Biology - Microbiology - Essay Example

Download file to see previous pages It is therefore essential to understand the microbes linked with the commodities we use in our everyday life. Microorganism vary widely in morphology displaying spherical, rod like or spiral shapes. One of the significant feature that is universal despite their appearances is they divide through binary fission. The cell grows to twice its size, DNA, the genetic material replicates and then the cell divides into two like cells which share the same genotype as the parent cell. The two newly formed cells are called the daughter cells as they receive one copy of each replicated DNA. Since the two daughter cells are genetically similar they are referred as clones. Cells descending from the parent cell form a mass of cells on the solid surface, agar plates and are known as colony. The colony is derived from a single cell and this is referred as colony forming unit (CFU) (Stanier, 1986). The cell divides into two new cells and then these two cells give rise to four new cells which eventually divides to form eight cells establishing a mathematical series called 1, 2, 4, 8, 16, 32, 64,... which can be expressed as 20, 21, 22, 23, 24,...with a base of 2. Such series is called the exponential series and the growth curve obtained displaying bacterial growth is called exponential growth curve highlighting the fact that bacterial population increases rapidly and possess short generation time equivalent to 30 minutes. With such a rapid pace of cell division the population of bacteria grows two fold in one hour and 16 fold in mere two hours. If the trend continues the population may attain trillion fold, but there is a check mechanism that limits the bacterial growth. Thus, instead of a constant steady rise in the population of bacterial cells, the bacterial growth curve displays four phases- A. The lag phase- It is the primary phase after the bacterial cells are inoculated in the growth medium. In this phase the bacterial cells do not divide, instead they prepare themselves with high metabolic rate for the cell division. If the nutrients are sufficient to support the growth and cellular requirements, the lag phase may be short. If the medium of inoculation is poor in nutrient requirement of the cell the time taken by the cells to prepare themselves to onset cell division, the cells are required to produce amino acids and vitamins, the bacterial growth displays long lag phase; as after active metabolism only the cells begin DNA replication. This is a preparatory step for the second phase of growth (Stanier, 1986). B. The log or the exponential phase of growth- In this phase the cells display rapid cell division. The time taken by the cells to produce daughter cells is regarded as the generation time. This phase is depicted as the steep rise in the bacterial growth. The generation time could be calculated by pointing two points on the straight line and calculating the time required to attain the same. However, the generation time depends on various factors encompassing the organism, the growth medium as well the given temperature. Thus generation time varies between different bacterial species. Estimations reveal that fastest growing organisms have generation time of 15- 20 min under optimal growth provisions (Stanier, 1986). C. The stationary phase- in this phase the metabolism slows down and cells cease rapid cell division. Cells display declining metabolism as well as the rapid pace of cell division also reduces. Stationary phase is initiated by the altered ...Download file to see next pagesRead More