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.
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 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
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
Production of ATP in Electron Transport Electrochemical Gradient Formed between membranes H+ (Protons) generated from NADH Electrical Force (+) & pH Force (Acid) Gradient formed ATPase enzyme that channels H+ from High to Low concentration
The proteins that mediate the passage of solutes through membranes are referred to as transport systems, carrier proteins, porters, and permeases. Transport systems operate by one of three transport processes. The proteins that mediate the passage of solutes through membranes are referred to as transport systems, carrier proteins, porters, and permeases. Transport systems operate by one of three transport processes. In a uniport process, a solute passes through the membrane unidirectionally. In symport processes (cotransport) two solutes must be transported in the same direction at the same time; in antiport processes (exchange diffusion), one solute is transported in one direction simultaneously as a second solute is transported in the opposite direction.
passive diffusion passive diffusion facilitated diffusion ion-driven transport binding protein dependent transport group translocation
Membrane is selectively permeable Membrane is selectively permeable
Passive processes Passive processes - no energy (ATP) required
- Along gradient
- simple diffusion, facilitated diffusion, osmosis
Simple diffusion Simple diffusion Facilitated diffusion
Osmosis
Active processes Active processes - energy (ATP) required
- Active transport
- Group translocation
One of the most important factors One of the most important factors - temperature range at which the highest rate of reproduction occurs
optimal growth temperature for human pathogens ????
Microorganisms can be categorized based on their optimal temperature requirements Microorganisms can be categorized based on their optimal temperature requirements - Psychrophiles
- Mesophiles
- Thermophiles
Most bacteria are mesophiles especially pathogens that require 37 ºC
Psychrophiles Psychrophiles - some will exist below 0 oC if liquid water is available
- oceans
- refrigerators
- freezers
Mesophiles Mesophiles - most human flora and pathogens
Thermophiles Thermophiles - hot springs
- effluents from laundromat
- deep ocean thermal vents
Aerobe – utilizes oxygen and can detoxify it Aerobe – utilizes oxygen and can detoxify it obligate aerobe - cannot grow without oxygen (Mycobacterium tuberculosis, Micrococcus spp., Bacillus spp., Pseudomonas spp. facultative anaerobe – utilizes oxygen but can also grow in its absence (Echericihia spp., Salmonella spp., Sta[phylococcus spp.) microaerophylic – requires only a small amount of oxygen (Helycobacter spp., Lactobacillus spp.)
Anaerobe – does not utilize oxygen Anaerobe – does not utilize oxygen obligate anaerobe - lacks the enzymes to detoxify oxygen so cannot survive in an oxygen environment (Clostridium spp., Bacteroides spp.) aerotolerance anaerobes – do no utilize oxygen but can survive and grow in its presence (Streptococcus pyogenes)
All microbes require some carbon dioxide in their metabolism. All microbes require some carbon dioxide in their metabolism. capneic – grows best at higher CO2 tensions than normally present in the atmosphere (Brucella abortus)
Microbial growth – an increase in a population of microbes rather than an increase in size of an individual Microbial growth – an increase in a population of microbes rather than an increase in size of an individual Result of microbial growth is discrete colony – an aggregation of cells arising from single parent cell Reproduction results in growth
division exactly in half division exactly in half most common means of bacterial reproduction - forming two equal size progeny
- genetically identical offspring
- cells divide in a geometric progression doubling cell number
Growth of culture goes through four phases with time Growth of culture goes through four phases with time 1) Lag phase 2) Log or Logarithmic phase 3) Stationary phase 4) Death or Decline phase
Organisms are adjusting to the environment Organisms are adjusting to the environment - in order to breakdown nutrients, and to be used for growth
Division is at a constant rate (generation time) Division is at a constant rate (generation time) Cells are most susceptible to inhibitors
Dying and dividing organisms are at an equilibrium Dying and dividing organisms are at an equilibrium Death is due to reduced nutrients, pH changes, toxic waste and reduced oxygen Cells are smaller and have fewer ribosomes In some cases cells do not die but they are not multiplying
1) viable plate count 1) viable plate count 2) direct count 3) most probable number (MPN)
Most common procedure for assessing bacterial numbers Most common procedure for assessing bacterial numbers - 1) serial dilutions of a suspension of bacteria are plated and incubated
2) the number of colonies developing are then counted - 2) the number of colonies developing are then counted
3) by counting the colonies and taking into account the dilution factors the concentration of bacteria in original sample can be determined - 3) by counting the colonies and taking into account the dilution factors the concentration of bacteria in original sample can be determined
- 4) only plates having between 30 and 300 colonies are used in the calculations
5) multiply the number of colonies times the dilution factor to find the number of bacteria in the sample - 5) multiply the number of colonies times the dilution factor to find the number of bacteria in the sample
- Example
- Plate count = 54
- Dilution factor = 1:10,000 ml
- Calculation
- 54 X 10,000 = 540,000 bacteria/ml
“TNTC” “TNTC” - if the number of colonies is too great (over 300) the sample is labeled “TNTC”
- Too Numerous To Count
limitation of viable plate count - selective as to the bacterial types that will grow given the incubation temperature and nutrient type
Calculate: Calculate: - 42 colonies
- dilution factor of 100,000
- 42 X 100,000 = ???
- 4,200,000 bacteria/ml
Ordinary (simple) media Ordinary (simple) media Special media (serum agar, serum broth, coagulated serum, potatoes, blood agar, blood broth, etc.). Elective media Enriched media Differential diagnostic media: (1) proteolytic action; (2) fermentation of carbohydrates (Hiss media); (3) haemolytic activity (blood agar); (4) reductive activity of micro-organisms; (5) media containing substances assimilated only by certain microbes.
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