MICROBIAL GROWTH
Microorganisms grow in a variety of physical & chemical environments. Growth of microorganism depends on the ability of a cell to form a new cell from the nutrients available in the environment. Growth involves increase in cell mass, number of organelles, duplication of bacterial chromosomes & the synthesis of new cell wall and plasmamembrane.
Microbial growth as defined by Campbell, is the doubling of every biochemical unit of a cell within the time duration of a single division without a change in the rate of growth.
Doubling time for most bacteria is 15-20min, Yeast take 45min for its division while molds take 4-8 hrs to complete its division.
MICROBIAL GROWTH IN BATCH CULTURE
(CLOSED SYSTEM)
A batch culture is that in which growth of microorganisms occurs in a limited amount of nutrients.
During growth in batch culture, the number of microorganisms increase logarithmically(exponentially) for some time (i.e. each cell give rise to 2 cells, which inturn give rise to 4 cells and so on) and finally reach the death phase.
Growth of microorganisms in batch culture has 4 distict phases;
1. LAG PHASE
2.LOG PHASE
3. STATIONARY PHASE
4. DEATH PHASE