It has become a common practice to test the quality of water using the filter method we learned about in this chapter. This is especially true for water sources that have public access. The potential for fecal contamination of water is greatest in these places. The testing gives us the coliform count which is a measure of how much fecal contamination is present. If the number is high enough it presents a health hazard and access to the water must be restricted.
Different bacteria have different growth rates. In the case of pathogens, the growth rate is important because the number organisms present is usually directly related to the seriousness the infection. In the case of treatment, it can depend on what type of organism you are dealing with. If the pathogen is Gram-positive and is growing rapidly, antibiotics that attack the cell wall can be very effective for treatment. The higher the rate of cell wall production, the better these drugs will work. If the organism is growing slowly, antibiotics targeting of the cell wall may be ineffective. This relationship of rapid growth leading to increased sensitivity to antibiotics is also true for Gram-negative pathogens, even though they are less sensitive to penicillin type antibiotics in general.
The obligate anaerobe is an organism that cannot grow in the presence of oxygen. In contrast, the facultative organism can grow with or without oxygen. Facultative organisms prefer oxygen because it can produce more ATP when growing in the presence of oxygen.