Rifampin as a selective agent for the enumeration and isolation of spirochetes from salt marsh habitats

Spirochetes from a variety of salt marsh sediments were enumerated and isolated directly by using a prereduced complex medium containing rifampin as a selective agent. Based on cell morphology, the spirochetal strains isolated were divided into two groups, a group consisting of tightly coiled spirochetes and a group consisting of loosely coiled spirochetes. Generally, spirochete colony-forming units ranged between 10⁴ and 10⁶ per gram wet weight of the top 1 cm of sediment. Spirochete colony-forming units were in greater abundance in the uppermost 1–2 cm of sediment than in sediment taken from depths of 3–5 cm. Apparently, the top 1 or 2 cm of salt marsh sediment can provide a favorable habitat for certain spirochetal species.