Isolation and Identification of Iron-Oxidizing Microbes

Microbial oxidation of iron is an important part of biogeochemical cycles in mine environment. Iron-oxidizing bacteria are important catalysts of iron cycling in wetland environments. However, little is known about their diversity and distribution. Many bacterial species have been found in soil deposits but only a few pure cultures have been isolated. The aim of this protocol is to isolate iron-oxidizing bacteria from different sources. Here, we describe the procedure for isolation, identification, and characterization of iron-oxidizing bacteria. The classical approach for the cultivation of iron-oxidizing bacteria is agar-based gradient tube method where the bacteria find optimal growth conditions in opposing gradients of oxygen (O2) and dissolved Fe (II). Two separate enrichment cultures are used, and in each, the cells grow in a distinct, rust-colored band in the gel at the oxic-anoxic interface. Another method is non-gradient, 9K medium method to determine the distinct growth characteristics of isolates.