Chapter 6: Microbial Growth Flashcards
Psychrophiles
- cold loving organism
types of psychrophiles
- true
- psychrotrophic / faculatative
True psychrophiles
- can grow at 0 degrees
- optimum = 15 degrees
- cannot grow at 20-25 degrees
- non pathogenic
Psychrotrophic / faculatative psychrophiles
- can grow at 0 degrees
- optimum at 20-30 degrees
- cannot grow at 30 degrees
- pathogenic
- causes food (spoilage mild, odour, slimy)
Mesophile
- medium loving organisms
- can grow at 25- 40 degrees
- optimum = 37 degrees
- cannot grow at 50 degrees
- pathogen
types of themophilic organisms
- true
- hyperthermophiles
true thermophilic organism
- cannot grow below 45 degrees
- optimum at 50-60 degrees
- maximum at 70-80 degrees
- non pathogenic
Hyperthermophilic
- cannot grow below 45 degrees
- optimum at 50-60 degrees
- maximum at 110-121 degrees
- non pathogenic
Optimum Ph is typically at
6.5 - 7.5
If a bacteria goes past the optimal ph the bacteria cell wall will
denature
Denaturation
Hypertonic solution effect on the cell
- water moves out of the cell (shrinks)
- plasmolysis
isotinic solution
- no net movement of water
Hypotonic solution effect on the cell
- water moves into the cell (swells)
- if cell burst called osmotic lysis
Obligate Aerobes
- only aerobic growth
- growth occurs where large amount of oxegen difuses into the medium
- contains enzymes catlayse and SOD (nutrilixes toxic forms of oxegen)
- most bacteria
Obligate anaerobic
- only anaerobic growth
- growth occurs where there is no oxygen
- lacks enzymes that neutralize toxic form of oxygen
- harmed by oxygen
example of obligate anaerobic bacteria
- clostridium species
Faculatative anaerobic
- uses oxygen when available for fast growth
- when unavailable uses anaerobic of fermentation (slow growth)
- variable ATP
Example of falculatative aerobic bacteria
- samonella, e-coli
Aerotolerant anaerobes
- tolerate oxygen but choose not to use it
- obligate fermetators
Example of aerotolerant anaerobes
lactobacillus
Microaerophile
- aerobic
- uses oxegen in lower concentrations (2-10%)
- produce small amount of SOD
example of microanerophile bacteria
- helicobacteria (ulcers)
- Campylobacteria jejuni (gastroenteritis)
toxic forms of oxygen include
- singlet oxegen
- superoxide free radicles
- peroxide anion
- hydroxyl radical
Singlet oxygen
- normal oxygen that has been boosted to a higher- energy state and is extremely radioactive
Superoxide free radicles
- toxically caused by instability (steals electrons)
O2- + O2- +2H = 2 H2O2 + O2
Perioxide anion
2 H2O2 —— enzyme: catalase —–> 2 H2O + O2
or
H2O2 + 2H —Enzyme: peroxilase —> 2 H2O
Hydroxyl Radical
(OH)
- most reactive
- formed by cellular cytoplasm by ionizing raditation
Biofilm development
- queron sensing allows microbes
Culture medium
- nutrients prepared for microbial growth
Sterile
- no living microbes
Inoculum
- introductions of microbes in (nutrient broth) / (agar plate) medium
Agar
- complex polysaccaride
- used as a solidifying agent for culture media in peri plates
- is not metabolized by microbes
what temp does agar liquify at
100 degrees
What temp does agar remain solid at
37 degrees
Selective media is made up of
bismuth sulphile agar
Selective media is used to
- supress unwanted microbes and encourage desired microbes
- used to grow organism Samonella typhus (typhoid fever)
Differential media is made up of
blood agar
Deferential media is used to
- distinguish colonies of diffrent microbes
- used to grow streptococcus pyogenes (causes strep throat)
- has clear zome and hemolysis of RBC’s
Selective and differential media is made up of
- manitol salt agar
Selective + differntial media is used to
- grow streptococcus auxeus (skin infections, toxic shock syndrom, food poisoning
- has yellow zone
Steps in Binary Fisson
- cell elongates and DNA is replicated
- cell wall and membrane begin to constrict
- cross wall forms, completely separating the two DNA copies
- cells seperates
Lag phase
- intense activity preparing populaton for growth
Log phase
- logrithmic; exponetial
- increase in population
Generation time formula
(60mins x hours) / (number of generations)
Examples of log phase
- use of antibiotics
- radiation
- antiseptic
Stationary phase
- period of equalibrium
- microbial dealth balance production of new cells
Dealth phase
- population is decreasing at a logarithmic rate
