Turbatrix aceti

The free-living nematode Panagrellus redivivus (common names include vinegar eel, vinegar eelworm, vinegar nematode, paste worm, starch worm, sour paste nematode, sour paste eelworm, beer felt nematode, and beer mat nematode), is a tiny nematode that can be found living in beer mats, insect frass, slime from tree wounds, wheat paste, and mother of vinegar. Their environment makes them exceptionally tolerant of variation in acidity and alkalinity and they may be able to tolerate a wider range than any other nematode species, being able to survive from pH 1.6 to 11. One of thirteen currently recognized species of Panagrellus, P. redivivus is about 50 μm in diameter and just over 1 mm in length, barely visible to the naked eye. Subsisting on yeast, it is easily cultured at home on a substrate of flour paste or porridge inoculated with dry yeast. Females reach maturity in about three days and deliver live young rather than eggs, as most nematodes produce. P. redivivus is known to many aquarium enthusiasts and fish keepers as the microworm. It is a tiny roundworm used as the first food for larger kinds of newly-hatched fish, such as larval common carp. The microworm is widely used in aquaculture as food for a variety of fish and crustacean species. The microworm has been used as a model organism in genetic analysis studies, but not nearly as universally as its relative, Caenorhabditis elegans. In Vietnamese cuisine, cơm mẻ is a ingredient appears in many dishes such as buffalo meat and fish soup thanks to its sourness. Cơm mẻ is the cooked rice being lactic fermented by yeast and maintained with the existence of P. redivivus. Although they are harmless and non-parasitic, leaving eelworms in vinegar is considered objectionable in the United States and is not permitted in vinegar destined for American consumers. Manufacturers normally filter and pasteurize their product prior to bottling, destroying the live bacterial and yeast culture that these nematodes require for sustenance.