Chapter 6: Microbial Growth Flashcards
Microbial growth
Increase in # of cells of microorganism
Psychrophiles
Psychrophiles optimal temp: for growth 15 degrees celsius
Max growth temp: 20 degrees Celsius
Psychrotrophs
-For growth: 25 degrees celsius
-Growth between 0 and 20-30 degrees celsius (refrigerator 4-8)
-Cause food spoilage
-Ex. Listeria monocytogenes
-Deli meats, unpasteurized dairy products
-Causes sepsis and meningitis in neonates and immunocompromised pt’s
-Multiplies inside phagocytes
Mesophiles
Grow at 25-40 degrees celsius
Optimal temp.: 35-37 degrees celsius (body temp)
Ex. pathogens
Thermophiles
-heat-loving
-produce endospores
-Grow best between 50-60 degrees celsius
-Ex. Clostridium and Bacillus (both gram-(+) rods)
Hyperthermophiles
-heat-loving
-produce endospores
-Grow 80 degrees celsius or higher
“Extreme thermophiles”
Food preservation danger zone
-25 degrees Celsius (room temp)
-rapid growth of bacteria
-some may produce exotoxins➡️ food intoxication when ingested
-common cause of food intoxication: Staphylococcus aureus
-cause vomiting and stomach discomfort in healthy pt’s
Physical requirements for growth: pH
-Most bacteria grow between pH 6.5-7.5
-Molds and yeasts grow at pH 5
-Acidophiles grow at pH <4
Extreme halophiles
-grow in ⬆️[salt]
-30% NaCl solution
-found in seawater
Obligate halophiles
-require salt to grow
-optimal salt concentration: 15-30%
Facultative halophiles
-do not require salt but can grow w/ salt present (2-15% salt can grow)
-Ex. Staphylococcus
Requirements for growth: chemical requirements
-Nitrogen- component of AA’s
-Carbon- synthesis of molecules that make up a living cell
-Sulfur- in some AA’s
-Phosphorus- for ATP; in phospholipids and nucleic acids
-hydrogen- source of e-‘sand component of organic molecules
Chemical requirements for growth: trace elements
-Inorganic mineral elements required in small amounts
-Usually act as enzyme cofactors (metal ions)
-Ex. include iron, copper, zinc, magnesium
Obligate aerobes
-require O2
-ex. Bacillus anthracis
Grows toward top of tube
-optimal amount of O2: 20%
Facultative anaerobes
-Grow w/ or w/o O2 (through anaerobic respiration or fermentation)
-Grows throughout tube (but more concentrated toward the top)
-optimal O2 level: 20%
Obligate anaerobes
-harmed by O2
-ex. Clostridium
-grow at bottom of tube
-Gram-(+)
-endospore -forming
-Rod
-Put in anaerobic jar
-Cause botulism
Aerotolerant anaerobes
-use fermentation to produce ATP
-are not affected by O2
-will grow evenly distributed throughout the tube, meaning it can be found at all levels, from the top to the bottom, as it can tolerate oxygen but doesn’t require it to grow
-ex. Lactobacillus
-rod
-gram-(+)
Microaeophiles
-require low O2
-optimal O2 level: 2-5% O2
-Find area in tube where O2 is 2-5%
-Campylobacter (causes diarrhea and salmonella) and Helicobacter
What will occur if bacterium that normally lives is GI tract is plunged into salty solution?
Plasmolysis (cell losses water and shrinks)
Chemical requirements: organic growth factors
-organic compounds that bacteria need to grow
-Essential compounds that the microbe can not make itself
-Fastidious organisms
-one with complex or specific nutritional needs, making it difficult to grow in a laboratory setting
-Ex. AA’s, vit’s, purines and pyrimidines, NAD+
Biofilms
-Microbial communities form slime of hydrogels
-Clumps of bacteria adhering to a surface- Attached to each other, and the surface is attached to the water
-microbes in biofilms are more resistant to antibiotics than a free-swimming microbes
Characteristics of biofilms
-Bacteria attracted by chemical signaling
-Sheltered/protected from harm factors (antibiotics, disinfectants and host defenses)
-heterogeneity of biofilm community- constantly changing in structure and composition over time
Pseudomonas
-found in wet environments like soil and water
-often involved in biofilms
-Pseudomonas aeruginosa
-survives harsh environments
-common in hospitals and plant surfaces
Culture media
-cultured medium is any material prepared for the growth of bacteria in a lab
-Nutrients prepared for microbial growth
-Sterile: no living microbes- autoclave
-Inoculum: intro of microbes of medium
-Culture: microbes growing in/on culture medium ((s) of (l))
-1) Solid media- nutrients in petri dish containing agar-nutrient
-2) liquid media- nutrient broth in test tube