Module 4

Microbial Diversity: Prokaryotes

Prokaryotes

It is comprised of two domains: Bacteria and Archaea

Domain Archaea

It means “ancient”. Originally assigned when it was thought that these prokaryotes evolved earlier than bacteria. Many, but not all are extremophiles, in the sense that they live in extreme environment.

Peptidoglycan

It is a complex macromolecular polymer found in the bacterial cell wall. It is tough rigid envelope that protects them from environmental stress.

Three Major Classifications According to Staining

1. Gram-positive bacteria
2. Gram-negative bacteria
3. Lacks cell wall

Simple Stain

Sufficient to determine the bacterial shape and morphologic arrangement. After the basic preparations, a dye is applied. It is then rinsed and observed.

Structural Staining

Procedure used to observe the bacterial capsule, spores, and flagella.

Differential Staining

Procedure that enables microbiologists to differentiate one group of bacteria from another.

Steps in Differential Staining

1. Smearing the creation
2. Air drying
3. Heat fixation
4. Applying crystal violet dye for 1 minute
5. Rinsing
6. Flood with iodine for 1 minute
7. Decolorization with acetone for 5 seconds depending on the specimen; wash immediately.
8. Counterstain (safranin) for approx. 30 seconds
9. Wash, blot, dry
10. Observe

Gram-positive

Bacterium is blue to purple at the end of Gram staining procedure or after decolorization of acetone.

Gram-negative

Bacterium ends up pink to red after counter stain and washing

Acid-Fast Staining

It is used to classify gram-variable bacteria and is useful for TB Lab.

Steps in Acid-Fast Staining

1. Smearing the Creation
2. Flood with Carbol Fuchsin
3. Heat until Fuschsin evaporated to melt wax covering
4. Decolorization with Acid Alcohol Mixture

Carbol Fuchsin

A deep red dye

Cocci, Bacilli, Spirilla, Pleomorphic

The basic shapes of bacteria

Cocci

It is a round or spherical bacteria

Bacilli

May be short, long, thick or thin, and pointed or curved or blunt.

Coccobacilli

Some rods which are quite short resembling elongated cocci.

Diphtheroids

Some bacilli stack up next to each other, side by side in a palisade arrangement.

Vibrio cholerae

It is the cause of cholera. It is a curved shaped bacilli

Spirillum

It is a helical-shaped and appears corkscrew-like

Campylobacter spp.

It is a common cause of diarrhea that has gull wing morphology

Spirochetes

A spiral-shaped bacteria. Example of this bacteria are Treponema pallidum and Borrelia spp.

Treponema pallidum

It is a spirochete that causes syphilis

Borrelia spp.

It is a spirochete that causes Lyme disease.

Pleomorphic Bacteria

Exist in various shapes due to absence of cell walls.

Motile bacteria

Most spiral-shaped bacteria and about one-half of bacilli

Nonmotile bacteria

Cocci in general

Gliding motility

Some bacteria secretes slime to do this type of motility

Agar Stabbing Technique

It is used to determine if a bacteria is motile or not by stabbing the bacteria into a tube of semisolid agar.

**Non-motile bacteria**: will only grow along the stab line

**Motile bacteria**: will spread away from the stab line

Binary Fission

The primary method of reproduction for prokaryotic cells.

Obligate aerobes

Require an atmosphere containing molecular oxygen concentrations comparable to that found in room air. They are also highly transmissible transmissible.

Microaerophiles

Needs oxygen for multiplication but in concentrations lower than that found in room air.

Obligate anaerobes

Can grow better in an anaerobic environment

Aerotolerant anaerobes

Does not require oxygen, grows better in the absence of oxygen, but can survive in an atmosphere containing molecular oxygen.

Facultative anaerobes

Capable of surviving in either presence or absence of oxygen.

Capnophile

Microorganisms that thrive in the presence of high concentrations of carbon dioxide.

Fastidious Bacteria

Require special/complicated nutritional supplements and conditions to grow

Bacterial Virulence

It refers to the ability to cause diseases.

Glycocalyx

It is a gel-like meshwork that surrounds the cell.

Rudimentary Bacteria

These are unique bacteria which are formerly thought to be viruses. They do not possess typical characteristics of a bacterial cell.

Rickettsia

They appears to have a leaky cell membrane

Coxiella burnetti

It causes Q fever which is transmitted through aerosols and ticks.

Bartonella quintina

It causes Trench fever which is a louse-borne disease, cat scratch disease, bacteremia, and endocarditis.

Ehrlichia and Anaplasma

It causes human tickborne disease.

Chlamydia

They are referred to as energy parasites.

Chlamydia Trachomatis

Trachoma is the leading cause of blindness, conjunctivitis, and nongonococcal urethritis.

Chlamydia Pneumoniae

It causes pneumonia

Chlamydia Psittaci

It causes psittacosis

Mycoplasma

It is the smallest of all cellular microbes and is formerly known as pleuropneumonia-like organism.

Thylakoids

Intracellular membrane attached to the cell wall. Have **phycobilisomes** that are used to harvest light.

Cyanobacteria

It does oxygenic photosynthesis. They use light as an energy source and produce oxygen.

Cyanotoxins

These are cyanobacteria that produces toxins

Acidophiles

They live in extremely acidic environments.

Alkaliphiles

They live in alkaline

Thermophiles

They live in hot environment.

Psychrophiles

They live in cold environment.

Halophiles

They live in salty environment.

Piezophiles

They live in highly pressurized environment.

Methanogens

An archaea that produces methane gas, which is a flammable gas.