Cultivation, Reproduction, and Growth of bacteria- MICROBIO OBJECTIVES

requirements of living organisms

carbon, energy source (light or chemicals), nitrogen, phosphorus, sufur, elecemnts, growth factors

Photoautotrophs

light=energy, CO2=carbon

Photoheterotrophs

light=energy, organic compounds=carbon

Chemoautotrophs

inorganic chemicals (NH3, H2S)=energy, CO2=carbon

Chemoheterotrophs

organic compounds=both energy and carbon (most bacteria, fungi, animals)

Defined (synthetic) media 

exact chemical composition known

Complex media

composition not fully known 

Selective media

inhibit some bacteria, allow others

Differential media

show visible differences between bacteria

Enriched media

contain special nutrients

Preparation

sterilization , aseptic technique, pouring into plates/tubes

Application

isolation, identification, maitaining cultures, studying physiology

Psychrophiles

cold, 0 to 30 degrees C (15 C)

Mesophiles

moderate, 25 to 40 degrees C

Thermophiles

heat, 50 degrees C and higher

Optimal growth temperature

specific point where growth is the fastest

Aerobid

require oxygen

Anaerobic

oxygen toxic

Facultatively anaerobic

grow with or without O2

Microaerophilic 

require low oxygen concentration

pH (acidity/ alkalinity)

buffers like phosphate salts maintain stable pH

most bacteria prefer neutral (6.5-7.5)

Energy source

light, organic molecules, or inorganic chemicals

Osmotic pressure

halophiles need salt; most bacteria need moderate osmotic balance

Nutrients

nitrogen, phosphorus, minerals, vitamins

Population increase

increase in cell numbers not cell size

Geometrical / exponential progression

each cell divides- 2,4,8,16, etc.

Generation time 

time needed for the population to double (E.coli~20 mins)

Synchronous cultures

experimental setups where all cells divide together for study

During growth…

bacteria is doubling and grows faster and faster over time 

Generation time

used to measure the growth, which is the amount of time it takes for a population to double

Growth cycle

Lag phase

logarithmic or exponential phase 

stationery phase

decline/death phase

Growth cycles are measured by…

microscopic or plate count, membrane filter, nitrogen or weight determination, or measurment of biochemical activity