(MMI) Exam 1 Review: Lectures 1 - 7

Classes of Microorganisms

Bacteria, fungi, protozoa, algae, virus

Study of bacteria

Bacteriology

Study of fungi

Mycology

Study of viruses

Virology

Study of infectious protozoa and parasitic worms

Parasitology

Beneficial microbes compete against harmful microbes

Probiotics

Largest photosynthesizers (microbes) in the ecosystem

Phytoplankton

Decomposers of organic waste

Fungi

He looked at the structure of cork and reported that living things were composed of little boxes or cells (in 1665). He proposed that the cell was the smallest component or building block of living things

Robert Hooke

Aseptic techniques prevent

- Infections as a result of surgery

- Food spoilage

- Contamination in microbiology laboratories

He developed a very simple microscope and used it to describe the nature and behavior of live microorganisms that he observed in teeth scrapings, rain water, etc... (1673-1723)

Antonie van Leeuwenhoek

Life is created from non-living matter by some "vital force"

Spontaneous generation theory

Life can only arise from pre-existing living matter

Biogenesis theory

In 1745, John Needham put boiled nutrient broth into covered flasks. It resulted in microbial growth. This suggests

Spontaneous generation

In 1765: Lazzaro Spallanzani boiled nutrient broth solutions in flasks. It resulted in no microbial growth. This suggests

Biogenesis

In 1861, his experiment showed that microorganisms are present in the air.

Louis Pasteur

He used a chemical disinfectant to prevent surgical wound infections after looking at Pasteur's work showing microbes are in the air, can spoil food, and cause animal diseases.

Joseph Lister

He proved that a bacterium causes anthrax and provided the experimental steps, known as "Koch's postulates", to prove that a specific microbe causes a specific disease.

Robert Koch

He made the first vaccine (for smallpox)

Edward Jenner

Vaccination is derived from this latin word which means cow

Vacca

Chemicals produced by bacteria and fungi that inhibit or kill other microbes.

Antibiotics

Malaria was treated using (Collected from tree bark)

Quinine (a natural bitter alkaloid derived from the bark of the cinchona tree)

Chemotherapeutic agents used to treat infectious disease

Synthetic drugs/antibiotics

He discovered the first antibiotic.

Alexander Fleming

What antibiotic did The fungus Penicillium made?

Penicillin

The antibiotic penicillin helps to fights against which microbe?

Staph. aureus

The study of how the host responds to the infecting micro-organism

Immunology

Four types of microscopy

- Light Microscopy (Brightfield, Darkfield, Phase contrast, Differential interference contrast (DIC))

- Electron microscopy (Scanning & Transmission)

- Fluorescence microscopy

- Confocal microscopy

A simple microscope such as that used by van Leeuwenhoek has only one lens.

Light microscopy

In a compound microscope, the image from the objective lens is magnified again by the

Ocular lens

Objective lens x ocular lens

Total magnification

The ability of the lenses to distinguish between two points

Resolution

Shorter wavelengths of light provide

Greater resolution

A microscope with a resolving power of 0.4 nm can distinguish between two points

≥ 0.4 nm

Due to the relatively long wavelength of light in a compound light microscope, the effective limit on resolution is

200nm (= 0.2 μm)

Dark objects are visible against a bright background. Contrast staining is often required to see objects.

Brightfield microscopy

Light objects are visible against a dark background because only light reflected off the specimen enters the objective lens. Staining usually not required.

Darkfield microscopy

Accentuates diffraction of the light that passes through a specimen. Can visualize living specimens without staining.

Phase-contrast microscopy

It is similar to phase-contrast microscopy but has a higher resolution because it uses two beams of light. Prisms split the light beams adding contrasting colours to the specimen.

Differential Interference Contrast (DIC) Microscopy

It uses electrons instead of light. The shorter wavelength of electrons gives greater resolution.

Electron microscopy

Transmission electron microscopy (TEM)

- Magnification 10 - 100 000x

- Resolution ~ 2.5 nm

- Need ultra-thin sections of specimen to allow electron passage.

- Specimens may be stained with heavy metal (electron dense) salts such as uranium or osmium tetroxide.

Scanning electron microscopy (SEM)

- Magnification 1 - 10 000x

- Resolution ~ 20 nm

- Examine whole cells or surface structures

- Electron beam is sprayed over the sample scattering electrons from its surface structures which are collected and amplified to produce a 3d image.

- Specimens may also be stained with heavy metal (electron dense) salts such as uranium or osmium tetroxide to provide contrast.

It uses ultraviolet (U.V.) light and the cells may be stained using fluorescent dyes.

Fluorescence microscopy

It uses fluorochrome dyes to stain the cells and a laser light. The laser illuminates and captures an image for each plane in a specimen.

Confocal microscopy

Two photons of long-wavelength (red) light are used to excite the dyes so it can examine thicker samples/cells (up to 1 mm deep).

Two-photon microscopy

A thin film of a solution of microbes is spread on a slide.

Smear

Use of a single basic dye.

Simple stain

It may be used to hold the stain or coat the specimen to enlarge it.

Mordant

Staining the background instead of the cell

Negative staining

It classifies bacteria as either gram-positive or gram-negative.

Gram staining

A means of discriminating one type or class of cell from another.

Differential stains

Appears purple under microscope

Gram-positive bacteria

Appears red under microscope

Gram-negative bacteria

Gram staining procedure

- Prepare the slide using heat fixing

- Apply Crystal Violet (stain) and let it sit for 1 minute. Wash it off with water.

- Flood the slide with Gram's iodine (mordant) and wash it using water after 1 minute.

- Rinse the slide using Ethanol (decolorizer) and wash it with water immediately after.

- Apply Safranin and wash it off after 1 minute.

Cells that retain a basic stain in the presence of acid-alcohol.

Acid-fast

Very hydrophobic structures that enhance the virulence of certain microbes.

Capsules

What staining is useful for observing capsules?

Negative staining

It requires a mordant to make the flagella wide enough to see.

Flagella staining

It is used to detect the presence of endospores in bacteria.

Endospore staining

This term comes from the Greek words for prenucleus. It includes bacteria and cyanobacteria.

Prokaryote

This term comes from the Greek words for true nucleus. It includes fungi, algae, protozoa, plants & animals.

Eukaryote

Spherical cells

Cocci (coccus)

Rod shaped cells

Bacilli (bacillus)

Curved (spiral) cells

Vibrio

Helical, flexible cells

Spirochetes

Helical, rigid cells

Spirilla (spirillum)

Unusual e.g. star shaped or rectangular

Archaea

Means double

Diplo-

Means twisted chain

Strepto-

Means cluster

Staphylo-

Means group of four

Tetrad

Means bundle

Sarcinae

Bacteria with one shape throughout life.

Monomorphic

Bacteria with several morphologies

Pleiomorphic

Outside components of prokaryotic cells

Glycocalyx, Cell wall, Flagella, Fimbriae, & Pili

Inside components of prokaryotic cells

Cell membrane, Cytoplasm, Nucleoid, Ribosomes, Endospores & Inclusion bodies

Simple polysaccharide chains layered just outside cell wall. It protect cell from drying out; protect against phagocytosis; allow cell to colonize a new niche.

Glycocalyx

Flagella (flagellum) is composed of chains of a protein called

Flagellin

A single flagellum at the end of the cell.

Monotrichous

A single flagellum or a tuft of flagella at both ends of the cell.

Amphitrichous

A tuft of flagella at the end of the cell.

Lophotrichous

An all-over, random flagellar arrangement.

Peritrichous

Axial filaments (they're found in spirochetes) are also known as

Endoflagella

They're not used for motility. They're shorter and straighter than flagella

Fimbriae

They're longer than a fimbriae. They're used to transfer DNA from one cell to another.

Pili (pilus)

The process of transferring DNA from one cell to another.

Conjugation

It provides support and protection; determines cell shape. It also prevents bursting of cell (in hypotonic solution).

Bacterial cell wall

Lipid A (lipopolysaccharide) is an example of an

Endotoxin (toxic molecules made of (LPS) that form the outer cell wall of Gram-negative bacteria)

It provides some protection from host defenses (phagocytes, complement) and antibiotics. It is composed of lipopolysaccharides, lipoproteins, phospholipids.

Gram negative outer membrane

They're not present in eukaryotic cells therefore treatments which selectively attack this will not affect human or animal cells.

Peptidoglycan: a tough, mesh-like polymer made of sugars and amino acids that surrounds the plasma membrane

A gel-like solution of water and organic and inorganic substances; contains all internal structures.

Cytoplasm

It functions as a selective barrier to limit entry and exit of materials.

Plasma membrane

Similar structure between prokaryotes and eukaryotes

- Phospholipid bilayer

- Peripheral proteins

- Integral proteins

- Transmembrane proteins

A passive transport process in which a molecule passes directly across the membrane down its concentration gradient with no expenditure of cell energy.

Simple diffusion

A passive transport process in which a molecule crosses the membrane down its concentration the gradient with the aid of premise.

Facilitated diffusion

An energy-requiring process in which a transport protein pumps a molecule across the membrane against its concentration and/or electrical gradient.

Active transport

It contains single, long, almost always circular thread of double stranded DNA.

Nucleoid

Separate smaller strands/circles in the nuclei.

Plasmids

They're present in both eukaryotes and prokaryotes. They're the protein synthesis machinery of the cell.

Ribosomes

Two subunits of the ribosomes are composed of (small subunit 30S + large subunit 50S = Complete 70S ribosome).

Protein and ribosomal RNA