Light scattering is proportional to the number of bacteria per ml, and by means of a standard curve, one can determine the number of bacteria in absolute terms. of bacteria) light scattering (OD = optical density) can also be measured. With a spectrophotometer you normally determine absorbance at different wavelengths, but in a suspension (e.g. The fastest and easiest method is to regularly collect samples from the culture and determine light scattering by spectrophotometry. addition of a substance, or when cultivation should be interrupted. However, the DNA replication process itself is different. So binary fission is the way in which bacteria reproduces and similar to my toe sis DNA replicates. When a growth curve is constructed, you most often want to be able to follow the growth of bacteria in real time to know when to make e.g. Okay, So lets look at Via Neri fission and my toe sis, and how the two are similar and different. Later, the exchange of cytoplasmic material occurs. A septum begins to form between the cell, which constricts the cell into two. Then, the cell elongates, and the DNA is copied. and includes the following steps: First, the parent cell duplicates its DNA from the origin of replication. During the stationary phase bacteria die at about the same rate as they are formed during cell divisions, and in the death phase, bacteria die faster than they regenerate. Binary fission is common in prokaryotes like bacteria, archaea and eubacteria etc. Note that the scale of the y axis is logaritmic. paratuberculosis cannot be observed until after at least 3 months! Growth curveīacterial growth can be described by a so-called growth curve with four different phases: lag phase, log phase, stationary phase and death phase (= decline phase) (labelled A, B, C and D, respectively, in the figure).
This means in practice that if you spread these two bacteria on appropriate culture plates, you can easily see colonies of E.
paratuberculosis has a generation time of about 24 hours. Escherichia coli, which is cultivated under optimum conditions, has a generation time of 20 min, whereas Mycobacterium avium subsp. The time required for the number of bacteria to double during cultivation is called generation time or doubling time and it can vary greatly for different bacteria. When a bacterial culture is initiated in a liquid medium, it takes some time before the bacteria will start to grow, especially from clinical specimens or from hypothermic cultures and this phase of cultivation is known as the lag phase. The exponential growth phase ( log phase) can not continue indefinitely, because the culture medium will become depleted of nutrients and the pH of the medium usually changes.
If the availability of nutrient is constant, and the physico-chemical properties of the culture medium does not change, they divide by the same speed all the time. Bacteria multiply by binary fission (two identical daughter cells are formed upon the cell division).
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