Bacterial Cooperation

Two different kinds of marine bacteria cooperate to produce a compound that apparently protects the organisms from other microbes, according to Texas A&M University researchers.

The findings represent an unusual example of synergistic interaction among bacteria for the production of a natural product, says Helge B. Bode, who studies bacterial natural products at Saarland University in Saarbr??cken, Germany.

The bacterial partnership wouldn't have been discovered if the Texas A&M researchers had relied on classical techniques for studying natural products synthesis. Traditionally, individual marine species are examined in isolation, explains Texas A&M bioorganic chemist Coran M. H. Watanabe. But she suspected that interactions among different species in the marine environment might lead to the production of additional natural products.

Watanabe and her colleagues collected a mixture of bacteria from the floor of the ocean off Oahu, Hawaii, the island where she was born. When they cultured the bacterial mix, they discovered that two different species work together to produce a blue metabolite that is harmful to other microbes. Pure cultures of the individual bacteria did not produce the compound (Chem. Biol. 2006, 12, 1349).

Watanabe's team identified the metabolite as pyocyanin. The paper includes NMR data on the molecule's structure, which Watanabe says correct data published earlier by another group. The bacteria were identified previously as strains of Pseudomonas aeruginosa and Enterobacter.

The cooperative synthesis of pyocyanin, Watanabe believes, relies on a unique type of quorum sensing—or chemical communication that leads to gene expression—between the two species of bacteria. She thinks that a chemical dialogue between the two types of bacteria leads one type to produce a compound that activates genes in the second bacterium, inducing it to produce pyocyanin. Watanabe is working to identify that gene-activating compound.

Watanabe says she hopes her team's mixed-culture approach will become a general strategy for "accessing novel natural products from otherwise silent biosynthetic pathways."