1: Basic Microbiology and Infection Control
- Page ID
- 77471
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Microbiology is the study of microscopic organisms, those being unicellular (single cell), multicellular (cell colony), or acellular (lacking cells). As an application of microbiology, medical microbiology is often introduced with medical principles of immunology as microbiology and immunology. Otherwise, microbiology, virology, and immunology as basic sciences have greatly exceeded the medical variants, applied sciences.
- 1.1: Classification - The Three Domain System
- Phylogeny refers to the evolutionary relationships between organisms. Organisms can be classified into one of three domains based on differences in the sequences of nucleotides in the cell's ribosomal RNAs (rRNA), the cell's membrane lipid structure, and its sensitivity to antibiotics. The three domains are the Archaea, the Bacteria, and the Eukarya. Prokaryotic organisms belong either to the domain Archaea or the domain Bacteria; organisms with eukaryotic cells belong to the domain Eukarya.
- 1.2: Sizes, Shapes, and Arrangements of Bacteria
- There are three basic shapes of bacteria: coccus, bacillus, and spiral. Based on planes of division, the coccus shape can appear in several distinct arrangements: diplococcus, streptococcus, tetrad, sarcina, and staphylococcus. The bacillus shape can appear as a single bacillus, a streptobacillus, or a coccobacillus. The spiral shape can appear in several forms: vibrio, spirillum, and spirochete.
- 1.3: The Peptidoglycan Cell Wall
- The vast majority of the domain Bacteria have a rigid cell wall composed of peptidoglycan. The peptidoglycan cell wall surrounds the cytoplasmic membrane and prevents osmotic lysis. Peptidoglycan is composed of interlocking chains of building blocks called peptidoglycan monomers.
- 1.4: Structures Outside the Cell Wall
- In this section on Prokaryotic Cell Anatomy we are looking at the various anatomical parts that make up a bacterium. We will now look at the following structures located outside the cell wall of many bacteria: (1) glycocalyx (capsule) and S-layer, (2) flagella, and (3) pili.
- 1.5: Cellular Components within the Cytoplasm
- Various anatomical parts that make up the anatomy of a Prokaryotic Cell bacterium. As mentioned in the introduction to this section, a typical bacterium usually consists of: a cytoplasmic membrane surrounded by a peptidoglycan cell wall and maybe an outer membrane; a fluid cytoplasm containing a nuclear region (nucleoid) and numerous ribosomes; and often various external structures such as a glycocalyx, flagella, and pili.
- 1.6: An Overview to Control of Microorganisms
- Control of microorganisms is essential to prevent the transmission of diseases and infection, stop decomposition and spoilage, and prevent unwanted microbial contamination. Microorganisms are controlled by physical agents and chemical agents. Physical agents include methods as controlling temperature, desiccation, osmotic pressure, radiation, and filtration. Control by chemical agents refers to the use of disinfectants, antiseptics, antibiotics, and chemotherapeutic antimicrobial chemicals.
- 1.7: Ways in which Chemical Control Agents Affect Bacteria
- The basis of chemotherapeutic control of bacteria is selective toxicity. Selective toxicity means that the chemical being used should inhibit or kill the intended pathogen without seriously harming the host. A broad spectrum agent is one generally effective against a variety of Gram-positive and Gram-negative bacteria; a narrow spectrum agent generally works against just Gram-positives, Gram-negatives, or only a few bacteria. Such agents may be cidal or static in their action.
- 1.8: Ways in which Bacteria May Resist Chemical Control Agents
- Most bacteria become resistant to antibiotics by way of one or more mechanisms that are coded for by genes in the bacterial chromosome and/or in bacterial plasmids. Bacterial genes may code for production of an enzyme that inactivates the antibiotic. Bacterial genes may code for an altered target site receptor (ribosomal subunit, enzyme, etc.) for the antibiotic to reduce or block its binding. Bacterial genes may code for altered membrane components.
Thumbnail: A diagram of a typical prokaryotic cell. (Public Domain; LadyofHats).