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One of the primary functions of using PLFA analysis at contaminated sites is to evaluate how a community responds following a given treatment. How does one know if the changes observed between two events are significant? As a general rule, biomass levels which increase or decrease by at least an order of magnitude are considered to be significant. However, changes in biomass levels of less than an order of magnitude may still show a trend. It is important to remember that many factors can affect microbial growth, so factors other than the treatment could be influencing the changes observed between sampling events. Some of the factors to consider are: temperature, moisture, pH, etc. The following illustration depicts three types of changes that occurred over time and the conclusions that could be drawn.
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Conclusions from above graph:
- MW-1 showed a trend of biomass levels increasing steadily over time, although cell concentrations were ~10e4 cells/mL at each event.
- MW-2 showed no notable trends or significant changes in biomass concentrations.
- MW-3 showed a significant increase in biomass levels between the initial and 1st qtr sampling events (from ~10e5 to ~10e6 cells/mL)
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