5. bacterial classification & identification Flashcards
this is the classification of organism in an ordered system that indicates a natural relationship
bacterial taxonomy
what are the three areas of bacterial taxonomy?
- identification
- classification
- nomenclature
this is the practical side of taxonomy; the process of determining that a particular isolate belongs to a recognized taxon
identification
this is the categorization of organisms into taxonomic groups based on mutual similarities, genetic and evolutionary relatedness
classification
this refers to the naming of an organisms by an established group of scientific and medical professionals
nomenclature
what are the 4 different classical characteristics of the classification of bacteria
- morphological characteristics (size and shape)
- physiological and metabolic characteristics (motility, growth range)
- biochemical characteristics (products bacteria gives)
- ecological characteristics (from what part of the environment the bacteria came from)
T/F: nomenclature of bacteria is bolded
false - italicized or underlined
what is the first part of the generic name?
genus
what is the second part of the generic name?
species
what is the most common bacteria shape?
cocci - roughly spherical shapes
what bacterial shape is a rod shape?
baccilli
what does coccobacilli mean
short bacilli
these are curved bacteria that can range from a gently curved shape to a corkscrew-like spiral
spirilla
what is the most formative method for identifying bacteria?
staining and microscopy
this type of microscopy is particularly useful for detection of bacteria, fungi and parasites.
light microscope
this type of microscopy is useful for observing very small bacteria as the resolution is quite high
dark-field microscope
this is similar to dark field microscopy, except that light source is ultraviolet, and the organisms are stained with fluorescent compounds. the specimen is seen as a halo around only the organism tagged with fluorescent compounds
fluorescence microscope
why do we stain bacteria?
to become more visible under the microscope or to visualize specific parts or organelles within the cell
this type of ionizable dyes used to stain microorganisms have positively charged groups that can bind to negatively charged structures such as DNA and cell membranes. e.g. methylene blue, basic fuchsin, crystal violet, safranin, and malachite green
basic dyes
this type of ionizable dye used to stain microorganisms have negatively charged groups and can stain positively charged cell proteins and organelles. e.g. eosin, rose bengal and fuchsin
acid dyes
this divides bacteria into separate groups based on staining properties
differential stainingg
this is the most important type of differential staining; this divides bacteria into two groups: gram-positive and gram-negative bacteria, based on the structure of the cell wall
gram stain
explain the process of gram staining
- apply a basic dye (crystal violet) and iodine solution - all bacteria will be stained blue
- decolorization step: the cells are treated with alcohol - gram positive cells will retain the crystal violet-iodine complex, remaining blue and the gram negative cells are completely decolonized by the alcohol
- a counterstain, safranin which is red, is applied so that the gram negative cells will be stained red and the gram positive cells will appear purple
this process is used to stain bacteria that do not simply stain with regular procedure. this method is usually used to stain mycobacterium tuberculosis (causes tuberculosis), mycobacterium leprosy (causes leprosy - affects nerves, skin eyes) and actinomycetes bacteria
acid fast stain (Ziehl-Neelsen method)
the __________ (acid-fast/non-acid-fast) bacteria take the red color of carbofuchsin dye
acid fast bacteria
the ________ (acid-fast/non-acid-fast) bacteria take the color of the counterstain (blue or green)
non-acid fast bacteria
this stain treats the cells with tannic acid salts to increase the thickness of this structure. then it is stained with basic fuchsin and the structure will then be able to be seen in a light microscope
the flagella stain
the staining of this structure is stained by Feulgen stain
nucleoids (DNA)
the wall of this structure is relatively impermeable, so they can be observed as colourless areas in cells stained by conventional stains
to stain this structure, malachite green or carbolfuchsin are applied with heat. the vegetative part of the cell can be stained with another counterstain after the decolorization step
the spore stain
this structure is stained by the Welch method: the cells are treated with a hot crystal violet solution, they are then rinsed with a copper sulfate solution in order to remove excess crystal violet and give a dark color to the background
the capsule stain
this type of medium is a medium in which the exact chemical composition is known
defined medium
this type of medium is a medium in which the exact chemical constitution of the medium is not known (good for growing bacteria)
complex medium
this type of media supports the growth of many different bacterial species without selection, such as blood agar and chocolate agar (blood agar boiled makes the brown color) media.
nonselective media
this type of media is used to eliminate the large numbers of irrelevant bacteria in the specimens. it has an inhibitory agent that specifically selects against the growth of these irrelevant bacteria. examples of inhibitory agents: sodium azide, bile salts and colistin and nalidixic acid. examples of this media: MacConkey agar and CNA blood agar
selective media
this inhibitory agent selects for gram positive over gram negative bacteria
sodium azide
this inhibitory agent selects for gram negative enteric bacteria and inhibit gram negative mucosal and most gram positive bacteria
bile salts
this inhibitory agent inhibits the growth of many gram negative bacteria
colistin and nalidixic acid
this media is used to differentiate between bacterial groups; some bacteria produce characteristic pigments, and others produce zones of clearing surrounding colonies
differential media
these are tests used for the identification of bacteria species based on the differences in the biochemical activities of different bacteria
biochemical test
the bacterial species can be divided or classified into subgroups called serotype, serogroups or serovars based on the _____________________ reactions
immunological
the immunologic tests are based on _____ that react with specific bacterial cell surface structures such as lipopolysaccharides (o antigen), flagella (h antigen) or capsular antigens (k antigen)
antibodies
under certain circumstances (e.g. an epidemic), it is important to distinguish amoung strains of a given species or to identify a particular strain below the species level which is known as ________
subtyping
