Strategies to Prevent Bacterial Adhesion on Biomaterials - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 167

One of the important characteristics of bacteria is their generation time
(G) , the doubling time for a prokaryotic population. In general, G is dif-
ferent for different types of microbials and most of the bacteria have the
generation time of approximately 30 minutes to three hours [37]. Certain
bacteria, for example, Escherichia coli, have very short generation times of
20 mins under optimal conditions. The bacterial population follow the
exponential growth curve. The generation time of the cells can be calcu-
lated by the following formula:

G = t/2.3log (b/B) (7.1)

Where G is generation time, t is culture time, B is number of cells at the
beginning of culture and b is number of cells at the end of culture [23].

7.2.2 Bacterial Growth Behavior In Vitro

The bacterial growth curve is comprised of four phases known as lag
phase, log phase, stationary phase and, fi nally, death phase [23]. The char-
acteristic growth curve is shown in Figure 7.8, where logarithms of the
actual numbers in the population are plotted along the Y − axis and the

incubation time is plotted along the X axis.

In the lag phase , the population remains constant and no cell division
occurs [24]. When cells are transferred into the new culture medium they
take some time in physiological adaptation rather than directly going into
the division phase. After the lag phase of growth curve, cells come into
the log phase during which binary fi ssion occurs, and this corresponds
to the exponential growth of bacteria up to the optimal level. During the
next phase, i.e., the stationary phase , cells stop division, but do not start
dying, and the number of cells remains constant. The last phase is the

−

Stationary
phase

Death/decline
phase

Lag
phase

Time in growth medium

Figure 7.8 Typical illustration of growth behavior of bacteria in growth medium
in vitro (adapted from ref. [24]).