcus aureus.

Compatible Solutes

Highly water-soluble organic compounds (e.g., glycine betaine, ectoine, sucrose, glycerol) synthesized or concentrated internally to maintain osmotic balance without disturbing metabolism.

Superoxide Dismutase

An antioxidant enzyme that detoxifies harmful superoxide radicals ($\text{O}_2^-$) generated during aerobic metabolism.

Catalase

An enzyme that breaks down toxic hydrogen peroxide ($\text{H}_2\text{O}_2$) into water and oxygen.

Antimicrobial

Any drug, chemical, or substance that kills, inactivates, or retards the growth of microorganisms, including bacteria, viruses, fungi, and parasites.

Antibacterial

A compound or substance that selectively destroys bacterial cells (bactericidal) or halts their multiplication (bacteriostatic).

Bacteriostatic Agent

An antibacterial agent that inhibits bacterial growth and reproduction without causing cell death, maintaining constant viable and total cell counts.

Bacteriocidal Agent

An antibacterial agent that kills bacteria, decreasing viable cell counts while leaving the total physical cell count intact.

Bacteriolytic Agent

An antimicrobial agent that causes the lysis and physical destruction of bacterial cells, resulting in a parallel decline in both viable and total cell counts.

Zone of Inhibition

The clear area around an antibiotic-impregnated paper disc on an agar plate where bacterial growth is prevented due to susceptibility to the diffusing compound.

Minimum Inhibitory Concentration (MIC)

The lowest concentration of an antimicrobial substance needed to completely inhibit visible growth of a specific test microorganism.

$\beta$-Lactamase

A bacterial enzyme that hydrolyzes the four-membered $\beta$-lactam ring of antibiotics such as penicillin, converting them into inactive penicilloic acid.

TetA

A membrane efflux pump protein induced in tetracycline-resistant bacteria that actively exports tetracycline out of the cytoplasm to prevent translation inhibition.

Nucleoside Reverse Transcriptase Inhibitors (NRTIs)

Antiviral nucleoside analogs (e.g., AZT) that terminate viral DNA synthesis by prematurely interrupting the activity of reverse transcriptase.

Nonnucleoside Reverse Transcriptase Inhibitors (NNRTIs)

Antiviral compounds that bind directly to an allosteric pocket of reverse transcriptase to block viral replication.

Echinocandins

Antifungal drugs that target the fungal cell wall by inhibiting $1,3\,\beta\text{-D}$-glucan synthase, frequently used to treat Candida infections.

Polyenes

A class of antifungal agents that bind directly to ergosterol in fungal cytoplasmic membranes, disrupting membrane integrity.

Griseofulvin

An antifungal medication that impairs fungal mitosis by preventing microtubule aggregation.