The basic objective in this method is to demonstrate the presence or absence of bacteria that ferment the sugar lactose added to a nutrient liquid medium and produce gas within a specified period of 48 hours. Which method is described?

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Detecting lactose fermentation with gas production in a liquid medium is achieved with the Multiple Tubes technique. In this approach, a series of tubes containing lactose in broth are inoculated, and each tube includes a small Durham tube to trap any gas produced. If the bacteria ferment lactose and generate gas within the 48-hour window, the gas lifts the liquid in the Durham tube, producing a visible positive result. The use of multiple tubes (often at different dilutions) allows you to determine presence or absence of lactose-fermenting organisms and gives a sense of their concentration.

Plate Cultures would show colonies on solid media rather than gas production in a closed tube; Turbidity Measurement tracks overall growth but not gas formation; Microscopy looks at cells rather than fermentation outcomes.