Microbial Diversity

Acellular Microbes

- also known as infectious particles.

- includes Prions and Viruses.

Cellular Microbes

- also called microorganisms

- Includes Prokaryotes and Eukaryotes

Prokaryotes

- organisms with cells that lack true nucleus.

- Includes Archaea and Bacteria

Eukaryotes

- Organisms with cells that have true nucleus

- includes Algae, Protozoa, and Fungi

Pathogens

- Microbes that cause disease

Nonpathogens

- Microbes that do not cause disease

Indigenous Microbia

-Microbes that live on and in the human body

Opportunistic Pathogens

pathogens that do not causes disease under normal conditions but have the potential to cause disease if there's opportunity.

Infectious Diseases

when a pathogen inhabits the body and cause disease

Microbial Intoxications

when a person ingest a poisonous substance that has been produced by a pathogen outside the body.

Anton van Leeuwenhoek (1632 - 1723)

invented the microscope lens that allowed visualization of organisms

Theory of Spontaneous Generation

- idea that life arises from nonliving material

- also known as "abiogenesis"

Louis Pasteur (1882 - 1895)

- introduced terms "aerobes" and "anaerobes"

- Developed Pasteurization process.

- theorized that specific microbes cause specific diseases.

- developed vaccines

Pasteurization

treating a substance with heat to kill or slow the growth of pathogens

Robert Koch (1843 - 1910)

- Established Koch's postulates - a sequence of experimental steps that verified the germ theory

- Identified cause of anthrax, TB, and cholera

- Developed pure culture methods

Koch's Postulate 1

the microorganism must be found in similarly diseased animals but not in healthy ones

Koch's Postulate 2

The microorganism must be isolated from a diseased organism and grown in pure culture.

Koch's Postulate 3

The cultured microorganism should cause disease when introduced into a healthy organism.

Koch's Postulate 4

The organism should be re-isolated and shown to be the same as the original

Germ Theory of Disease

idea that infectious diseases are caused by microorganisms and not by "unbiblical theories"

Exception to Koch's Postulates

Some pathogens cannot be grown in pure culture. Ex: Mycobacterium leprae

- human volunteers are difficult to obtain and ethical considerations limit their use

Robert Hooke (1635-1703)

- Invented the compound microscope.

- First to observe cells in 1665.

- Coined the term "Cells" from cork.

Rudolf Virchow (1821-1902)

Proposed the "The Theory of Biogenesis"

Theory of Biogenesis

life can arise only from preexisting life, and, therefore, cells can only arise from preexisting cells.

Eukaryotic Cell Structure

- have true nucleus

- cells are enclosed and by cell membranes

- 80s ribosome density

Svedberg Unit

unit for sedimentation rate, how fast particle settles (sediments)

Histones

protein molecules around which DNA is tightly coiled in chromatin

Mycoplasma

genus of bacteria that does not have a cell wall.

Prokaryotic Cell Structure

- 10 times smaller than eukaryotes

- Cell membranes enclose cytoplasm

- 70s ribosomes density

Spheroplast

A gram-negative bacterium treated to damage the cell wall, resulting in a spherical cell.

L-Forms

- gram-positive or gram-negative bacteria that naturally have a cell wall but lose it during part of their life cycle
- pleomorphic

General Shapes of Bacteria

cocci (round)
bacilli (rod-shaped)
spiral-shaped

Cocci Arrangements

-diplococci = two cocci
-streptococci = chains of four or more
-staphylococci = grape clusters
-tetrads = packs of four cocci
-octads - packs of eight

Pleomorphic

many shapes

pleomorphism

ability to exist in a variety of shape

Heat Fixation

a technique that uses the heat from a flame to attach a smear to a slide

-the sample is passed about 5 times into the flames

Methanol Fixation

flood the smear with absolute (95%) methanol for 130 seconds and remove by tilting the slide

preserves bacterial morphology

Simple Staining (Structural Staining Procedure)

- Use 1 basic stain (ex: Methylene blue) to color cells.

- Allows for visualization of the cells size, shape, arrangement, and number.

Negative Staining

- staining the background instead of the cell

- requires Indian ink or nigrosine

Endospore Staining

uses heat in order for malachite green stain to penetrate the endospore

Flagella Staining

mordant applied to increase thickness of flagella

Dr. Hans Christian Gram (1884)

developed the "Gram Staining Procedure"

Steps in Gram Staining

1. push crystal violet(1 minute)
2. rinse, put iodine (1 minute),
3. rinse, decolorize, ethanol (15seconds),
4. wash
5. safranin (30 seconds)
6. wash in water, blot, air dry.

Gram-positive bacteria

- Bacteria that have a thick peptidoglycan cell wall, and no outer membrane.

- They stain very darkly (purple) in Gram stain.

Gram-negative bacteria

- Bacteria that have a thin peptidoglycan cell wall

- They stain very lightly (pink) in Gram stain.

Acid-fast staining

developed by Paul Elrich in 1882

used to identify Mycobacterium species

Steps in Acid-fast Staining

1. primary dye: carbol fushin: colors acid-fast bacteria red
2. decolorizer: generally acid alcohol: removes stain from non-acid fast bacteria
3. counter stain: methylene blue: colors non acid fast bacteria blue

Acid-fast bacteria

Retain the primary stain even when treated with acid alcohol.

Mycobacterium

- the only acid-fast bacteria in our sputum or saliva

Motility

- ability to move

- presence of axial filaments or flagella

Flagella

A long, whip-like filament that helps in cell motility.

Axial Filaments

- Found in spirochetes
Anchored at one end of a cell
- Rotation causes cell to move like a corkscrew

Flagella Arrangement

Monotrichous = single flagellum.
Lophotrichous = tufts of flagella at one end.
Amphitrichous = single flagella at both ends.
Peritrichous = flagella over entire cell.
Amphilophotrichous = tufts of flagella at both ends.

Colony

a mound or pile of bacteria on the surface of a solid culture medium

Atmospheric Requirements

Bacteria can be classified on the basis of their atmospheric requirements, including their relationship to O2 and CO2

Capnophiles

Microbes that require high CO2 conditions

Obligate aerobes

require O2 to survive

Microaerophiles

require oxygen concentration lower than air

Aerotolerant anaerobes

do not utilize oxygen but can survive and grow in its presence

facultative anaerobes

can live with or without oxygen

Obligate anaerobes

can only grow in an environment without oxygen

Thioglycollate broth

the region of medium in which the organism grows depending on the oxygen it needs

Methods for Cultivation of Anaerobes

Candle Jar Method and gas Generator or Gas-Pak Jar Method

Temperature Requirements

some bacteria can grow at near freezing or hot temperatures

fastidous organism

any organism that has a complex nutritional requirement

Pathogenecity

ability of a microorganism to produce disease

Pili

Appendages that allow bacteria to attach to each other

Fimbriae

similar to pili but shorter, used for attachment to surfaces

Microbial Infection

microorganism itselt is the causative agent

microbial intoxication

a disease that results from ingestion of a toxin that was produced by a pathogen in vitro (outside the body)

Exoenzymes

enzymes secreted outside the cell wall

Genetic Composition

Bacteria are identified using some type of procedure that analyzes their DNA or RNA

Halophiles

salt - loving

thermophiles

heat - loving

hyphae

The branching, threadlike tubes that make up the bodies of multicellular fungi

superbugs

antibiotic resistant bacteria

mycelium

mass of hyphae

sporangium

sacs that contains spore