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Microbial Growth and Culture Media in Microbiology

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Termini in questo insieme (27)

  • Physical requirements for microbial growth
    Include temperature, pH, and osmotic pressure essential for microbial survival and reproduction.
  • Chemical requirements for microbial growth
    Include carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen, and organic growth factors.
  • Minimum, optimum, and maximum growth temperatures
    Minimum is the lowest temperature a species grows, optimum is the best growth temperature, and maximum is the highest temperature allowing growth.
  • Microbial temperature groups
    Psychrophiles (-10 to 20°C), Mesophiles (10 to 50°C), Thermophiles (40 to 72°C), and Hyperthermophiles (65 to 110°C).
  • pH range for bacterial growth
    Most bacteria grow between pH 6.5 and 7.5, molds and yeasts between pH 5 and 6, and acidophiles in acidic environments.
  • Effect of osmotic pressure on microbes
    Hypertonic environments cause plasmolysis due to high osmotic pressure, inhibiting microbial growth.
  • Halophiles
    Microbes that require or tolerate high salt concentrations; extreme halophiles require it, facultative halophiles tolerate it.
  • Role of carbon in microbial growth
    Carbon is the structural backbone of organic molecules; chemoheterotrophs use organic molecules, autotrophs use CO2.
  • Trace elements in microbial growth
    Inorganic elements like iron, copper, molybdenum, and zinc required in small amounts as enzyme cofactors.
  • Oxygen requirement classifications
    Obligate aerobes require oxygen, facultative anaerobes grow with or without oxygen, anaerobes harmed by oxygen, aerotolerant anaerobes tolerate oxygen, microaerophiles need low oxygen.
  • Organic growth factors
    Organic compounds like vitamins, amino acids, purines, and pyrimidines obtained from the environment.
  • Biofilms
    Microbial communities forming slime or hydrogels that adhere to surfaces, communicate via quorum sensing, share nutrients, and resist microbicides.
  • Culture medium
    Nutrients prepared for microbial growth; can be sterile and inoculated with microbes to grow cultures.
  • Agar
    A complex polysaccharide used as a solidifying agent in culture media; liquefies at 100°C and solidifies around 40°C.
  • Chemically defined media
    Media with exact known chemical composition, used for growing chemoautotrophs and fastidious organisms.
  • Complex media
    Contain extracts and digests of yeasts, meat, or plants; chemical composition varies and supports most chemoheterotrophs.
  • Reducing media
    Contain chemicals like sodium thioglycollate to remove oxygen, used for cultivating anaerobic bacteria.
  • Selective media
    Suppress unwanted microbes and encourage growth of desired microbes using inhibitors.
  • Differential media
    Allow distinguishing colonies of different microbes on the same plate by visible changes.
  • Enrichment culture
    Encourages growth of a desired microbe by increasing its numbers to detectable levels, usually in liquid media.
  • Pure culture
    Contains only one species or strain; isolated using the streak plate method.
  • Colony
    A population of cells arising from a single cell or spore, often called a colony-forming unit (CFU).
  • Binary fission
    A form of bacterial cell division where one cell divides into two identical daughter cells.
  • Generation time
    The time required for a cell to divide or a population to double, ranging from 20 minutes to 24 hours.
  • Phases of bacterial growth
    Lag phase: metabolic activity without cell increase; log phase: rapid cell division; stationary phase: equilibrium; death phase: cell death exceeds new cells.
  • Direct methods of measuring microbial growth
    Include plate counts, filtration, most probable number (MPN), and direct microscopic counts.
  • Indirect methods of measuring microbial growth
    Include turbidity measurement, metabolic activity, and dry weight of cells.