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
Temperature
pH
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.