Microbiology and Cell Biology: Key Concepts and Microorganisms

Microorganisms (Microbes)

Living organisms generally too small to be seen without a microscope, including bacteria, fungi, and viruses

Antonie van Leeuwenhoek

The first person to observe 'animalcules' or 'wee little beasties' in 1675 using a microscope

Fermentation

A process using microbes to convert sugars into alcohol, gases, and organic acids, used for bread, cheese, beer, and wine

Pathogen

A microorganism that causes disease in humans or other animals

Human Microbiome

The community of trillions of microbes and their genes living in association with the human body

Microbiota

The collection of microorganisms in a specific environment, like human skin or the gut, that helps extract nutrients and inhibits pathogens

Phylogenies

Diagrams used to show evolutionary relationships between different organisms

Carl Woese

Scientist who used ribosomal RNA (rRNA) to create a genetics-based tree of life with three domains

Domain Bacteria

Single-celled prokaryotic organisms found in nearly every habitat

Domain Archaea

Unicellular prokaryotes that differ from bacteria in genetics and inhabit extreme environments; none are known human pathogens

Domain Eukarya

The domain containing all organisms with a nucleus, including protists, fungi, plants, and animals

Prokaryotic

Cells that lack a true nucleus and membrane-bound organelles, such as Bacteria and Archaea

Eukaryotic

Cells that contain a true nucleus and membrane-bound organelles, such as algae, protozoa, and fungi

Acellular

Not composed of cells, such as viruses

Virus

An acellular microorganism of protein and genetic material (DNA or RNA) requiring a host cell to multiply

Coccus

Spherical bacterial shape

Bacillus

Rod-shaped bacterial form

Spirillum/Spirochete

Curved or spiral-shaped bacterial form

Golden Age of Microbiology

The period (1857-1914) when Pasteur and Koch discovered connections between microbes and medicine

Carolus Linnaeus

Developed the taxonomic system for categorizing organisms into related groups

Binomial Nomenclature

The system of assigning Latinized scientific names with a genus and species designation

Robert Whittaker

Proposed a five-kingdom tree including Animalia, Plantae, Protista, Fungi, and Monera

Bergey's Manuals

The standard references for identifying and classifying bacteria

Algae

Plant-like eukaryotes that can be unicellular or multicellular and derive energy via photosynthesis

Protozoa

Unicellular eukaryotes with complex structures; most are motile

Helminths

Multicellular parasitic worms studied in microbiology because their eggs and larvae are often microscopic

Wavelength

The distance between one peak of a wave and the next peak

Reflection

When light bounces off a surface and stays in the same medium

Refraction

When light bends as it passes from one medium to another, changing speed and direction

Magnification

The ability of a lens to enlarge the image of an object

Resolution

The ability to distinguish two separate points; increased by shortening wavelength or increasing numerical aperture

Absorbance

The amount of light absorbed by a substance

Transmittance

The fraction of light passing through a substance

Bright-field Microscopy

Uses white light for basic visualization and relies on light absorption for contrast

Fluorescence Microscopy

Uses specific wavelengths to excite fluorophores to highlight specific structures with high contrast

Electron Microscopy

Uses magnets to focus electrons, producing much greater magnification than light microscopy

TEM (Transmission Electron Microscope)

Requires thin sections to see internal cell details

SEM (Scanning Electron Microscope)

Requires sputter-coating to see 3D surface details

Robert Hooke

The first person to describe what we now call cells

Staining and Fixation

Process used to stick microbes to a slide and immobilize them for viewing

Protons, Neutrons, Electrons

Positive particles, neutral particles, and tiny negative particles orbiting the nucleus

Octet Rule

The chemical principle of having 8 electrons around an element in a Lewis Structure

pH Scale (Acids vs Bases)

Acids (0-7) release H+; Bases (7-14) accept H+; Neutral is pH 7

Covalent Bond

A strong bond involving the sharing of electrons, described as a chain link

Ionic Bond

A bond involving the transfer of electrons, described as being like a magnet

Hydrogen Bond

A weak attraction between polar molecules, broken by heat and described as a hook and loop system

CHONPS

Acronym for the six essential elements of life: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur

Functional Group

Specific clusters of atoms (like -OH or -NH2) that determine a molecule's chemical behavior

Monomers and Polymers

Single molecular 'bricks' and the long chains they form when linked together

Dehydration Synthesis

Chemical reaction that joins molecules together by removing a water molecule

Hydrolysis

The chemical process of breaking polymers into monomers by adding water

Glucose

The most important monosaccharide (C6H12O6) and primary energy source for most microbes

Starch, Glycogen, Cellulose

Glucose polymers used for energy storage in plants, animals/bacteria, and structure in plants, respectively

Lipids

Nonpolar organic compounds insoluble in water; the main component of cell membranes

Triglyceride

Main component of body fat used for energy storage

Phospholipid

Amphipathic molecule with a polar (hydrophilic) head and nonpolar (hydrophobic) tails; forms the bilayer

Sterols

The most common type of steroids, which contain an -OH group

Amino Acids

The 20 individual monomers that serve as the building blocks of proteins

Peptide Bond

The covalent chemical bond that links amino acids together

Primary Protein Structure

The specific linear sequence of amino acids in a polypeptide chain

Secondary Protein Structure

Coils and folds like Alpha-helices and Beta-pleated sheets created by hydrogen bonds

Tertiary Protein Structure

The overall 3D shape of a single polypeptide chain

Quaternary Protein Structure

Structure formed when two or more polypeptide chains join to form a functional protein

Denaturation

Process where a protein loses its shape and function due to heat or pH changes

Enzymes

Specialized proteins that act as biological catalysts to speed up reactions

Nucleotide

The monomer of nucleic acids consisting of a sugar, a phosphate, and a nitrogenous base

Phosphodiester Bond

Strong covalent bond linking the sugar-phosphate backbone of DNA/RNA

DNA vs RNA

DNA uses deoxyribose and Thymine (A-T); RNA uses ribose and Uracil (A-U)

Metabolism

All chemical and physical processes within a cell to maintain life

Genome

The complete set of genetic material composed of DNA

Peptidoglycan

Primary structural molecule in bacterial cell walls that prevents rupturing from osmotic pressure

Fluid Mosaic Model

Description of the cell membrane as a flexible layer of lipids with moving proteins

Endospores

Highly resistant, dormant structures for surviving extreme heat or chemicals

Sporulation vs Germination

Sporulation is the transition from active to dormant; Germination is the return to an active state

Chemotaxis

The movement of a bacterium in response to chemical gradients

Endosymbiotic Theory

Explains the evolution of eukaryotes by a large cell engulfing smaller bacteria that became organelles

Mitochondria

Organelle evolved from aerobic bacteria; the site of ATP production with its own DNA and 70S ribosomes

Chloroplast

Organelle evolved from photosynthetic bacteria; converts sunlight into chemical energy

Cytoskeleton

Network of microfilaments and microtubules providing structural support and acting as a transport highway

80S Ribosomes

Large ribosomes used for protein synthesis in eukaryotic cells

Pseudopodia

Literally 'false feet'; cytoplasmic extensions used for movement and capturing food

Phagocytosis

Type of endocytosis known as 'cell eating' where the cell engulfs large particles

Exocytosis

Process of expelling waste or secretions by fusing a vesicle with the cell membrane

Ubiquitous

Term meaning microorganisms are found in every habitable environment on Earth

Resident vs Transient Microbiota

Resident microbes live on/in us constantly; transients are only there temporarily

Fungi

Heterotrophic eukaryotes with cell walls typically made of chitin

Mold vs Yeast

Molds are multicellular filaments (hyphae); yeasts are unicellular and reproduce by budding

Dimorphism

Ability of fungi to switch between mold-like (environment) and yeast-like (host) forms

Mycoses

Diseases caused by fungi

Lichen

Symbiotic association between a fungus and a photosynthetic partner like an alga