JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD Pharm. D II Year PHARMACEUTICAL MICROBIOLOGY Previous Question Paper (July/August - 2021 - R08)

Microbial classification is the systematic arrangement of microorganisms into groups based on their similarities, evolutionary relationships, and phenotypic characteristics. The primary goal is to provide a structured framework for identification and nomenclature.

The classification is broadly organized into the following systems:

1. Taxonomic Hierarchy: Microorganisms are classified into a hierarchical structure: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species. The binomial nomenclature system, introduced by Linnaeus, uses the Genus and species names to uniquely identify an organism.
2. Three-Domain System: Based on Carl Woese's analysis of ribosomal RNA, all life is divided into three domains: Bacteria (prokaryotes), Archaea (prokaryotes with distinct biochemical characteristics), and Eukarya (organisms with membrane-bound nuclei, including fungi, protozoa, and algae).
3. Phenotypic Classification: This relies on observable characteristics, including:
   • Morphology: Cell shape (cocci, bacilli, spirilla), size, and arrangement.
   • Staining reactions: Gram staining, acid-fast staining, and spore staining.
   • Biochemical properties: Metabolic capabilities, such as enzyme production, fermentation patterns, and carbon source utilization.
   • Physiological requirements: Temperature tolerance, pH sensitivity, and oxygen requirements (aerobic, anaerobic, or facultative).
4. Genotypic and Phylogenetic Classification: Modern techniques focus on genetic makeup, including:
   • G+C content: The ratio of guanine and cytosine in the DNA.
   • DNA-DNA hybridization: Measuring the degree of genetic similarity between two organisms.
   • rRNA sequencing: Comparing 16S rRNA sequences to determine evolutionary distance.
   • Whole-genome sequencing: Providing the most precise data for taxonomic placement.
5. Numerical Taxonomy: A computer-assisted approach where numerous characteristics are assigned equal weight, and organisms are grouped based on the percentage of shared features (similarity coefficients).

This multifaceted approach ensures that microorganisms are accurately categorized, which is essential for clinical diagnosis, industrial fermentation, and the development of pharmaceutical products.