Microbial Growth Curve - Term Paper Example

? "Microbiology" Microbial Growth Curve Microbes are indispensible module of our environment. They are associated in a variety of ways with everything we use in our everyday lives. They are found to be associated with the food that we eat, the clothes we wear/make use of and water we drink/utilize. They may perhaps influence the quality of our lives. Food items may be contaminated during the handling process, surroundings and the sanitary conditions where they are kept. Food and water may also carry pathogenic microbes and as a result transmit disease. 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 environmental conditions as well as high cellular density, depleted nutrition as well as accretion of waste products. As soon as cells from the stationary phase are transferred to the fresh medium the exponential growth phase is resumed (Stanier, 1986). D. The death phase- this is the final phase of the growth cycle. If cells from this stage are transferred to the fresh nutrient medium they are unable to divide. The death phase is also exponential and cells die quickly and a stage is reached where the culture may not have any living cell. In order to preserve the cells in the viable condition the cells must be preserved in the chilled condition at the early stages of the stationary phase (Stanier, 1986). (Bacterial growth curve) Nutrient factors Nutrition is the process through which organisms obtain chemical substances called nutrients. These nutrients are used in cellular activities such as metabolism and growth. Different organisms utilize diverse resources of elements in their particular chemical form to procure nutrients. These nutrients aid in growth of the microorganisms both in size and number of organisms of a given population. As cellular process require varied variety of elements so the microorganisms also require different elements encompassing C, H, O, P, K, N, S, Ca, Fe, Na, Cl, Mg. However the percentage varies from species to species depending upon the characteristic of the organism. Based on the importance of nutrient being utilized by the organism they are categorized as- Essential Nutrient- that must be provided for the growth, development and survival of the microorganism. If this is required in large amount as it plays an imperative role in metabolism of the organism it is called macronutrient such as Carbon, hydrogen and oxygen. On the other hand if the nutrients are required in small amounts but are essential for the function of important enzyme and also for the formation of structural cellular components and maintenance of protein structure such as manganese, zinc and nickel they are called micronutrients (Pelczar, 1993). Role played by different organic as well as inorganic nutrients- carbon, hydrogen and oxygen atoms which are essential for carbohydrate molecules, lipids. Besides this nitrogen and sulfur are essential for amino acids and nucleic acids. Nucleic acids also require phosphate molecules, they play vital role in the formation of genetic material (DNA and RNA molecules) and also for ATP. Cofactors of enzymes and also vitamins require potassium, magnesium, calcium and iron (Pelczar, 1993). Microorganism in food spoilage system Food spoilage is the result of microbial activity as microbes are ubiquitous. Food items rich in proteins such as meat, poultry and dairy products are susceptible to microbial attack while fruits and vegetables are also attacked by the microbes. Pathogenic microbes such as Salmonella or E coli often deteriorate the food products resulting in the food spoilage and form slimy surface and also cause discoloration of food items. Consumption of such contaminated food items cause food-borne illness as well as food spoilage (Food Poisoning and Food Spoilage). Attack by Clostridium botulinum results in botulism which is health hazardous and may even lead to death. Microbes such as Pseudomonas also cause rancidity of milk. Canned food are also spoiled by gas producing organisms belonging to the genus Clostridium and Bacillus resulting in flat- sour spoilage while acid spoilage is caused by Lactobacilli (Food Spoilage). (Clostridium botulinum) Microorganism in an industrial manufacturing system Microorganisms play vital role in industries highlighting the fact that microbes are not only deleterious but play role in the economical development. Microorganisms are important for the field of biotechnology. Bacteria, fungi and algae are vital for industrial manufacturing of various products. Fermentation process encompassing cheese manufacturing, bakery products, dairy products, vinegar and wine manufacturing, pickle making involve microbes like Lactobacilli, yeasts and some strains of molds. Other industrial products involving organic acid manufacturing as well as for the formation of perfumes require microbial intervention for purity. Genetic engineering exploits microbes for manufacturing human hormones, insulin, antibodies by utilizing recombinant DNA technology. Microbes such as Escherichia coli is also used in vitamin synthesis and for making vitamin supplements. Besides these fiber retting industry use microbial action of Clostridium butyclicum for separation of fibers to make various products of jute and flax (Okafor, 2007). (Lactobacillus) Microorganisms in an environmentally important system Microbes play vital role in microbial biodegradation or bioremediation of varied kinds of wastes produce in nature and much more due to human activities in the present epoch. Various kinds of pollutants are treated by the microbial action encompassing pesticides, oil spillage, industrial effluent, waste water treatment. These treatments are being performed in bioreactors. Nitrogen fixation is performed by Rhizobium present in root nodules of legumes. Some microbes act as sensors of stress e.g. Lichens are sensitive to air pollution and therefore used by environmental scientists to understand environmental disturbances (Maier, 2000). (Lichen: Alectoria imshaugii) References Bacterial growth curve. [electronic print] Available at: [Accessed 26 May 2012]. Clostridium botulinum. [electronic print] Available at: [Accessed 26 May 2012]. Food Poisoning and Food Spoilage. [online] Available at: [Accessed 26 May 2012]. Food Spoilage. [online] Available at: [Accessed 26 May 2012]. Lactobacillus. [electronic print] Available at : [Accessed 26 May 2012]. Lichen: Alectoria imshaugii. [electronic print] Available at: [Accessed 26 May 2012]. Maier, R.M., Pepper, I.L., Gerba, C. P., 2000. Environmental Microbiology. Academic Press. Okafor, N., 2007. Modern Industrial Microbiology and Biotechnology. Science Publishers. Pelczar, M.J., 1993. Microbiology: Concepts and Applications. Study Gd ed. Mcgraw-Hill College. Stanier, R.Y., Ingraham, J.L., Wheelis, M.L., Painter, P.R., 1986. The Microbial World. 5 Sub ed. Prentice hall College Div.Nutrition is a process by which organisms acquirechemical substances (Nutrients) used in cellularactivities such as metabolism and growth.Organisms differ in the use of particular elements,their source and chemical form. Microbial growth Microbial growth refers to both the increase in cellsize and number of cells in a population Nutrition is a process by which organisms acquirechemical substances (Nutrients) used in cellularactivities such as metabolism and growth.Organisms differ in the use of particular elements,their source and chemical form. Microbial growth Microbial growth refers to both the increase in cellsize and number of cells in a population Nutrition is a process by which organisms acquirechemical substances (Nutrients) used in cellularactivities such as metabolism and growth.Organisms differ in the use of particular elements,their source and chemical form. Microbial growth Microbial growth refers to both the increase in cellsize and number of cells in a population Read More