Microbial Growth, Nutrition, and Cell Structure

Comprehensive vocabulary flashcards covering bacterial growth dynamics, physical growth requirements, culture media, endospores, domain diversity, and prokaryotic cellular structures.

Binary Fission

An asexual reproductive process in most bacteria where a cell doubles in mass, replicates its DNA, and synthesizes a septum to divide into $2$ genetically identical cells.

Generation Time

The interval of time between successive binary fissions, also referred to as doubling time.

Lag Phase

The first phase of a bacterial growth curve during which no cell division occurs while bacteria adapt to their new environment.

Logarithmic (Log) Phase

The phase of exponential population growth in a bacterial growth curve during which human disease symptoms usually develop.

Stationary Phase

The phase in a bacterial growth curve where reproductive and death rates equalize, maintaining a stable population size.

Decline Phase

The final phase of a bacterial growth curve, also known as the exponential death phase, caused by waste accumulation and nutrient scarcity.

Bacterial Growth Curve

A graphical representation illustrating the population dynamics of bacterial growth across $4$ distinct phases: lag, log, stationary, and decline.

Endospore

A highly resistant, dormant structure produced by species of Bacillus and Clostridium in response to severe nutrient limitation.

Dipicolinic Acid

An organic compound present in the endospore core that complexes with $\text{Ca}^{2+}$ to stabilize proteins and DNA, helping to dehydrate the spore.

Psychrophiles

Microorganisms that grow optimally at cold temperatures below $15\,^\circ\text{C}$ and constitute the largest portion of prokaryotes on Earth.

Mesophiles

Microorganisms that thrive in medium temperature ranges of $10\,^\circ\text{C}$ to $45\,^\circ\text{C}$ with an optimum near $37\,^\circ\text{C}$, including human pathogens.

Thermophiles

Organisms that multiply best at hot temperatures around $60\,^\circ\text{C}$, commonly found in compost heaps and hot springs.

Hyperthermophiles

Archaea that grow optimally at extreme temperatures above $80\,^\circ\text{C}$ (optima near $95\,^\circ\text{C}$), such as those found in seafloor hydrothermal vents.

Obligate Aerobes

Prokaryotes that strictly require oxygen ($\text{O}_2$) for cellular respiration and growth.

Obligate Anaerobes

Prokaryotes that cannot use oxygen ($\text{O}_2$) and are inhibited or killed by its presence.

Aerotolerant Anaerobes

Microorganisms that do not utilize oxygen ($\text{O}_2$) for growth but are insensitive to its presence.

Facultative Prokaryotes

Organisms capable of growing either in the presence of oxygen ($\text{O}_2$) or in reduced oxygen environments.

Capnophilic Bacteria

Bacteria that require a low-oxygen atmosphere enriched with high levels of carbon dioxide ($\text{CO}_2$).

Thioglycollate Broth

A specialized liquid growth medium used in testing an organism's oxygen sensitivity and oxygen requirement pattern.

Acidophiles

Acid-tolerant prokaryotes that grow optimally at pH levels below $6.0$.

Barophiles

Organisms capable of surviving under extremely high hydrostatic pressures, such as psychrophiles living in the deep ocean floor.

Halophiles

Prokaryotes requiring or tolerating high concentrations of sodium chloride ($\text{NaCl}$) for growth.

Complex Medium

A culture medium containing chemically unidentified components, such as peptone and beef extract, where the exact chemical composition is unknown.

Synthetic Medium

A chemically defined culture medium in which every constituent and its exact quantitative concentration is known.

Selective Medium

A culture medium containing specific agents that inhibit the growth of unwanted microbes while encouraging the growth of desired species.

Differential Medium

A culture medium containing specific chemical indicators to visually differentiate organisms based on their metabolic or biochemical properties.

Streak-Plate Isolation Method

A laboratory technique used to spread bacterial cells across an agar surface to obtain isolated pure colonies.

Proteobacteria

The largest and most diverse bacterial phylum, encompassing species such as Escherichia coli and numerous human pathogens.

Firmicutes

A bacterial phylum consisting primarily of Gram-positive organisms, including the genera Bacillus, Clostridium, Staphylococcus, and Streptococcus.

Actinobacteria

A phylum of Gram-positive bacteria that includes Streptomyces, a genus known for producing the antibiotic streptomycin.

Cyanobacteria

Photosynthetic bacteria that utilize chlorophyll to produce oxygen, historically responsible for oxygenating Earth's atmosphere.

Chlamydiae

A phylum of extremely small, obligate intracellular, mostly pathogenic bacteria.

Euryarchaeota

A major archaeal phylum comprising methanogens, extreme halophiles, and thermoacidophiles.

Crenarchaeota

A phylum of Archaea that primarily inhabit hot, acidic extreme environments like hot springs and geothermal volcanic vents.

Cocci

Spherical-shaped bacterial cells that can exist as single units, pairs (diplococci), chains (streptococci), clusters (staphylococci), tetrads, or sarcinae.

Bacilli

Rod-shaped bacterial cells that may form chains or produce endospores.

Bacteria Shapes

The primary morphological classifications of bacterial cells, categorized as spheres (cocci), rods (bacilli), and spirals (vibrios, spirilla, spirochaetes).

Fimbriae

Thin, hair-like protein fibers (pilin with adhesins) extending from the bacterial surface that facilitate attachment to host tissues and surfaces.

Conjugation Pili

Specialized protein appendages (sex pili) that connect bacterial cells to enable the transfer of plasmids, genetic material, and antibiotic resistance genes.

Flagella

Long, helical protein structures composed of flagellin, a hook, and a rotating basal body that propel bacteria through fluid environments.

Endoflagella

Internal flagella located within the periplasmic space between the peptidoglycan and outer membrane of spirochetes, producing twisting motility.

Glycocalyx

An outer polysaccharide coating external to the cell wall that functions as a virulence factor by resisting phagocytosis, enabling adhesion, and preventing desiccation.

Capsule

A thick, organized, and tightly bound layer of glycocalyx surrounding a bacterial cell.

Slime Layer

A loose, unorganized, and diffuse layer of glycocalyx polysaccharides surrounding a bacterial cell.

Peptidoglycan

A rigid mesh-like polymer of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by tetrapeptides, forming the structural backbone of bacterial cell walls.

Teichoic Acid

An acidic polysaccharide present in the thick ($16\text{--}80\,\text{nm}$) peptidoglycan cell walls of Gram-positive bacteria, absent in Gram-negative bacteria.

Lipopolysaccharide (LPS)

A complex glycolipid in the outer membrane of Gram-negative bacteria containing Lipid A, which acts as an endotoxin upon cell lysis.

Mycoplasma

A unique bacterial genus characterized by the complete absence of a cell wall.

Plasma Membrane

A selectively permeable lipid bilayer containing integral and peripheral proteins that acts as a physical barrier and mediates movement, attachment, communication, and metabolic reactions.

Inclusion Bodies

Cytoplasmic storage deposits in bacteria containing nutrient reserves such as glycogen, sulfur, lipids, metachromatic granules (polyphosphates), or magnetosomes (magnetite).

Nucleoid

The membrane-less cytoplasmic region of a prokaryotic cell that harbors the essential circular chromosome.

Plasmid

A small, extrachromosomal circular DNA molecule carrying nonessential genetic information, such as antibiotic resistance or toxin production genes.