One unique organism.

Flagella on bacteria.Pseudomonas aeruginosa is a very successful bacterium because of the many different types of adaptations it possesses. For starters, Pseudomonas aeruginosa is a free-living organism. Since this bacterium is free-living, its manner of locomotion is through a single polar flagellum. This flagella helps make it one of the fastest swimming bacteria known! Picture to the right is a bacteria with a single flagella- image from WikiCommons.

Another way that Pseudomonas aeruginosa has been able to adapt to its environment is through its ability to create a biofilm in environments where the bacterium is often exposed to liquid movement. A biofilm layer is considered an adaptation because it decreases an antibiotics’ ability to eradicate this bacterium in humans or other infected organisms. The formation of a biofilm layer is triggered because of cell-to-cell communication using a quorm sensing system. This system allows for the bacteria to communicate as a population/ group of cells. The cells’ ability to communicate with one another helps them to express their genes in coordination with one another and adapt more effectively to the particular environment they inhabit. In addition to the biofilm formation reducing the effectiveness of antibiotic treatment, the adaptations to the Pseudomonas aeruginosa’s cell membrane also help.

Below: Semi-permeable membrane from WikiCommons.
Bacteria have a semi-permeable membrane; only hydrophilic molecules can diffuse across the membrane. Whether or not an antibiotic is allowed to diffuse across the membrane of a bacterium is determined by the properties of the protein channels that line the outer membrane of the bacteria. These channels are what allow the movement of antibiotics and other molecules across the membrane. In order for antibiotics to work, they have to be allowed across the membrane into the cytoplasm. However, since Pseudomonas aeruginosa does not have a very highly permeable membrane, antibiotics have greater difficulty crossing the membrane to stop the bacterial infections they are meant to treat. Generally, the permeability of substances to a plasma membrane is determined by the types of channel proteins present in it and the overall pore size of the channels. However, in Pseudomonas aeruginosa pore size is very small compared to what is found in other bacteria making it a key factor in its resistance to antibiotics.
Although there are obvious advantages to having a membrane with low permeability to antibiotics, there are also costs involved. Low permeability is not restricted to just antibiotics, other materials that need to cross the plasma membrane also face restrictions. Useful materials like nutrients going into the cell and waste materials diffusing out of the cell are hindered by the same small pore sizes. But based on the success of Pseudomonas aeruginosa, its membrane clearly is providing a greater benefit than a limitation and has contributed to making it an extremely successful bacterium.  


Now let's check out what this bacterium needs in order to survive! (Nutrition)