History of Microbiology. - History of Microbiology.
- Classification of bacteria.
- Structure of bacterial cell
Morphologic Physiologic Prophylactic
Bergey’s Manual of Systematic Bacteriology - Classifies bacteria via evolutionary or genetic relationships.
Bergey’s Manual of Determinative Bacteriology - Classifies bacteria by cell wall composition, morphology, biochemical tests, differential staining, etc.
Microscopic morphology Microscopic morphology Macroscopic morphology – colony appearance Physiological / biochemical characteristics Chemical analysis Serological analysis Genetic and molecular analysis - G + C base composition
- DNA analysis using genetic probes
- Nucleic acid sequencing and rRNA analysis
Bergey’s Manual of Determinative Bacteriology – five volume resource covering all known procaryotes Bergey’s Manual of Determinative Bacteriology – five volume resource covering all known procaryotes - classification based on genetic information –phylogenetic
- two domains: Archaea and Bacteria
- five major subgroups with 25 different phyla
Domain Domain Kingdom Phylum Class Order Family Genus species
Vol 1A: Domain Archaea Vol 1A: Domain Archaea - primitive, adapted to extreme habitats and modes of nutrition
Vol 1B: Domain Bacteria Vol 2-5: - Phylum Proteobacteria – Gram-negative cell walls
- Phylum Firmicutes – mainly Gram-positive with low G + C content
- Phylum Actinobacteria – Gram-positive with high G + C content
Phylogeny of domain Bacteria Phylogeny of domain Bacteria - The 2nd edition of Bergey’s Manual of Systematic Bacteriology divides domain Bacteria into 23 phyla.
Phylogeny of domain Bacteria (cont.) Phylogeny of domain Bacteria (cont.) - Phylum Proteobacteria
- The largest group of gram-negative bacteria
- Extremely complex group, with over 400 genera and 1300 named species
- All major nutritional types are represented: phototrophy, heterotrophy, and several types of chemolithotrophy
- Sometimes called the “purple bacteria,” although very few are purple; the term refers to a hypothetical purple photosynthetic bacterium from which the group is believed to have evolved
Phylogeny of domain Bacteria (cont.) Phylogeny of domain Bacteria (cont.) - Phylum Proteobacteria (cont.)
- Divided into 5 classes: Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Epsilonproteobacteria
Phylogeny of domain Bacteria (cont.) Phylogeny of domain Bacteria (cont.) - Phylum Proteobacteria (cont.)
- Significant groups and genera include:
- The family Enterobacteriaceae, the “gram-negative enteric bacteria,” which includes genera Escherichia, Proteus, Enterobacter, Klebsiella, Salmonella, Shigella, Serratia, and others
- The family Pseudomonadaceae, which includes genus Pseudomonas and related genera
- Other medically important Proteobacteria include genera Haemophilus, Vibrio, Camphylobacter, Helicobacter, Rickessia, Brucella
Phylogeny of domain Bacteria (cont.) Phylogeny of domain Bacteria (cont.) - Phylum Firmicutes
- “Low G + C gram-positive” bacteria
- Divided into 3 classes
- Class I – Clostridia; includes genera Clostridium and Desulfotomaculatum, and others
- Class II – Mollicutes; bacteria in this class cannot make peptidoglycan and lack cell walls; includes genera Mycoplasma, Ureaplasma, and others
- Class III – Bacilli; includes genera Bacillus, Lactobacillus, Streptococcus, Lactococcus, Geobacillus, Enterococcus, Listeria, Staphylococcus, and others
Phylogeny of domain Bacteria (cont.) Phylogeny of domain Bacteria (cont.) - Phylum Actinobacteria
- “High G + C gram-positive” bacteria
- Includes genera Actinomyces, Streptomyces, Corynebacterium, Micrococcus, Mycobacterium, Propionibacterium
- Phylum Chlamidiae
Phylogeny of domain Bacteria (cont.) Phylogeny of domain Bacteria (cont.) - Phylum Spirochaetes
- The spirochaetes
- Characterized by flexible, helical cells with a modified outer membrane (the outer sheath) and modified flagella (axial filaments) located within the outer sheath
- Important pathogenic genera include Treponema, Borrelia, and Leptospira
- Phylum Bacteroidetes
- Includes genera Bacteroides, Flavobacterium, Flexibacter, and Cytophyga; Flexibacter and Cytophyga are motile by means of “gliding motility”
Binomial naming system Binomial naming system First word is genus name Second word is species name When writing full name genus usually abbreviated Full name always italicized
Storage granules Storage granules - Metachromatic granules
- Polysaccharide granules
- Lipid inclusions
- Sulfur granules
- Carboxyzomes
- Magnetosomes
Gas vesicles
Unique chemical structure Unique chemical structure - Distinguishes Gram positive from Gram-negative
- bacteria and archaea bacterial species
Rigidity of cell wall is due to peptidoglycan (PTG) - Compound found only in bacteria
- Archaea –psudomurein or other sugars, proteins, glycoproteins
Many antimicrobial interfere with synthesis of PTG
Basic structure of peptidoglycan - Alternating series of two subunits
- N-acetylglucosamin (NAG)
- N-acetylmuramic acid (NAM)
- Joined subunits form glycan chain
- Glycan chains held together by string of four amino acids
- L-ala-D-glu-DAP-D-ala
- L-ala-D-glu-Lys-D-ala
Interpeptide bridge
Capsule Capsule - Protects bacteria from phagocytic cells
Slime layer - Enable attachment and aggregation of bacterial cells
3 parts 3 parts - filament – long, thin, helical structure composed of proteins
- hook- curved sheath
- basal body – stack of rings firmly anchored in cell wall
rotates 360o 1-2 or many distributed over entire cell functions in motility
1. Monotrichous – single flagellum at one end (cholera vibrio, blue pus bacillus), 1. Monotrichous – single flagellum at one end (cholera vibrio, blue pus bacillus), 2. Lophotrichous – small bunches arising from one end of cell (blue-green milk bacillus, Alcaligenes faecalis) 3. Amphitrichous – flagella at both ends of cell (Spirillum volutans), 4. Peritrichous – flagella dispersed over surface of cell, slowest E. coli, salmonellae of enteric fever and paratyphoids A and B
Short, hair-like structures on the surfaces of procaryotic cells Short, hair-like structures on the surfaces of procaryotic cells Proteinaceuse filaments (~20 nm in diameter) Very common in Gram-negative bacteria Functions: - Adherence to surface/ substrates: teeth, tissues
- Involved in transfer of genetic information btw cells
- Have nothing to do with bacterial movement (Except the twitching movement of Pseudomonas)
Bacterial spores are often called “endospore” (since they are formed within the vegetative cell) Bacterial spores are often called “endospore” (since they are formed within the vegetative cell) Produced in response to nutrient limitation or extreme environments Highly resistant Highly dehydrated (15% water) Metabolically inactive Stable for years Not reproductive Functions: to survive under an extreme growth conditions such as high temperature, drought, etc.
Bacillus, Clostridium, Sporolactobacillus, Thermoactinomyces, Sporosarcina, Desulfotomaculum species sporulate
Key compositions: Key compositions: - Dipicolinic acid (DPA)
- Calcium (Ca2+)
Structure - Core / Cytoplasm
- Plasma membrane
- Core wall/ spore wall
- Cortex
- Spore coat
- Exosporium
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