Serological Testing and Bacterial Identification

Microbiology: An Introduction

• This is a textbook on microbiology, specifically the thirteenth edition.
• The text covers classification of microorganisms.
• It explores the study of phylogenetic relationships, focusing on taxonomy and systematics/phylogeny.
• Taxonomy is the science of classifying organisms.
• Systematics, or phylogeny, studies the evolutionary history of organisms.

The Study of Phylogenetic Relationships

• Linnaeus developed kingdoms for classifying plants and animals.
• The prokaryote was introduced in the 1800s to distinguish from eukaryotes.
• Whittaker's five-kingdom system was introduced in 1968.
• The Murray-kingdom Prokaryotae was proposed in 1968.
• Bacteria and fungi were put into the kingdom Plantae (Nägeli) in the 1800s.
• Protista was proposed by Haeckel.

The Three Domains (Part 1)

• Woese developed the three-domain system in 1978 based on rRNA nucleotide sequences.
• The three domains are Eukarya, Bacteria, and Archaea.
• Eukarya includes animals, plants, and fungi.
• Bacteria is a domain of prokaryotes.
• Archaea includes methanogens, extreme halophiles, and hyperthermophiles.

The Three Domains (Part 2)

• Eukaryotes originated from infoldings of prokaryotic plasma membranes.
• Endosymbiotic bacteria developed into organelles such as mitochondria and chloroplasts.
• A chart shows these processes in a diagrammatic style.

Figure 10.1 Three-Domain System

• Organisms evolved over billions of years.
• DNA is conserved and passed from ancestors.
• Eukarya includes fungi, plants, animals, and protists.
• Bacteria and Archaea are prokaryotes.

Table 10.1 Some Characteristics of Archaea, Bacteria, and Eukarya

• Archaea, Bacteria, and Eukarya are compared based on cell type, cell wall, membrane lipids, the first amino acid in protein synthesis, antibiotic sensitivity, rRNA loop, and common arm of tRNAt.

Table 10.2 Prokaryotic Cells and Eukaryotic Organelles Compared

• Prokaryotic cells have circular DNA (linear in some archaea), no histones, formylmethionine (in bacteria) and methionine (in archaea), 70S ribosomes, and binary fission.
• Eukaryotic cells have linear DNA, histones, methionine, 80S ribosomes, and mitosis.
• Mitochondria and chloroplasts are eukaryotic organelles with a special section with similar prokaryotic structures.

Classification of Eukaryotes

• Protista is a catchall kingdom.
• Fungi are chemoheterotrophic, unicellular or multicellular with chitin walls.
• Plantae are multicellular with cellulose walls that undergo photosynthesis.
• Animalia are multicellular and chemoheterotrophic with no cell walls.

Classification of Viruses

• Viruses are not part of any domain, not composed of cells, and require a host cell.
• Viral species have similar characteristics and occupy a particular ecological niche.

Methods of Classifying and Identifying Microorganisms

• Classification arranges organisms into groups of related species based on characteristics.
• Identification matches unknown organisms to known species' characteristics. This involves clinical laboratory methods.
• Bergey's Manual of Determinative Bacteriology provides identification schemes for bacteria and archaea.
• Lists of bacterial names are approved for classification purposes.

Additional Methods

• Lab requisition forms aid in clinical microbiology by noting specimens and tests in clinical settings.
• Transport media helps collect and transport pathogens to labs.
• Several methods are used, including morphological characteristics, differential staining, biochemical tests (a flowchart showing several steps), rapid identification systems, and automated systems of identification.
• Serology involves studying immune responses of microorganisms in serum. It shows how antisera and serological tests may be helpful for knowing a specimen or culture better.
• Phage typing uses phages to determine bacterial susceptibility.
• Fatty acid profiles and flow cytometry are used, along with nucleic acid hybridization (using probes, DNA chips, and other methods) and DNA sequencing and fingerprint information.
• Ribotyping and FISH are used to see the identity, relative abundance, and the activity of microorganisms in an environment.
• Dichotomous keys are used with a flowchart to identify species.