The drops formed from a single gas bubble bursting at a liquid‐gas interface were used as a technique to sample the surface microlayers, and concentration factors for the drops were determined for the marine bacterium Serratia marinorubra. These factors, varying between 2 and 100, depended on the bulk densities of the bacteria. A model is presented that relates bacterial bulk densities to bacterial densities in a microlayer at the surface. Preliminary experiments with natural seawater populations revealed that concentration factors were markedly higher than those for S. marinorubra.