A secretion is when something is released or oozes if you throw in the bacteria, you have a bacterial secretion. The easiest way to remember what a secretion is is to think of something being transported from the inside of a cell to the outside. There are many different things in the human body that secrete something. For example, the gastrointestinal tract secretes gastric acids and digestive enzymes and the sebaceous glands secrete a lubricating substance for hair and skin.
In order to explain and for you to understand what bacterial type VI secretion systems are, first an explanation on what gram negative bacteria is. A gram negative bacterium is a bacterium that will not be able to retain the crystal violet dye that laboratories use when they stain the cells put on a slide. In a gram stain test the crystal violet dye will be applied first, then a rinsing agent or counter stain agent is applied.
When the counter stain is applied the gram negative bacterium will not retain the stain and will appear red or pink in color. This is a test that would be used to diagnose illnesses like the flu, meningitis, and some sexually transmitted diseases. There are six different specialized secretion systems for gram negative bacteria. The sixth secretion system was only discovered in 2006 by a group at Harvard Medical School. The group was able to identify two bacterial pathogens, Pseudomonas aeruginosa, a bacteria and Vibrio cholera which causes cholera in humans.
The type VI secretions have been found in animals, humans, plants, soil, and in aquatic bacteria. It is very opportunistic and can be found just about anywhere, from your kitchen sink to a catheter in the hospital. The Pseudomonas aeruginosa is a very sneaky bacterium that has found a way to inject a toxin into any other rival bacteria, the P. aeruginosa uses its needle-like puncturing tool which is the T6SS to infect the rivals and kill them off.
One way to think of it is that the T6SS and other bacterium are playing king of the hill, but inside your body. Now do not go around thinking that at any moment you could be infected with P. aeruginosa, it most often targets people with lowered immune systems and thrives there. It has also been found that T6SS has developed immunities to such antibiotics as penicillin. This is a good reason to boost your immune system with healthy eating and exercise.
