Studied by 44 people
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
Gram-positive bacteria
Gram-negative bacteria
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
Smearing the creation
Air drying
Heat fixation
Applying crystal violet dye for 1 minute
Rinsing
Flood with iodine for 1 minute
Decolorization with acetone for 5 seconds depending on the specimen; wash immediately.
Counterstain (safranin) for approx. 30 seconds
Wash, blot, dry
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
Smearing the Creation
Flood with Carbol Fuchsin
Heat until Fuschsin evaporated to melt wax covering
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.
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