BIOS 250 - Unit 1: Microbial Growth and Characterization

Microbiology

The branch of science that deals with microorganisms/microbes

Microbes

Organisms typically seen with a microscope

Spontaneous generation

The theory that life can arise from nonliving matter if the material contained pneuma

Pneuma

Vital heat that gives life

Miasma theory

The theory that diseases are caused by inhaling “bad air” or foul-smelling vapors from decaying matter

Germ theory of disease

The theory that diseases may result from microbial infection

Louis Pasteur

• Challenged and disproved spontaneous generation with swan neck flask experiment

• Established germ theory of disease

John Snow

• Ran the first epidemiological study based on London cholera outbreaks

• Tracked outbreaks to water contaminated by sewage

• Helped refute miasma theory

Ignaz Semmelweis

• Suggested handwashing with chlorinated lime water

• Resulted in dropped mortality rates in healthcare facilities to 1%

Joseph Lister

• Via Semmelweis and Pasteur demanded handwashing/cleanliness

• Started using carbolic acid (phenol) antiseptic during surgery

• Reduced patient deaths by two-thirds

Florence Nightingale

• Founder and mother of modern nursing

• First to implement strict sanitation in hospitals (clean water, ventilation, handwashing, bedding, proper diets, etc.)

• First to recognize impact of diseases on warfare

• First female member of Royal Statistical Society in England

Robert Koch

Showed that one microbe caused one disease

Endosymbiotic theory

The theory that mitochondria and chloroplasts arose as a result of prokaryotic cells establishing a symbiotic relationship within a eukaryotic host

Scientific method

Observation/question, research topic area, hypothesis, test with experiment, analyze data, report conclusions (endless cycle)

Prokaryote

• Unicellular

• Simple structure (plasma membrane, genetic material in nucleoid region)

• Lacks membrane-bound organelles

• Single, circular DNA molecule in nucleoid

• Replicates via binary fission (asexual)

• Diverse metabolic pathways (aerobic, anaerobic, photosynthetic)

• Energy produced in cell membrane

• Growth involves increase in cell size and number

• 1-5 μm

Eukaryote

• Unicellular or multicellular

• Complex structure (nucleus, membrane-bound organelles)

• Multiple linear chromosomes within a nucleus

• Replicate via mitosis and meiosis (asexual and sexual)

• Metabolism includes cellular respiration and photosynthesis

• Energy produced in mitochondria or chloroplasts

• Growth involves cell division and differentiation

• 5-100 μm

Viruses

• Acellular

• Very simple (consists of only genetic material encased in a protein coat)

• DNA or RNA but not both

• Replicates inside the host cell using the host’s machinery to produce more viral particles

• No metabolism, relies on host cell for energy

• No growth

• 0.05-0.1 μm

Taxonomy

The classification, description, identification, and naming of living organisms

Binomial nomenclature

• A two-word naming system for identifying organisms by genus and specific epithet

• Used for prokaryotes and eukaryotes

Microscopy

Technique used to visualize objects too small to see with the naked eye

Light/optical microscope

Use light to visualize images

Simple microscope

Light passes through 1 lens

Compound microscope

Light passes through 2 lenses

Magnification

The ability of a lens to enlarge the image of an object when compared to the real object

Ocular lenses

• Eyepiece

• Magnifies images 10 times

• Look through to view organism

Objective lens

• Located near specimen

• Typically come in different magnifications ranging from 4x to 100x

Stage

Where the specimen is placed

Coarse adjustment

Used for large-scale movements with 4x and 10x objective lenses

Fine adjustment

Used for small-scale movements especially with 40x or 100x objective lenses

Condenser

Focuses all of the light rays on the specimen to maximize illumination

Light

• Illuminates specimen

• Goes through condenser

Carrying handle

Used to carry microscope properly

Equation of magnificaton

Objective lens x Ocular lens (typically 10x)

Specimen staining

Technique used to increase the visibility of microbes that are very translucent and hard to see under the microscope, preserve sample morphology, and highlight morphological features

Simple staining

• A single dye is used to highlight cell shape and structure

• Useful for simple visualization, but cannot study organism further

• Uses basic dyes (crystal violet, methylene blue, safranin)

Differential staining

Uses multiple dyes to differentiate between microbes

Fluorescence microscopy

Uses an ultraviolet light source to excite fluorophores within a specimen

Fluorophores

• Chemical compounds that absorb/emit light when excited by specific wavelengths of light energy

• Can be used to view specific molecules and highlight specific structures in living cells

Electron microscopy

• Uses electrons instead of visible light (more powerful than light beams, shorter wavelength = greater resolution)

• Useful for visualization of viruses and small cell structures

Transmission electron microscope (TEM)

Electron beams pass through specimen to create detailed images of internal structure (2-D)

Scanning electron microscope (SEM)

Scans surface of specimen with electron beam to create 3-D image that provides information on surface topography

Brightfield microscope

A compound microscope with two or more lenses that produce a dark image on a bright background

Coccus

Round

Diplococci

Pair of two cocci

Tetrad

Grouping of four cells arranged in a square

Streptococci

Chain of cocci

Staphylococci

Cluster of cocci

Bacillus

Rod

Diplobacilli

Pair of two bacilli

Streptobacilli

Chain of bacilli

Spirillum

Spiral

Cytoplasm

A gel-like substance composed of water and dissolved chemicals needed for growth

Capsule

• An organized layer located outside the cell wall and usually composed of polysaccharides or proteins

• Protects the cell, adheres to surfaces, and evades immune cells (slippery)

Plasma membrane

• Phospholipid bilayer

• Protective layer with selective permeability

• Contains glycolipids and glycoproteins (provide structural support, detection/release of signals, secretion of virulence factors, and ion transport)

Fluid mosaic model

The ability of membrane components to move fluidly within the plane of the membrane

Cell wall

• Made of peptidoglycan

• Gives shape and rigidity to cell

• Protects the cell membrane

Gram-positive bacteria

• Thick peptidoglycan layer

• Threaded by negatively charged teichoic acids

• Retain crystal violet dye in gram stain

Gram-negative bacteria

• Thin peptidoglycan layer

• Bi-layer outer membrane with lipopolysaccharide (LPS)

• Stained pink in gram stain

Mycolic acids

• Fatty acids

• Waxy outer membrane protects against toxic substances

Acid fast stain

Used to identify mycolic acid-containing pathogens

Pili

• Longer, less numerous protein appendages that aid in attachment to surfaces

• Used in DNA transfer (conjugation)

Fimbriae

• Short bristle-like proteins projecting from the cell surface by the hundreds

• Attaches to surfaces or host tissues

• Motility

Nucleoid

• Region where DNA (singular circular double-stranded) is organized

• Genetic control center of the cell

• Not membrane-bound

Plasmids

• Extrachromosomal DNA (small, circular, double-stranded DNA molecules)

• Carries genes for antibiotic resistance and toxins

• Pili transfer

• Impacts antibiotic control in healthcare

Ribosomes

• Sites of protein synthesis

• Translates mRNA to protein

Prokaryotic ribosome

30S small subunit, 50S large subunit, 70S complete ribosome

Endospores

• Formed by vegetative cells (gram-positive) typically when conditions are unfavorable

• Resistant to extreme temperatures and radiation

• Does not absorb gram stain

• Dehydrated

• No metabolic activity

• Dormant

• No growth

Flagella

• Used by cells to move in aqueous environments

• Long whip-like structure

• Composed of filament, hook, and basal body

Phototaxis

Bacteria moving in response to light

Chemotaxis

• Bacteria moving in response to chemical gradients

• Flagellar rotates counterclockwise towards nutrients

• Flagellar rotates clockwise (freezes and tumbles in place) away from toxins

Hopanoids

Multiringed structures that strengthen bacterial membranes

Cholesterol

• For eukaryotes

• Add fluidity and stability to membrane

Endocytosis

The uptake of matter through plasma membrane invagination and vacuole/vesicle formation

Phagocytosis

Cell eating

Pinocytosis

Cell drinking

Receptor-mediated endocytosis

A type of endocytosis that is initiated by specific molecules called ligands when they bind to cell surface receptors on the membrane

Exocytosis

The process by which secretory vesicles (spherical membranous sacs) release their contents to the cell’s exterior

Chitin

Cell wall for fungi

Cellulose

Cell wall for plants

Silica

Cell wall for algae

Giemsa stain

Histological stain used for blood samples from patients

Cilia

• Found in some eukaryotic cells

• Shorter than flagella and often cover the entire surface of a cell, but are structurally similar to flagella

• Whip-like motion powered by ATP

Cytoskeleton

• Very critical in eukaryotes

• Provides structural support, anchors organelles, and provides a network of roads for transportation of cargo and vesicles

• Made of microfilaments, intermediate filaments, and microtubules

Microfilaments

• Composed of two intertwined strands of actin each composed of actin monomers

• Work together with motor proteins to effect muscle contraction in animals or the amoeboid movement of some eukaryotic microbes

• Endocytosis and exocytosis

Intermediate filaments

• A diverse group of cytoskeletal filaments that act as cables within the cell

• Anchors organelles and stabilizes position of the nucleus

Microtubules

• Type of cytoskeletal fiber composed of tubulin dimers

• Used as girders within the cytoskeleton

• Work with motor proteins to move organelles and vesicles around within the cytoplasm

• Involved in cell division (mitotic spindle)

Mitochondria

• Large, complex organelle in which aerobic cellular respiration occurs in eukaryotic cells

• 70S bacterial ribosome

• Two lipid membranes

• Mitochondrial matrix

Nucleus

• Houses the DNA genome in eukaryotic cells (multiple linear DNA chromosomes)

• Controls all activities of the cell and serves an essential role in reproduction and heredity

Nucleolus

A dense region within the nucleus where ribosomal RNA (rRNA) biosynthesis and ribosome assembly occurs

Eukaryotic ribosome

40S small subunit, 60S large subunit, complete 80S ribosome

Free ribosome

• Found in the cytoplasm

• Serve to synthesize water-soluble proteins

Membrane-bound ribosomes

• Attached to the rough endoplasmic reticulum

• Make proteins for insertion into the cell membrane or proteins destined for export from the cell

Peroxisome

• Membrane-bound organelle that is not part of the endomembrane system

• Make and break down hydrogen peroxide

• Amino acids and fatty acids breakdown

• Synthesize lipids

Endomembrane system

A series of membranous tubules, sacs, and flattened disks that synthesize many cell components and move materials around within the cell

Lysosomes

• Membrane-bound organelles of the endomembrane system that contain digestive enzymes

• Breaks down/digests and scavenges

Endoplasmic reticulum (ER)

An interconnected array of tubules and cisternae (flattened sacs) with a single lipid bilayer

Rough endoplasmic reticulum (RER)

Studded with ribosomes bound on the cytoplasmic side of the membrane, which make proteins destined for the plasma membrane

Smooth endoplasmic reticulum (SER)

• Does not have ribosomes

• Involved in biosynthesis of lipids, carbohydrate metabolism, and detoxification of toxic compounds within the cell

Golgi apparatus

• Composed of a series of membranous disks (dictyosomes), each having a single lipid bilayer, that are stacked together

• Enzymes modify lipids and proteins transported from the ER, often adding carbohydrate components to them to produce glycolipids/proteins or proteoglycans

• Cis (incoming package) and trans (outgoing package)

Fungi

• Can be unicellular (e.g., yeast) or multicellular (e.g., mold, mushrooms)

• Absorb nutrients from organic matter (no photosynthesis)

• Have cell walls made of chitin

• Reproduce via spores