1) Provided with the right conditions (food, correct temperature, etc) microbes can grow very quickly.
2) Depending on the situation, this could be a good thing for humans (yeast growing in wort to make beer) or a bad thing (bacteria growing in your throat causing strep throat).
3) It's important to have knowledge of their growth, so we can predict or control their growth under particular conditions.
1) Microbial growth: In microbiology, growth is defined as an increase in the number of cells.
2) Bipartition: is the process by which a cell divides to form two equal cells.
3) The interval that elapses in the formation of two cells from one cell is called generation and the time required for this is the generation time or duplication time.
Time it takes for a single cell to go from one division to the next: generation time or doubling time. This is also the time it takes for a population to double.
For many "typical" bacteria under "ideal" conditions this doubling time may be as fast as 20 minutes.
Bacterial population increases exponentially or logarithmically. Exponential growth is only part of the bacterial life cycle, and not representative of the normal pattern of growth of bacteria in Nature.
In the laboratory, under favorable conditions, a growing bacterial population doubles at regular intervals. Growth is by geometric progression: 20, 21, 22, 23, 24, 2n (Where n = the number of generations)
That is: (x)(2)n
initial number of bacterial cells and n=
the number of generations.
1) Lag Phase:
Adaptation period: time necessary to recover from physical damage or shock in the transfer. The population remains temporarily unchanged.
Although there is no apparent cell division occurring, the cells may be growing in volume or mass, synthesizing enzymes, proteins, RNA, etc., and increasing in metabolic activity.
2) Logarithmic (Log) Growth Phase:
The exponential phase of growth is a pattern of balanced growth wherein all the cells are dividing regularly by binary fission, and are growing by geometric progression.
The cells divide at a constant rate depending upon the composition of the growth medium and the conditions of incubation. The rate of exponential growth of a bacterial culture is expressed generation time, (G) is defined as the time (t) per generation (n = number of generations).
Hence, G=t/n is the equation from which calculations of generation time (below) derive.
3) Pre-Stationary Phase:
Challenge period and exponential growth disappears, microorganisms go into stress due to lack of nutrient supply.
4) Stationary Phase:
Exponential growth cannot be continued forever in a batch culture (e.g. a closed system such as a test tube or flask).
Population growth is limited by one of three factors: 1. exhaustion of available nutrients; 2. accumulation of inhibitory metabolites or end products; 3. exhaustion of space, in this case called a lack of "biological space".
5) Death Phase:
If incubation continues after the population reaches stationary phase, a death phase follows, in which the viable cell population declines.
During the death phase, the number of viable cells decreases geometrically (exponentially), essentially the reverse of growth during the log phase.
1. Alcoholic fermentation: Yeasts convert sugars into ethanol, carbon dioxide and other metabolic by-products that contribute to the chemical composition and sensory properties of fermented foods.
2. Homo-fermentative lactic fermentation: One molecule of glucose is ultimately converted to two molecules of lactic acid
3. Heterofermentative lactic fermentation: Produces carbon dioxide and ethanol in addition to lactic acid.
4. Propionic fermentation: Propionic acid fermentation is carried out by several bacteria that belong to the genus Propionibacterium and to the species Clostridium propionicum. During propionic acid fermentation, both sugar and lactate can be used as the initial substrate.
5. Mixed acid fermentation: Mixed acid fermentation is the biological process by which a six-carbon sugar e.g. glucose is converted into a complex and variable mixture of acids.
6. Butyric fermentation: Butyric acid fermentation is characteristic of several obligate anaerobic bacteria belonging mainly to the genus Clostridium ; by glycolysis, they can oxidize sugar, and occasionally amylose and pectin, to pyruvate.