In 1907, Japanese researcher Kikunae Ikeda of the Tokyo Imperial University identified brown crystals left behind after the evaporation of a large amount of kombu broth as glutamic acid. These crystals, when tasted, reproduced the ineffable but undeniable flavor detected in many foods, especially seaweed. Professor Ikeda coined the term umami for this flavor. He then patented a method of mass-producing the crystalline salt of glutamic acid known as monosodium glutamate. Isomers
Further research into the compound has found that only the L-glutamate enantiomer has flavor-enhancing properties. Manufactured monosodium glutamate consists to over 99.6% of the naturally predominant L-glutamate form, which is a higher proportion of L-glutamate than can be found in the free glutamate ions of fermented naturally occurring foods. Fermented products such as soy sauce, steak sauce, and Worcestershire sauce have levels of glutamate similar to those in foods with added monosodium glutamate. However, 5% or more of the glutamate may be the D-enantiomer. Nonfermented naturally occurring foods have lower relative levels of D-glutamate than fermented products do. Taste perception
Glutamic acid stimulates specific receptors located in taste buds such as the amino acid receptor T1R1/T1R3 or other glutamate receptors like the metabotropic receptors (mGluR4 and mGluR1), which induce the flavor known as umami. This is classified as one of the five basic tastes (the word "umami" is a loanword from Japanese; it is also referred to as "savory" or "meaty"). The flavoring effect of glutamate comes from its free form, in which it is not bound to other amino acids in protein.
This is in part due to the large variety of organisms living in the urinary tract. Ureaplasma urealyticum and Mycoplasma genitalium are some of the culprits. NGU is also associated with reactive arthritis, in which the triad of arthritis, conjunctivitis, and urethritis is seen. Bacterial
The most common bacterial cause of NGU is Chlamydia trachomatis, but it can also be caused by Ureaplasma urealyticum, Haemophilus vaginalis, Mycoplasma genitalium, Mycoplasma hominis, Neisseria meningitidis, Gardnerella vaginalis, Acinetobacter lwoffii, Acinetobacter calcoaceticus,  and E.coli. Viral
Herpes simplex virus, Adenovirus,
Cytomegalovirus

Fungi
Candida Albicans

Parasitic
Parasitic causes include Trichomonas vaginalis (rare). Noninfectious
Urethritis can be caused by mechanical injury (from a urinary catheter or a cystoscope), or by an irritating chemical (antiseptics or some spermicides). Diagnosis
It has been easy to test for the presence of gonorrhea by viewing a Gram stain of the urethral discharge under a microscope: The causative organism is distinctive in appearance; however, this works only with men because other non-pathogenic gram-negative microbes are present as normal flora of the vagina in women. Thus, one of the major causes of urethritis can be identified (in men) by a simple common test, and the distinction between gonococcal and non-gonococcal urethritis arose for this reason. Non-gonococcal urethritis (NGU) is diagnosed if a person with urethritis has no signs of gonorrhea bacteria on laboratory tests. The most frequent cause of NGU (23%-55% of cases) is C. trachomatis.