Microbiology (Lab Report)
Bacterial growth curve
Lab Report
Bacteria are prokaryotic organisms that replicate by an asexual process of binary fission. The microbes reproduce at a higher rate under favorable conditions. The growth is represented in a pattern of growth which geographically represents some living cells in a population over time. This pattern is known as a bacterial growth curve. Consequently, the growth circles entail of four phase lag, exponential stationery, and death.
Besides, the growth rate of bacteria’s is exponential which in the laboratory growing bacterial doubles at favorable conditions. Bacteria were raised in a closed system shown a specific growth pattern which consisted of four phases namely; the lag phase which relates to a period of maximum growth — secondly, the exponential growth phase, where growth in this phase is quite balanced. Thirdly, the stationary phase in which nutrients become the limiting factor making the growth rate equal to death rate — lastly, the death phase where organisms die faster than they are replaced.
It is of more advantage to know how fast a microbe grows to know bactericidal or antibiotic concentrations. Furthermore, when evaluating a growth curve gives one a perspective of the generation time and the mean growth of the bacterium.
The distinct phases that the Bacterium undergoes in the closed system curve;
Lag phase
The bacterium undergoes through a period of acclimatization after it has been inoculated into the sterile nutrient medium. During this time the e3nzymes and intermediate metabolites continue to be synthesized. Due to this, the bacterium reaches a critical stage before multiplication. In this stage, multiplication occurs. Several factors lead to the duration of the lag phase. For instance the type of bacteria, quality of culture medium, several environmental factors such as CO2 temperature pH among others.
Exponential Phase
During this phase, the bacteria undergo cell division in their population. Consequently, they increase exponentially at a logarithmic rate. This is well illustrated in figure 7.4 and 7.5 where the log of the number of cells plotted against time results in a straight line. As a result, under appropriate conditions, the growth rate is maximal during the phase. Also important to note the cells in the exponential phase of growth are the healthiest and most uniform. This explains why most experiments utilize cells from this phase.
Stationary phase
In this phase, the growth begins to taper off several hours. Consequently, it is represented by the transition from a straight line through a curve as illustrated in figure 7.5. The cell division ceases due to exhaustion of nutrients and also the accumulation of toxic products. Similarly, cell death begins slowly and is compensated by the formation of a new cell through the process of cell division. Physiologically the cells become entirely different at this stage, as they try to adapt to their new starvation conditions. Consequently, the few new cells that are produced are smaller in size, with bacilli becoming almost spherical.
The total number of cells increases at a slow rate whereas the viable remains constant. The period of this phase ranges from a few hours and a few days. Also to note, in this phase antibiotics, toxins are produced which are secondary metabolites.
Decline phase
The population remains constant for some time. Consequently, the viable cells gradually decrease due to exhaustion of nutrients and also due to the accumulation of toxic products. Some conditions contribute to bacterial death. The most important include the depletion of essential nutrients.
Also, another factor is the accumulation of inhibitory products for example acids. Furthermore, during the death phase decreases exponentially. Again to note bacterium die at different rates just as they grow at different rates. Also, other species die so slowly that viable cells may persist for months or even years.
In summary, the death phase is an inverse of the log phase. The difference is that the death rate is slower than the growth rate. Not all bacteria die at the same rate; some die faster. On the other hand, some are more resistant and remain viable for a longer time, for instance, Spore-forming bacteria.
CONCLUSION
In summary, at a temperature over one the density of the organism increased with time. Similarly, before the stationary phase to show that the bacterial had adjusted and continued using the nutrients to develop and increase. As a result, this leads to an increase in cell density and the number of variable cells. Consequently, from the graphs, we realize that they differ because with time cell growth continues to increases. Again, the graph of time illustrates how variables cells increases.