Bacterial Taxonomy and Indentification Flashcards
Taxonomy
the science that studies organisms in order to arrange them into groups.
Classification
the process of arranging organisms into similar or related groups
Identification
The process of characterizing organisms
Phenotype
refers to the specific characteristics displayed be the organism.
The development and application of molecular techniques, such as nucleotide sequencing, have allowed determination of genetic relatednedd of bacteria
Genotype
charachteristics based on genetic information contianed in the DNA.
Actinobacteria
Phylum contains Gram positive rods and cocci
Proteobacteria
Phylum contians Gram negative bacteria. Most species are aerobic, facultative, or microerophilic.
Bacteroidetes
Phylum contains Gram negative bacterial that are obligate anaerones.
Spirochetes
Phylum contains bacteria that exhibit a unique and complex cellular form of a flexible, extended spiral.
Look like telephone cords
Chlamydia
Phylum contains bacteria that are onligate intracellular organisms and have poor metabolic capabilities.
Firmicutes
Phylum contains Gram positive bacteria, with the exception of Mycoplasmas that lack cell walls and are not Gram positive.
Phenotypic Characteristics
These include; morphology, colony morphology, biochemical traits, and presence of specific proteins are routinely used in Diagnostic Laboratories for identification of bacteria.
Don’t need sophisticated equipment
Growth Characteristics
Bacteria grown in broth or on a solid medium can provide initial clues tohte identity of hte organism. Some bacterial species have characteristic colony morphology, which may provide immediate identity or naroow down the identity.
Microscopic Morphology
This is the first step in identifying a microorganism shape, size and arrangements.
Shape can be cocci, bacilli (rods) or spirals
Arrangements can be singles, pairs, clusters, chains etc.
Simple Stain
This is an aqueous or alcohol solution of a simple basic dye used to visualize shape and arrangements of bacterial cells.
- Methylene blue
- Carbol fuchsin
- Crystal violet, safranin
Differential Stains
These stains react differently with different kinds of bacteria and thus can be used to distinquish groups of bacteria.
- Gram stain
- Acid-fast stain
Gram Stain
The differential stain tha distinguishes between Gram positive and Gram negative bacteria is an expremely useful tool.
rapidly marrows the possible identities of an organism.
Acid-fast Stain
this differentiates bacteria into Acid-fast or non acid-fast based ont he presence of a waxy surface ont he bacterail cell wall.
Waxy coating is called mycoloc acid.
Special stains
These are used to stain specific structures of bacteria, such as capsules, spores, flagella, etc.
Capsules are hard to stain becuase they are water soluble. The backgroun and the cell get stained so visualize the capsule. this is called negative staining because the capsule appears clear.
Biochemical Characteristics
Microscopic and macroscopic characteristics can narrow down the number of possible identities of an organism, but tests to identify biochemical traits are generally necessary for a more conclusive identification.
Most rely on pH indicator or chemical reaction that result in a color change when a compound is degraded.
Polymerase Chain Reaction (PCR)
used to amplify a specific nucleotide sequence present in any sample.
Steps:
- DNA containing the region to be amplified
- Heat stable DNA plymerase
- Add nucleotide bases
- Add in DNA polymerase, primers.
Denaturation
The dsDNA is heated to 95C to separate the strands
Annealing
The temp is lowered to 50C to allow the primers to anneal to their complementary sequence
Elongation
Temp is raised to 70C, which is the optimal temperature for the polymerase.
