This basic batch culture growth model draws out and emphasizes aspects of bacterial growth which may differ from the growth of macrofauna. At death phase, bacteria run out of nutrients and die. Death of cells as a function of time is rather unpredictable and very difficult to explain. Finally, the stationary phase is due to a growth-limiting factor, such as depletion of a nutrient and/or the formation of inhibitory products such as organic acids. However, exponential growth cannot continue indefinitely because the medium is soon depleted of nutrients and enriched with wastes. the slope of the line in the figure) depends upon the growth conditions, which affect the frequency of cell division events and the probability of both daughter cells surviving. The slope of this line is the specific growth rate of the organism, which is a measure of the number of divisions per cell per unit time. For this type of exponential growth, plotting the natural logarithm of cell number against time produces a straight line. If growth is not limited, doubling will continue at a constant rate so both the number of cells and the rate of population increase doubles with each consecutive time period. The number of new bacteria appearing per unit time is proportional to the present population. The exponential phase (sometimes called the log phase or the logarithmic phase) is a period characterized by cell doubling. During this phase of the bacterial growth cycle, synthesis of RNA, enzymes, and other molecules occurs. It is the period where the individual bacteria are maturing and not yet able to divide. The phases of growth are labelled on top.ĭuring lag phase, bacteria adapt themselves to growth conditions. Note the Y-axis scale is logarithmic meaning that the number represents doubling. Figure: Bacterial Growth Curve: This chart shows the logarithmic growth of bacteria. In autecological studies, bacterial growth in batch culture can be modeled with four different phases: lag phase, exponential or log phase, stationary phase, and death phase. ![]() The basic means requires bacterial enumeration (cell counting) by direct and individual (microscopic, flow cytometry), direct and bulk (biomass), indirect and individual (colony counting), or indirect and bulk (most probable number, turbidity, nutrient uptake) methods. The measurement of an exponential bacterial growth curve in batch culture was traditionally a part of the training of all microbiologists. If the number surviving exceeds unity on average, the bacterial population undergoes exponential growth. The doubling time is the generation time of the bacteria. Both daughter cells from the division do not necessarily survive. Therefore, “local doubling” of the bacterial population occurs. Providing no mutational event occurs the resulting daughter cells are genetically identical to the original cell. \)īacterial growth is the division of one bacterium into two daughter cells in a process called binary fission.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |