Microbiology Overview - Domains, Genetics, Metabolism, and Immunology

Comprehensive vocabulary flashcards covering the history of microbiology, cellular organization, genetics, stains, microscopy, microbial metabolism, fungi, and immunology.

Microbiology

The study of living creatures too small to see with the naked eye, including bacteria, fungi, protozoa, algae, viruses, and other minute organisms.

Ignaz Sammelweis

A Viennese physician who, in $1840$, identified a correlation between putrefaction in autopsies and puerperal fever in maternity wards and advocated handwashing between patients.

Louis Pasteur

A French scientist who demonstrated in $1850$ that microorganisms ferment sugar into alcohol and cultured Bacillus anthracis to prove it was the causative agent of anthrax.

Joseph Lister

An English surgeon who in $1860$ introduced carbolic acid (phenol) to dress wounds and spray operating rooms to eliminate what he termed "septic germs."

Robert Koch

A German physician who established in $1890$ that anthrax bacteria are consistently present in infected blood, transmit the disease, and can be isolated outside the host.

Lac Operon Model

A model of the genetic control of enzyme synthesis discovered and described in $1960$ by Francois Jacob and Jacques Monod.

Polymerase Chain Reaction (PCR)

A laboratory technique invented in $1985$ by Kary Mullis used to amplify any targeted DNA sequence.

Prions

Infectious proteins whose discovery and characterization earned Stanley Pruisher the Nobel Prize in $1997$.

Three-Domain System

A biological classification system dividing all known organisms into three primary domains: Bacteria, Archaea, and Eukarya.

Cell Theory

A fundamental biological theory established in the $1800\text{s}$ stating: 1) all living things consist of one or more cells; 2) the cell is the basic unit of life; and 3) all cells arise from pre-existing cells.

Koch's Postulates

Four criteria used to establish that a microorganism causes disease: 1) identical microbe present in all disease cases; 2) isolated and grown in pure culture; 3) causes disease in a healthy, susceptible host; 4) reisolated from the inoculated host.

Site-Directed Mutagenesis

A targeted genetic engineering technique used to change an area of genetic material as small as a single amino acid without modifying other characteristics.

Cloning (Microbial)

The isolation and amplification of individual genes using plasmid vectors to transfer a gene from a complex genome into a simpler host for sequence analysis or functional study.

In Vitro Recombination

The process of cleaving isolated DNA with restriction endonucleases and joining it to a plasmid vector using DNA ligase, followed by transfection into a host cell.

Degenerative Nature of the Genetic Code

The redundancy of the genetic code where multiple triplet codons specify the same amino acid, typically requiring consistency only in the first two nucleotide bases.

Conjugation

The transfer of genetic material between bacterial cells via direct contact through a sex pilus encoded by the tra gene on plasmids, occurring from $F^+$ or $Hfr$ donors to $F^-$ recipients.

Transformation

A passive, diffusion-type process where competent bacterial cells directly acquire naked exogenous DNA or RNA from living, dying, or dead cells.

Transfection

The transfer of genetic material into cells mediated specifically by viral agents, such as T-even bacteriophages infecting bacteria.

Transduction

The process by which bacteriophages transfer bacterial genetic material into a host cell through either a lytic (virulent) or lysogenic (temperate) cycle.

Acid-Fast Stain

A differential staining procedure where mycobacteria resist acid-alcohol decolorization and retain red carbolfuchsin, while non-acid-fast organisms take up a methylene blue counterstain.

Gram Stain

A four-step differential staining technique using crystal violet, iodine, alcohol, and safranin red that differentiates purple-blue Gram-positive bacteria from red Gram-negative bacteria.

Dark-Field Microscope

A microscope that employs a specialized condenser producing a hollow cone of light, allowing minute or thin specimens to appear bright white against a completely dark background.

Phase-Contrast Microscope

An optical microscope that exploits variations in refractive index to visualize small, dense internal organelles in living specimens without requiring staining.

Transmission Electron Microscopy (TEM)

An electron microscopy technique achieving resolution greater than $1\,\text{nm}$ to examine internal organelles and macromolecules in ultrathin specimen sections ($\le 0.1\,\text{nm}$) under a vacuum.

Scanning Electron Microscopy (SEM)

An electron microscopy technique that utilizes a focused beam of electrons to scan and visualize the three-dimensional surface architecture of a specimen.

Photoautotroph

An organism that captures light energy to convert carbon dioxide ($CO_2$) and water ($H_2O$) into organic carbon compounds, exemplified by green algae.

Photoheterotroph

An organism that harnesses light energy while utilizing preformed organic carbon compounds as its carbon source, such as purple or green non-sulfur bacteria.

Chemoautotroph

An organism that obtains energy by oxidizing inorganic compounds such as hydrogen sulfide ($H_2S$), ammonia ($NH_3$), or iron to fix carbon dioxide ($CO_2$) into organic matter.

Chemoheterotroph

An organism that relies on organic molecules to supply both its metabolic energy and structural carbon, encompassing saprobes feeding on dead matter and parasites utilizing host fluids.

Psychrophiles

Cold-tolerant bacteria, such as Listeria, capable of active growth and survival at low temperatures that typically inhibit other bacterial species.

Extreme Halophiles

Organisms that thrive in hyper-saline environments (up to $20\%$ salinity), utilizing membrane-bound bacteriorhodopsin to pump $H^+$ ions using light, which imparts a pink color.

Thermoacidophiles

Extremophilic microorganisms found in geysers and hot springs that thrive at temperatures up to $80^\circ\text{C}$ and acidic conditions between $\text{pH } 1$ and $\text{pH } 4$.

Methanogens

Obligate anaerobic microorganisms that reduce carbon dioxide ($CO_2$) to methane ($CH_4$) in the presence of hydrogen, common in swamps and ruminant digestive tracts.

Endospores

Thick-walled, dehydrated dormant structures produced by genera such as Clostridium to endure extreme environmental conditions including desiccation, freezing, and heat.

Penicillium roqueforti

A widespread fungal species isolated from soil and plant matter that has been utilized in the production of blue cheeses and flavoring agents since approximately $50\,\text{AD}$.

Blastospores

Asexual fungal spores produced by yeast cells via budding, where the cell surface protrudes, enlarges, and pinches off from the mother cell.

Chlamydospores

Thick-walled asexual resting spores formed when vegetative hyphal segments swell in aging or drying fungal cultures.

Arthrospores

Thick-walled, barrel-shaped asexual spores that form directly via the fragmentation of vegetative fungal hyphae.

Conidiospores

Unenclosed asexual fungal spores formed externally at the tips of specialized stalk structures termed conidiophores.

Sporangiospores

Asexual fungal reproductive spores that develop within an enclosed, sac-like organ called a sporangium.

Basidiospores

Sexual fungal spores characteristic of Basidiomycetes that develop externally attached to the tips of club-shaped microscopic structures called basidia.

Ascospores

Sexual spores characteristic of Ascomycetes produced within a specialized microscopic sac termed an ascus, usually enclosed inside an ascocarp.

Zygospores

Large, thick-walled diploid sexual resting spores formed through the fusion of two compatible ($+\text{ and } -$) hyphal mating types in zygomycetes.

Oospores

Sexual fungal spores that result from the fertilization of a female oogonium by a male antheridium during vegetative life cycles.

B Cells (B Lymphocytes)

Adaptive immune cells that differentiate into plasma cells to synthesize and secrete specific antibodies ($\text{IgG}$, $\text{IgA}$, $\text{IgD}$, $\text{IgE}$, and $\text{IgM}$) and provide immunological memory.

T Cells (T Lymphocytes)

Adaptive immune cells that eliminate virus-infected cells and mediate cellular immune responses against pathogens (such as fungi) that bypass innate barriers without requiring antibodies.

Null Cells

Immune lymphocytes characterized by large cytoplasmic granules that assist both innate and adaptive (B and T) cells to mediate host defense.

Innate Immunity

The rapid, non-specific branch of the immune system composed of physical/chemical barriers, commensal microorganisms, protective leukocytes, and soluble serum factors.

Multipotential Hematopoietic Stem Cell

A pluripotent bone marrow precursor cell (hemocytoblast) that gives rise to both the common myeloid progenitor and common lymphoid progenitor lineages.