Microbial Growth

Cards (96)

  • Microbes that are “growing” are increasing in number, accumulating into colonies.
  • many bacteria survive and grow slowly in nutrient-poor environments by forming biofilms.
  • Growth Factors may require small amounts of certain organic compounds for growth because they are essential substances that the organism is unable to synthesize from available nutrients.
  • The requirements for microbial growth can be divided into two main categories: physical and chemical.
  • Three physical requirements
    1. Temperature
    2. pH
    3. Osmotic Pressure and Salinity
  • Temperature - Most microorganisms grow well at the temperatures that humans favor.
  • Psychrophiles – cold-loving microbes living at 0°C
  • Psychrotrophs – a particular group of psychrophiles, prefer refrigerator temperature (4°C)
  • Psychroduric microbes –prefer warm temperatures but can endure very cold or even freezing temperature
  • Mesophiles – moderate temperature-loving microbes withstanding 25 to 40°C; the most common type of microbe
  • Thermophiles – heat-loving microbes withstanding 50 to 60°C
  • Hyperthermophiles – have an optimum growth temperature of 80°C or higher
  • Extreme thermophiles - 121°C and above
  • pH – refers to the acidity or alkalinity of a solution
  • Most bacteria grow best in a narrow pH range near neutrality, between pH 6.5 and 7.5
  • Acidophiles – bacteria that loves acidic environment (pH of 2 to 5)
    Alkaliphiles - bacteria that loves basic or alkaline environment (pH of >8.5)
  • Plasmolysis is a condition in which the cell membrane and cytoplasm of a cell shrink away from the cell wall; it occurs when bacteria with rigid cell walls are placed in a hypertonic solution.
  • When the concentration of solutes outside a cell is less than that of solutes inside a cell, the solution in which the cell is suspended is said to be hypotonic
  • If a bacterial cell is placed into a hypotonic solution, it may not burst (because of the rigid cell wall). If it does burst, the cytoplasm escapes; this process is known as plasmoptysis.
  • A solution is said to be isotonic when the concentration of solutes outside a cell equals the concentration of solutes inside the cell.
  • Osmotic pressure is the pressure that is exerted on a cell membrane by solutions both inside and outside the cell.
  • Osmosis is the movement of a solvent, through a permeable membrane, from a lower concentration of solutes (dissolved substances) to a higher concentration of solutes
  • When the concentration of solutes in the external environment of a cell is greater than that of solutes inside the cell, the solution in which the cell is suspended is said to be hypertonic.
  • Determine which is hypotonic, isotonic, and hypertonic
    A) isotonic
    B) hypotonic
    C) hypertonic
  • Obligate aerobes – organisms that require oxygen to live.
  • Facultative anaerobes – microbes that can grow in the absence of oxygen
  • Obligate anaerobes – microbes that are unable to use molecular oxygen for energy-yielding reactions
  • Aerotolerant anaerobes – cannot use oxygen for growth, but they tolerate it fairly well
  • Microaerophiles – they re aerobic; they do require oxygen. They grow only in oxygen concentrations lower than those in air
  • Capnophiles – organisms that grow best in the presence of increased concentrations of CO2 (usually 5%–10%)
  • Organisms that prefer to live in salty environments are called halophilic organisms.
  • Extreme Halophiles – require high salt concentration
  • Obligate Halophiles – require 30% of salt for growth
  • Facultative Halophiles – requires 15% of salt for growth
  • Microbes that do not prefer to live in salty environments but are capable of surviving there are called haloduric organisms
  • Barometric Pressure - Microbes that can survive in high atmospheric pressure (>14.7 psi) are known as piezophiles
  • All living protoplasm contains six major chemical elements: carbon, hydrogen, nitrogen, phosphorus, and sulfur
  • Combinations of these and other elements make up vital macromolecules of life, including carbohydrates, lipids, proteins, and nucleic acids.
  • Elements such as iron, copper, molybdenum, and zinc serve as trace elements
  • Microbes also need organic growth factors for it to grow and survive in its environment.