General Microbiology: Microscopy, Cell Structure, Function, and History

Comprehensive vocabulary flashcards covering microscopy principles, bacterial morphology and ultrastructure, eukaryotic cell organelles, microbial ecology, biotechnology, and the historical milestones of microbiology.

Resolution

The ability of a lens to separate or distinguish between small objects that are close together.

Total Magnification

The overall visual enlargement of a specimen, calculated by multiplying the magnifying power of the objective lens by that of the eyepiece lens ($\text{Total Magnification} = \text{Objective} \times \text{Eyepiece}$).

Refraction

The bending of light rays as they pass from one transparent medium to another of different density (for example, from air into glass).

Immersion Oil

A colourless liquid that possesses the same refractive index ($n$) as glass; it eliminates air between the slide and objective lens so light rays enter without being refracted and lost, thereby increasing numerical aperture and resolution.

Fixation

The process by which internal and external structures of cells and microorganisms are preserved and fixed in position, achieved either physically (passing a slide through a Bunsen burner flame) or chemically (adding chemical reagents/stains).

Chromophore

A chemical group within a biological dye molecule that imparts its characteristic colour and allows binding to cellular components via ionic, covalent, or hydrophobic bonds.

Differential Stain

A staining procedure that utilizes a primary stain and a counterstain to distinguish between different types of cells or cellular structures (such as Gram stain, acid-fast stain, and endospore stain).

Selective (Special) Staining

A staining method formulated specifically to emphasize and reveal specific bacterial structures not visible through conventional methods, such as bacterial capsules or flagella.

Transmission Electron Microscope (TEM)

An electron microscope in which a beam of electrons passes directly through ultra-thin sections of a specimen and is focused by magnetic lenses onto a fluorescent screen, allowing observation of internal ultra-structure.

Scanning Electron Microscope (SEM)

An electron microscope in which primary (1^\\text{o}) electrons scan across the specimen surface, knocking off secondary (2^\\text{o}) electrons that are collected and amplified to form a detailed image of outer surface structures and topography.

Endosymbiotic Theory

The evolutionary theory stating that eukaryotic organelles originated when an ancestral anaerobic prokaryote engulfed an aerobic bacterium (which evolved into the mitochondrion) and a photosynthetic cyanobacterium (which evolved into the chloroplast).

Mutualism

A symbiotic relationship between two different organisms where both partner species derive biological benefit ($+ / +$).

Commensalism

A symbiotic relationship between two organisms where one organism benefits while the other is neither helped nor harmed ($+ / 0$).

Parasitism

A symbiotic relationship wherein one organism (the parasite) benefits by feeding on or living inside a living host organism, causing harm to the host ($+ / -$).

Lichens

Composite organisms resulting from a mutualistic symbiotic relationship between fungi and photosynthetic algae or cyanobacteria; they grow on rocks and secrete organic acids that biologically weather rock into inorganic soil.

Saprotroph

A decomposer microorganism that feeds upon non-living organic matter and dead organisms, releasing extracellular enzymes to recycle minerals and essential nutrients back into the ecosystem.

Bioremediation

The practical application of microorganisms to remove, degrade, or neutralize toxic environmental pollutants from contaminated soil, water, or industrial sites.

Biodeterioration

The unwanted microbial decomposition and economic spoilage of inanimate structural and material goods, including building foundations, stone, timber, and furniture.

Probiotics

Live, beneficial bacteria and yeasts (such as $L.\text{ acidophilus}$, $L.\text{ casei}$, and $B.\text{ bifidum}$) that support digestion, improve human gut microflora, and suppress harmful pathogens.

Cytoskeleton

An intracellular network of interconnected protein filaments (composed of microfilaments, microtubules, and intermediate filaments) that provides mechanical support, maintains eukaryotic cell shape, and facilitates cell motility.

Pseudopodium

A temporary cellular extension of the plasma membrane ('false foot') driven by actin microfilaments, utilized for amoeboid locomotion and the engulfment of food particles via phagocytosis.

Phagocytosis

A form of endocytosis by which a eukaryotic cell surrounds, engulfs, and digests solid extracellular particles or foreign microorganisms using a membrane-bound phagosome that fuses with a lysosome.

Pinocytosis

A type of endocytosis commonly referred to as 'cell drinking', during which small invaginations of the plasma membrane internalize droplets of extracellular fluid containing dissolved nutrients.

Coccus

A bacterium possessing a spherical or round morphological shape (plural: cocci).

Bacillus

A bacterium possessing a rod-like morphological shape (plural: bacilli).

Pleomorphic

Bacteria that exhibit variable cell shapes and lack a single, uniform characteristic morphological form.

Arrangements of Cocci

Specific cellular grouping patterns resulting from planes of cell division, including pairs (diplococci), chains (streptococci), flat packets of four (tetrad), cubical packets of eight (sarcina), and irregular grape-like clusters (staphylococci).

Pilus

A hair-like protein appendage extending from the bacterial surface; specialized conjugation pili (sex pili) transfer genetic material directly from a donor bacterium to a recipient cell.

Peptidoglycan

A complex polymer forming the rigid bacterial cell wall, composed of alternating repeating subunits of two amino sugars ($N\text{-acetylglucosamine}$ and $N\text{-acetylmuramic acid}$) cross-linked by a chain of amino acids.

Gram-Positive Cell Wall

A bacterial cell envelope characterized by a thick, multi-layered peptidoglycan meshwork embedded with teichoic acid and lipoteichoic acid, situated above a single plasma membrane, which retains crystal violet dye to stain purple.

Gram-Negative Cell Wall

A complex bacterial envelope consisting of a thin peptidoglycan layer enclosed within a wide periplasmic space and covered by an asymmetric outer membrane rich in lipopolysaccharide (LPS), phospholipids, and porins, which stains red with safranin.

Lipopolysaccharide (LPS)

A large glycolipid located in the outer leaflet of Gram-negative outer membranes; its Lipid A component acts as a toxic endotoxin during severe bacterial infections.

Chemotaxis

The directed movement of a motile bacterium toward chemical attractants (such as nutrients) or away from chemical repellents, mediated by membrane-bound chemoreceptors.

Actinomycetes

A group of Gram-positive, spore-forming, filamentous bacteria (such as $Streptomyces\text{ sp.}$) that resemble fungal mycelia and produce valuable antibiotics like streptomycin.

Gas Vacuole

An internal protein-walled prokaryotic inclusion that traps gas to provide cellular buoyancy for floating at optimal depths in aquatic environments.

Endospore

An extremely resistant, dormant survival structure formed inside certain bacterial genera (e.g., $Bacillus$, $Clostridium$) that can withstand extreme heat, radiation, desiccation, and chemical disinfectants.

Osmosis

The net diffusion of water molecules across a selectively permeable membrane from an area of higher water concentration (dilute solution) toward an area of lower water concentration (concentrated solute solution).

Cell Theory

The unifying biological principle, first outlined by Robert Hooke in $1665$, stating that all living organisms are composed of individual structural units called cells.

Spontaneous Generation

The early historical hypothesis, defended by Aristotle and John Needham, asserting that living organisms could develop and arise spontaneously from non-living matter.

Biogenesis

The fundamental biological theory, formalized by Rudolf Virchow ($1858$) and proven experimentally by Louis Pasteur, stating that living cells can arise only from preexisting living cells.

Redi's Experiment

A series of controlled tests performed in $1668$ using decaying meat in unsealed, cork-sealed, and gauze-covered flasks, proving that maggots develop on meat only from fly eggs and do not generate spontaneously.

Pasteur's Swan-Neck Flask Experiment

The landmark $1861$ experiment in which boiled nutrient broths kept in flasks with open, S-shaped curves remained indefinitely sterile because airborne dust settled in the neck bend, definitively disproving spontaneous generation.

Pasteurization

A controlled, mild heat treatment developed by Louis Pasteur (heating liquids at $55\text{-}60^\circ\text{C}$ below boiling) that kills pathogenic and spoilage microorganisms in beverages without destroying their flavor.

Aseptic Technique

A set of preventative laboratory and clinical procedures, pioneered by Pasteur and Tyndall, designed to prevent the contamination of cultures, wounds, and sterile media by unwanted microorganisms.

Koch's Postulates

A definitive four-step experimental framework established by Robert Koch ($1876$) to prove that a specific microorganism is the causative agent of a specific transmissible infectious disease.

Antibiotic

A chemical substance produced naturally by microorganisms (or synthesized artificially) that selectively kills or inhibits the physiological growth of other microorganisms.

Vaccine

An immunogenic biological preparation consisting of killed microbes, live attenuated strains, or inactivated toxins administered to induce an adaptive immune response and protect an individual from subsequent pathogen exposure.

Antitoxin

A specific protective antibody produced by the immune system that binds to and neutralizes a specific soluble bacterial toxin.

Agar

A sulfated polysaccharide isolated from red algae, suggested by Fannie Hesse as an ideal solidifying culture medium agent because it remains solid above $30^\circ\text{C}$, melts above $100^\circ\text{C}$, and is not digested by most bacteria.