|
Abstract
|
Lactobacillus plantarum is a widespread member of the genus Lactobacillus, commonly found in many fermented food products as well as anaerobic plant matter. It is also present in saliva (from which it was first isolated). It has the ability to liquefy gelatin. L. plantarum has one of the largest genomes known among the lactic acid bacteria and is a very flexible and versatile species.L. plantarum is a Gram-positive-aerotolerant bacteria that grows at 15 °C (59 °F) but not at 45 °C (113 °F), and produces both isomers of lactic acid (D and L). This species and related lactobacilli are unusual in that they can respire oxygen but have no respiratory chain or cytochromes[citation needed] — the consumed oxygen ultimately ends up as hydrogen peroxide. The peroxide, it is presumed, acts as a weapon to exclude competing bacteria from the food source. In place of the protective enzyme superoxide dismutase present in almost all other oxygen-tolerant cells, this organism accumulates millimolar quantities of manganese polyphosphate. Manganese is also used by L. plantarum in a pseudo-catalase to lower reactive oxygen levels. Because the chemistry by which manganese complexes protect the cells from oxygen damage is subverted by iron, these cells contain virtually no iron atoms; in contrast, a cell of Escherichia coli of comparable volume contains over one-million iron atoms. Because of this, L. plantarum cannot be used to create active enzymes that require a heme complex such as true catalases.
|