A call to expand the dimensions of halide-philicity.

Microbiology research has historically associated the term halophily with sodium chloride. Today, other halides are taking on increasing importance with the broader use of other halide anions, their oxyanions, and thousands of organohalides. This has led to a wider and human-altered distribution of halides and organohalides in the environment, as well as increased efforts to bioengineer microbes to synthesize or degrade organohalides and to tolerate their associated halide salts. In this context, it needs to be more widely appreciated that microbial responses to fluorine, chlorine, bromine, or iodine are vastly different. Moreover, the way microbes handle a given halide may differ when they are paired with different counter cations. In addition, the microbial responses may differ when the halogens are in the external environment or liberated inside the cell by cytoplasmic enzymes, for example, by dehalogenases. In this commentary, we seek to highlight these differences and offer a call for future research.