Bacterial Population Growth

 

Most bacteria reproduce by a process called binary fission, during which the cell duplicates its
components and divides into two cells. Under favorable conditions, individual bacteria rapidly
proliferate, forming macroscopically visible colonies (or clones) consisting of millions of genetically
identical cells on the surface of an agar plate or turbidity representing millions to billions of cells per
mL in a broth solution.
The growth of bacterial populations progresses through four phases: lag phase, exponential (log)
phase, stationary phase, and death phase (Figure 1). The student must remember that these growth
phases refer to a bacterial population, not to individual cells. Individual cells may or may not be
following the overall growth pattern of the population at any one time. For example, in the
stationary phase, the population is in a “leveling off” phase; however, many cells are still actively
growing and metabolizing.
Lag phase
The lag phase is the period where a population is adapting to its environment. It is sensing what
nutrients are available and producing the enzymes necessary to extract energy and divide during the
next phase. There is no growth in number of cells during this phase.
Log or exponential phase
The log or exponential phase is the term used to describe the pattern of population growth in which
the number of cells doubles during each unit time. One of the characteristics of exponential growth
is that the rate of increase in cell numbers is slow during the initial stages but increases at an everfaster rate. During the later stages of growth, this results in an explosive increase in cell population
numbers. Mathematically, this is known as exponential growth. The log growth phase is used to
calculate generation time and it’s the time it takes for a population to double. When the log of the
number of cells is plotted over time, there will be a linear increase in this phase.
Stationary phase
The stationary phase is the period immediately after the log phase. The cells are beginning to
exhaust the available nutrients, and waste products are beginning to accumulate. There is no net
growth; the number of dying cells is equal to the number of reproducing cells.

 

Sample Solution

Bacterial growth occurs when a bacterium divides into two daughter cells, a process known as binary fission. If nothing happens, the daughter cells will be genetically identical to the original cell. As a result, bacterial proliferation takes place. The division’s two daughter cells do not always survive. The bacterial population, on the other hand, grows exponentially if the number of survivors exceeds unity on average. The measurement of an exponential bacterial growth curve in batch culture was traditionally a part of all microbiologists’ training; the basic means requires bacterial enumeration (cell counting) by direct and individual (microscopic, flow cytometry, direct and bulk (microscopy, flow cytometry, direct and bulk (microscopy, flow cytometry[1]), direct and bulk (microscopy, flow cytometry, direct and bulk (microscopy (biomass),

ere are other contingency theories that provide a more continuum based approach such as Redding’s theory of leadership and management, however Fielder’s description of how situational factors affect the leadership style required for the situation is extremely useful in understanding the fundamentals of leadership (Pettinger, 2007). Chelladurai in his Multi Dimensional Model of Leadership, expands on much of Fiedler’s theory but in a continuum based approach, in which the leader can adapt their leadership style to fit the situation (Chelladurai and Madella, 2006). Chelladurai’s theory is taken from sports psychology but can be applied to an organisational scenario. It provides a much more empirical categorisation of task structure, clearly differentiating a plethora of situations that require certain leadership styles for success. Chealldurai found three characteristics that affect the leadership style required for a situation, called antecedents, they mainly expand upon Fiedler’s situational factors and leader – member relations and ultimately affect how a leader should behave towards a situation. The first are situational characteristics, the environment in which the leader must perform, the second are leader characteristics, the experience, personal qualities and skills of the leader, and the third are member characteristics, the motivation, skill and experience levels of group members (Chelladurai and Madella, 2006). The situational characteristics and member characteristics have a required behaviour to ensure maximum group performance, they also have a preferred behaviour to ensure the satisfaction of group members, if the leaders actual behaviour matches both the required behaviour and preferred behaviour of the situation the consequence is maximum group performance and satisfaction. However, if the group are not performing and achieving goals or are not satisfied or both, then the leader is able to amend their actual behaviour to improve this. Leaders able to monitor performance and satisfaction, and understand what is required to amend the situation will achieve optimum group performance in Chelladurai’s model. The one limitation of Chealldurai’s model is that it assumes the leader is in a position of complete positional power over the group, and can implement any leadership style of their choosing without constraints. Positional power is the authority and influence a leader has over a group, if the leader has positional power, they will be able to implement the leadership style they best see fit for the situation. Positional power cannot be measured or quantified, making it highly ambiguous and hard for a leader to understand whether they have it or how then can gain it. It becomes the responsibility of the organisation to have policies in place to provide leaders with some positional power, usually by establishing a clear hierarchal structure. By establishing a hierarchy, the leader is perceived by the group to be able to make demands and expect compliance

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