Module 2: Classification and Identification of Bacteria, Fungi, and Viruses Flashcards
The science that involves classification, identification, and nomenclature of microorganisms.
Taxonomy
What are the 3 important terms that are commonly encountered in the study of bacterial classification?
Classification
Identification
Nomenclature
It involves the orderly arrangement of microorganisms into groups. This involves arranging together or distinguishing microorganisms that are different from each other as a means of bringing order to a variety of organisms.
Classification
True or False
There is no unified basis of classification, different groups of scientists and experts have the capacity to classify even the same organisms differently.
True
True or False
Some microbiologists can classify organisms based on serotype,
antimicrobial resistance pattern, toxins and invasiveness factors in one pathogen while others may be interested in genes which are concerned with mutations and plasmids.
True
Basic taxon
Species
A group of microorganisms that possess characteristics analogous to other species within the genus.
Genus
A group of microorganisms that possess characteristics analogous to
other genera within the family.
Family
A group of microorganisms possess characteristics analogous to other
families within the order.
Order
It includes groups of microorganisms that possess characteristics
analogous to other orders within the class.
Class
Composes of a group of microorganisms that possess characteristics analogous to other classes.
Division
It constitutes a group of microorganisms that possess characteristics analogous to other members of a division.
Kingdom
It involves the practical use of classification criteria to distinguish certain organisms from others, to verify the authentic nature of a strain and to isolate and identify the organism that causes an infection.
Identification
It involves the giving of an official name to a species of microorganism by which the characteristics of that species are defined and communicated among members of the scientific community. The designated names are often derived from names of persons, shapes or forms of microbes.
Nomenclature
True or False
Names are always written in binomials (2 words).
True
True or False
Binomials are italicized or underlined.
True
What are the three-domain or large groups in the classification system of microorganisms which was introduced by Carl Woese and his colleague in 1990?
Archaea
Bacteria
Eukarya
Domains _______ and _______ are made up of prokaryotic cells.
Bacteria
Archaea
Domain _______ is made up of eukaryotic cells.
Eukarya
This domain includes microorganisms that are associated with human or animal diseases. Most bacterial species do not cause disease but many of them reportedly play beneficial roles by producing antibiotics and food. The soil inhabited by free-living bacteria that perform many essential functions in
the biosphere (nitrogen fixation). The human body is covered with bacteria that make up the normal flora.
Bacterial domain
This domain includes methanogens (methane-maker), extreme halophiles (salt lovers) and extreme thermophiles (heat/cold lovers). The
methanogens reportedly live in swamps, marshes, gut of cattle, termites, and other living substrates.
Archaen domain
A domain that covers the protista, fungi, plants and animals. The protists include the single celled eukaryotes like euglena, amoeba, paramecium and protozoa.
Eukarya domain
Cell shape, color, nature of cellular aggregates, motility-related organelles and formation of spores are important criteria in bacterial classification. Morphological features such as shape and color of colonies are purported to be not always constant and can be influenced by environmental conditions.
Morphological-based classification
Gram staining and the application of other stains for bacteria are important methods in evaluating bacterial morphology. Of all the
different classification systems, the Gram stain has reportedly withstood the test of time.It allows a large proportion of clinically important bacteria to be classified as either
Gram-positive or Gram-negative based on their morphology and different staining properties. Slides are sequentially stained with crystal violet, iodine, then decolorized with alcohol and counter-stained with safranin. Gram-positive bacteria stain blue-purple and Gram-negative bacteria stain red.
Staining reactions
Important in the classification of bacteria is the conduct of biochemical tests including the determination of the kinds of nutrients a bacterium can use, the products of its metabolism, the response to specific chemicals, and the presence of particular characteristic enzymes.
Biochemical features
Microorganisms can be grouped on the basis of their need for oxygen to grow. Facultatively anaerobic bacteria can grow in high oxygen or low oxygen content and are among the more adaptable bacteria. In contrast, strictly anaerobic bacteria grow only in conditions where there is minimal or no oxygen present in the environment.
Growth requirements
Bacterial antigens include surface proteins, lipopolysaccharides and peptidoglycan
structures that help bacteria invade host cells by gaining access between epithelial cells. Studies on surface structures are important in recognizing the ability of bacteria to infect hosts while this also helps in the recognition and
classification of potential pathogens.
Antigenic composition, habitat and disease production
Selected antisera are reportedly used to classify different bacterial species. This may be based on either carbohydrate or protein antigens from the bacterial cell wall or the capsular polysaccharide.
Serologic systems
Microorganisms can also be classified based on the ultrastructure of the bacteria revealed under the electron microscope. This utilizes samples which are processed as thin sections and subjected to negative staining before electron microscopic evaluation.
Electron microscopy
The classification of the 3 domains for
all living organisms– bacteria, archaea and eucarya were reportedly based on the comparison of 16s ribosomal RNA sequences. These sequences are highly conserved and undergo change at a slow, gradual and consistent rate which makes comparisons among the different living organisms easier.
Genotypic and molecular analysis
This classifies microorganisms-based gene-controlled metabolic patterns, production of cell polymers and organ structures. It embraces studies on DNA homology and composition, DNA sequences which evaluate surface polymers (Ex: capsules, teichoic acids and O-antigens) and used as references for comparison of bacterial relatedness.
Genetic basis of classification