what organ contains bacteria that help produce vitamin k
The large intestine
Vitamin K
Many bacteria, including "Escherichia coli" found in the large intestine, can synthesize vitamin K (MK-7 up to MK-11), but not vitamin K. 
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Vitamin K [SEP] Function in bacteria
Many bacteria, including "Escherichia coli" found in the large intestine, can synthesize vitamin K (MK-7 up to MK-11), but not vitamin K. Green algae and some species of cyanobacteria (sometimes referred to as blue-green algae) are able to synthesize vitamin K. In the vitamin K synthesizing bacteria, menaquinone transfers two electrons between two different small molecules, during oxygen-independent metabolic energy production processes (anaerobic respiration). For example, a small molecule with an excess of electrons (also called an electron donor) such as lactate, formate, or NADH, with the help of an enzyme, passes two electrons to menaquinone. The menaquinone, with the help of another enzyme, then transfers these two electrons to a suitable oxidant, such as fumarate or nitrate (also called an electron acceptor).