Principle of bacterial taxonomy, Lecture notes of Microbiology

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PRINCIPLES OF BACTERIAL TAXONOMY,

TAXONOMICAL RANKS - MOLECULAR

METHODS IN TAXONOMY

ABHISHEK P

INTRODUCTION

• Swedish botanist credited with founding the science of taxonomy. - He introduced the binomial system of nomenclature - Linnaeus also established a hierarchy of taxonomic ranks: species, genus, family, order, class, phylum or division, and kingdom.
• At the highest level, Linnaeus divided all living things into two kingdoms-plant and animal. -In his taxonomic hierarchy each organism is assigned a species name, and species of very similar organisms are grouped into a genus and so on.

TAXONOMY AND SYSTEMATICS

• TAXONOMY - The field of biology that deals with the theory and practice of classification of organism
• Taxonomy term was proposed by de Candolle in 1813 which means law of arrangements
• Systematics is the scientific study of organisms with the ultimate objective of characterising and arranging them in an orderly manner
• A polyphasic approach is used to classify microbes
• This incorporates information gleaned from genetic, phenotypic and phenotypic analysis

EARLY TAXONOMIC SYSTEMS

• Carolus Linnaeus (1753)- use of a species name Based on looking at physical and structural similarities
• He also found the binomial system of nomenclature in which he gave species 2 names - Genus and Species
• This system paved way to new taxonomic systems

5 KINGDOM CLASSIFICATION Whitaker proposed that organisms should be broadly divided into kingdoms, based on certain characters like the structure of the cell, mode of nutrition, the source of nutrition, interrelationship, body organization, and reproduction. According to this system, there are five main kingdoms. They are: -Kingdom Monera -Kingdom Protista -Kingdom Fungi -Kingdom Animalia -Kingdom Plantae

Disadvantages

• There is no place for virus
• Similar organisms are kept far apart from each other for example unicellular and multicellular algae.
• There is diversity in kingdom protista

CLASSIFICATION

2.) POLYPHASIC CLASSIFICATION

Polyphasic taxonomy takes into account all available phenotypic and genotypic data, molecular sequences, evolutionary characteristics, and ecological behaviors in classification of the organisms 3.) PHYLOGENETIC CLASSIFICATION It groups organisms together based on the mutual similarity of their phenotypic characteristics The term “phylogeny” is a Greek word where phylon=tribe or race; and genesis= generation or origin It sought to compare organisms based on their evolutionary relationships. An evolutionary arrangement of species.

4 .) GENOTYPIC CLASSIFICATION It seeks to compare the genetic similarity between organisms by comparing either individual genes or whole genomes

CLASSIFICATION

• The classification of living things helps us in many ways to organize and group organisms based on their characteristics.
• Organism classification takes place in the form of a taxonomic system. This is called the Linnean classification. The Linnean classification involves the usage of the grouping organisms using a hierarchy called taxa.
• This animal classification system contains taxonomic levels and taxonomic groups that animals are placed in based on their features and even shared ancestry.
• These levels of biological classification are as follows: Species » Genus » Family » Order » Class » Phylum » Kingdom » Domain

Biological systematics or phylogeny bears the special name taxonomy, consists of three separate but interrelated parts - classification, nomenclature, identification Classification – arrangement of organisms into groups (taxa; s.,taxon) Nomenclature – assignment of names to taxa Identification – determination of taxon to which an isolate belongs