The methods of bacterial growth measurement

The methods of bacterial growth measurement

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  METHODS OF BACTERIALGROWTH MEASUREMENT DEPARTMENT OF VETERINARY MICROBIOLOGY PRESENTED BY :- DR. PUSHPENDRA BAGHEL ROLL NO. :- M-6470
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  METHODS FOR BACTERIALGROWTH MEASUREMENT  In Microbiology, Growth is defined as a process of – Increase in number of microorganisms by Asexual method OR Increase in cell mass OR Increase in cell activity. ( Here, growth refers to population growth, rather than growth of individual cells.)
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  MEASURMENT OF BACTERIALGROWTH 1. DETERMINATION OF CELL MASS. 2. DETERMINATION OF CELL ACTIVITY. 3. DETERMINATION OF CELL NUMBER.
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  CELL MASS DIRECT METHOD PHYSICAL DRY WEIGHT WET WEIGHT CHEMICAL MEASURMENT OF CELLULAR COMPONENT INDIRECT METHOD METABOLIC ACTIVITY RATEOF PRODUCTION OF METABOLIC PRODUCT TURBIDITY SPECTRO- PHOTOMETER
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  DRY WEIGHT ANALYSIS In this method, at first, the sample is centrifuged  Than the resulting cell pellet is filtered and then it is weighed. ADVANTAGES:  It is a easy and rapid method.  It is the only way to determine growth of filamentous bacteria. DISADVANTAGES:  Cumbersome and not very accurate.  Does not give distinction between cell number and cell mass.  It cannot distinguish between live and dead cells.
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  MESURMENT OF CELLNITROGEN  As the microbes (bacteria) grow, there is an increase in the protein concentration (i.e. nitrogen concentration) in the cell.  Around 14% dry weight of bacterial cell is nitrogen.  Thus, cell mass can be subjected to quantitative chemical analysis methods to determine total nitrogen that can be correlated to growth.  This method is useful in determining the effect of nutrients or antimetabolites upon the protein synthesis of growing culture. LIMITATIONS:  It can be performed only on samples free from all other sources of nitrogen.  It is applicable for concentrated solutions only.
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  MEASURMENT OF METABOLICACTIVITY  Another Indirect method of estimating bacterial mass is measuring the metabolic activity of the population ( for example – acid production or oxygen consumption, nutrient utilization, waste production, pH etc).  The assumption is that the amount of acid produced or oxygen consumed under specific conditions and during a fixed period of time is proportional to the magnitude of bacterial populations.  Admittedly, the measurement of acid or any other end product is a very indirect approach to the measurement of growth and is applicable only in special circumstances.
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  TURBIDOMETRIC METHOD  Rapidcell mass determination is possible using Turbidometry method.  Turbidometry is based on the fact that microbial cells scatter light striking them.  Since the microbial cells in a population are of roughly constant size, the amount of scattering is directly proportional to the biomass of cells present and indirectly relates to cell number.  One visible characteristic of growing bacterial culture is the increase in cloudiness of the medium (turbidity).  A Spectrophotometer is used to determine turbidity by measuring the amount of light that passed through a suspension of cells.  More cells = More turbidity; More turbidity = Less light passing through the suspension.  However, the culture to be measured must be dense enough to register some turbidity on the instrument.
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   LIMITATIONS:  Itdoesn’t give the value of cell mass but the number has to be calculated by plotting calibration curve between mass and optical density.
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  TURBIDOMETRIC METHOD