Isolated thunderstorms are when there are either thunderstorms present at the current time or there is a change for them to form, but they are scattered. These usually occur in the afternoon and the evening when the sun is out at its peak and heats up the atmoshpere.
For example, bacteria from the genus Salmonella are mostly facultative anaerobes, oxidase-negative, catalase-positive and gramnegative rods. Most strains are motile and ferment glucose with production of both acid and gas.
By eliminating lactose, these organisms will produce an abundance of hydrogen sulfide in the medium and may be detected. The incorporation of lysine is another important addition, as most species of Salmonella produce the lysine decarboxylase enzyme. Proteus and Providencia species also may be presumptively identified on this medium, as they produce a red slant and an alkaline butt. The indicator in LIA is bromcresol purple.