MICROBIAL GROWTH CURVE PART ONE- A SIMPLE INTRODUCTION

How do we define microbial growth? To most people when we talk about growth we are always talking about the progression in the development of the organism as a function of time. The progression of growth of the organism or the individual is usually associated with increase in size or biomass of the organism.
The key point here is the INDIVIDUAL organism. However in dealing with microorganisms, most microbiologists tend to picture microbial growth from the view point of the increase in the total population of microorganisms and not the individual unicellular microorganism
The growth of the microbial population at any one time represents the steady state number of cells or growth parameters used as the index of growth. The steady state numbers represent the net number of cells where input of cells and death or loss of cells are taken into considerations
The growth of the cells over time is often conveniently represented in graphs.
These microbial growth curves therefore represent the growth of microbial population rather than the individual cell. So any information derived from studying the growth curve represent understanding the behavior of the population rather than the individual cell.
The behavior of the individual cell differs from the behavior of the population of cells. This must always be bear in mind all the time in interpreting growth curves.
It is one of the weakest link in understanding the behavior of the microbial population to regard it as a simple integration of the activities of the individual cell. This is microbial physiology and not plain mathematics! Everything is not averages or mean values!
It is a gross error or over simplification to regard the microbial growth curve is the popular sigmoid shaped growth curve. In fermentation technology the type of growth curve obtained are determined by many factors and operating regimes. Yet time and time again the error of interpreting the wrong growth curves are continually repeated.


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