BACTERIA GROWTH REQUIREMENT Flashcards
- Infectious organisms have specific growth requirements.
o Temperature
o Ph (physical)
o Osmotic pressure
o Atmosphere (oxygen)
o Nutrients (chemical) - These specific requirements allow for a maximum increase in a number of infectious organisms.
- Increased numbers of pathogens help to defeat the host defense.
Bacterial growth
– An orderly & organized in SUM of all components
Growth
– in number of cells & not in size
Microbial growth
– composed of billions of cells
Bacterial colony
o heat-loving bacteria
o Grows best if higher than 40c
Thermophile
o Have absolute or obligate need for oxygen
o Example: Micrococcus species
- Obligate/ strict aerobes
o Cannot multiply if any oxygen is present, often killed even if w/ traces of oxygen
o Example: Clostridium (Clostridium botulinum)
- Obligate anaerobes
o Require small o2 (2% to 10%) for aerobic resp
o Example: Helicobacter pylori (cause of gastric & duodenal ulcer)
o Example: Spirillum volutans (an aquatic habitant)
Microaerophiles
o Grows w/ o2, but can also grow without it.
o Example: E. Coli & yeast saccharomyces
Facultative anaerobes
o Can grown with o2 presence, but do not use it to transform energy
o Example: Streptococcus pyogenes
Aerotolerant anaerobes
o Grows at pH above 8.5
Alkalophile
o Most medically important bacteria
o Multiples bet. Ph 5 to 8
Neutrophile
o Cold loving bacteria
o Bet. 10C to 20C
Psychrophiles
o Requires addition of carbon dioxide to enhance grow
Capnophiles
o require optimal temperature
o Bet. 20C to 40C
o Grows in human body- medically IMPT
Mesophiles
o Grows at Ph below 5
Acidophile
- Bacteria cell is composed mainly of water
- Serves as medium from which bacteria acquired their nutrients
Except: bacteria endospores, protozoan cyst
Water/ moisture availability
o Requires high osmotic pressure
o Can tolerate a hypertonic environment
Osmotolerant
o Requires high level of NaCl/ salt.
Halophile
Utilizes inorganic compound (ex. carbon dioxide) &
inorganic salt as source of carbon
Autotrophs/Lithotrophs
- requires light for photosynthesis
- Photoautotrophs
- Uses organic substances; Utilizes glucose and water as carbon source
Heterotrophs/Organotrophs
- Energy derive from light
Phototroph
- Energy derive from chemical substances
Chemotroph
- Organisms that derive their energy by the oxidation of inorganic substances like sulfur
Chemolithotrophs
- Organisms that obtain energy from the oxidation of reduced organic compounds
Chemoorganotrophs
– 4% sulfur & phosphorus; 14% nitrogen
Dry wt of bacteria
- For synthesis of ATP & nucleic acid
Nitrogen & phosphorus
- For synthesis of protein
Nitrogen & sulfur
- Stabilizes ribosomes, cell membrane & nucleic acids; co-factor in activity of enzymes
Magnesium
- fxning of ribosomes, enzymes activity
Potassium
- Component of cytochrome (parts of electron transport chain); cofactor in enzyme activity
Iron
- Component of gm (+) cell wall; for resistant endospores
Calcium
– cofactor in enzyme activity, maintenance of protein structure
Iron Trace elements (manganese, zinc, copper, cobalt)
o Promotes growth & development
Pyrimidines
Purines
Vitamin B
Amino acids
Growth factor
- Illustrates the phases in the growth of the population of the bacteria when they are grown in a culture in a fixed volume.
- Bacterial Growth Curve
o may last for 1-4hours
o characterized by cellular activity but not growth.
o period of adjustment for the bacteria in the new environment
o Absorbs nutrients
o Prepare for cell division
o No increase in number
- Lag Phase
o Multiplies rapidly & double in each generation time generation time (binary fission)
o antibiotics and disinfectants are most effective
o Cells are metabolically active
o Average duration of this phase is about 8 hours
- Log phase/ logarithmic/ exponential phase
o Equilibrium/ growth slows down
o The culture is at its greatest population density
o The # of bacteria that are dividing equal the number of dying
o Spore forming bacteria produce endospores
o Pathogenic bacteria generate toxin
- Stationary phase
o Concentration of waste product increase while the nutrients decreases
o Sporulation may occur in some bacteria
o Nutrients become less available and waste products increase
o Number of dying cells continue to rise
o Nutrients available to help spore producing to survive long enough for spore production
- Death (or decline phase)
o The division of one cell into two cells, after DNA REPLICATION & the formation of a separating membrane & cell wall
o Parent cell splits in half to become 2 daughter cell.
BINARY FISSION
o Before it divides in half, its chromosome must be duplicated first.
DNA REPLICATION
o The time it takes for binary fission to occur.
o Varies from one bacterial species to another & also depends on the growth condition
GENERATION TIME
Steps in the pathogenesis of infectious diseases
- Entry
- Attachment
- Multiplication
- Invasion or spread:
- Evasion of host defenses
- Damage to host tissues
- Developed in 18th century by Carolus Linnareus
- Binomial system = 2 names
o E.g. homo sapiens (human)
Nomenclature
