MICROBIAL GROWTH Flashcards
Temperatures
Minimum growth temp. - lowest temp. at which species will grow
Optimum growth temp. - temp. at which the species grows best
Maximum growth temp. - highest temp. at which growth is possible
Cold-loving microbes
Psychrophiles
0°C - 15 °C
Most likely encountered in low-temperature food spoilage cause they grow fairly well at refrigerator temp.
Psychotrophs 20-30°C
Psychotrophs do not grow well at low temperatures but they
Slowly degrade food
Common method of food preservation
Refrigeration
Common type of microbes
Mesophiles 37°C
Moderate-temp. loving microbes
Mesophiles
Mesophiles lives in
Adapted to live in the bodies of animals
Optimum temp. for many pathogenic bacteria
20 - 40 °C
Heat-loving microbes
Thermophiles
Optimum growth temp. of thermophiles
50-60 °C
Formed by thermophilic bacteria are unusually heat resistant
Endospores
Thermophiles will not grow in what temp?
Below 45°C
Hot springs associated with volcanic activity and sulfur is usually important in their metabolic activity
Hyperthermophiles
Optimum growth temperature of hyperthermophiles
80°C
Extreme Thermophiles
Hyperthermophiles
Most bacteria grow best on what pH range?
pH range near neutrality (7)
Have high tolerance to acidity
Acidophiles
Very few bacteria grow at what acidic pH?
below pH 4
Microorganisms require water for growth, and their composition is
80-90% water
Microorganisms obtain almost their nutrients in solution form the surrounding water
Osmotic pressure
This osmotic loss of water causes
Cell shrinkage of cell’s cytoplasm
Addition of salts or other solutes to a solution, and the resulting increase in
Osmotic pressure
Can be used to preserve foods
Salt or sugar
Adapted so well to high salt concentration that they actually require them for growth
Halophiles
Organisms from saline waters (dead sea)
Obligate halophiles
Chemical requirements
Carbon, nitrogen, sulfur, phosphorus and oxygen
It is needed for all the organic compounds that make up a living cell
Carbon
Important elements to synthesize cellular material
Nitrogen, sulfur and phosphorus
Bacterias that use oxygen to extract more energy from nutrients
Aerobes
Bacterias that does not use oxygen
Anaerobes
Bacterias that requires oxygen to live
Obligate aerobes
They use oxygen when it is present but are able to continue growth by using fermentation or anaerobic respiration when oxygen is not available
Facultative anaerobes
Facultative anaerobes use oxygen when present but are able to continue growth by using
Fermentation or Anaerobic respiration
Phases of bacterial growth
Lag phase - Intense activity preparing for population growth, but no increase in population.
Log phase - Logarithmic or exponential increase in population
Stationary phase - Period of equilibrium; microbial deaths balance production of new cells.
Death phase - Population is decreasing at a logarithmic rate.
The logarithmic growth in the log phase is due to
Reproduction by Binary fission (bacteria) or Mitosis (yeast)
Denotes the population of microorganisms that inhabit the skin and mucus membranes of healthy normal persons
Normal microbiota
Normal microbiota provides a
- First-line defense against microbial pathogens
- Assists in digestion
- Plays a role in toxin degradation
- Contributes to maturation of the immune system
Two groups of Resident Microbiota
Resident microbiota
Transient microbiota
Consists of relatively fixed types of microorganisms regularly found in a given area at given age
Resident microbiota
Consist of nonpathogenic or potentially pathogenic microorganisms that inhabit body sites for hours, days or weeks
Transient microbiota
Microorganisms that are constantly present on body surfaces. One partner benefits, while the other seems unaffected
Commensals
Both parties derive benefit
Mutualistic
Significance of Normal Flora
- Role in maintaining health and normal function
- Can synthesize important compounds, vitamin K
- Aid in absorption of nutrients
- Prevent colonization by pathogens and possible disease
Involve competition for receptors or binding sites on host cells, competition for nutrients, mutual inhibition by metabolic or toxic products, mutual inhibition by antibiotic materials
Bacterial interference
Opportunity body to be weaker
Opportunistic pathogens
Can normal microbiota cause disease?
Yes. If forcefully removed from the environment and introduced into the bloodstream or tissues, these organisms may become pathogenic
What are the common resident of the Upper Respiratory Tract?
Streptococci viridans
If large bumbers of Streptococci viridans are introduced into the bloodstream, they may settle on deformed or prosthetic heart valves and produce
Infective endocarditis
