Bacterial chromosomal painting for in situ monitoring of cultured marine bacteria

We previously described a new method, bacterial chromosomal painting (BCP), for the in situ identification of bacterial cells. Here, we describe the a pplication of this technique to study the ecology and physiology of culture d marine pelagic bacteria from the western Sargasso Sea (WSS). A total of 8 6 bacteria were isolated from seawater collected from near the surface, at a depth of 250 m and from nutrient;amended seawater incubations. The 10 bac terial isolates that were best represented in environmental genomic DNA fro m the WSS were selected using reverse genome probing. BCP hybridization cel l counts were used to determine the depth-specific distribution of one of t he alpha proteobacterial isolates, B5-6, in the WSS during two thermal stra tification regimes: stratified and partially mixed. The maximum cell count measured for B5-6 at the summer deep chlorophyll maximum was approximately 4% of the total cell count. This study is the first application of BCP to n atural environments.