Coloured transmission electron micrograph (TEM) showing a Lactococcus lactis bacterium. It belongs to the Streptococcus genus and is usually arranged in chains formed by several bacteria. Lactococcus lactis is one of the bacteria involved in the production of lactic acid during milk fermentation. Lactic acid is a colourless liquid which occurs in yoghurt. buttermilk, sour cream and also in poor wine. Lactococcus lactis has a diameter of approximately 1 micrometer; the green areas within the bacterium show regions where the nucleic material (DNA) is found. Magnification: x23,000 at 6x4.5cm size.