IMAGE COURTESY OF ANDIA CHAVES-FONNEGRA
EDITOR'S CHOICE IN MARINE BIOLOGY
F. Zhang et al., “Phosphorus sequestration in the form of polyphosphate by microbial symbionts in marine sponges,” PNAS, 112:4381-86, 2015.
Fan Zhang, a graduate student in Russell Hill’s lab at the University of Maryland Center for Environmental Science, was using microscopy to study how Caribbean coral reef sponges process nitrogen. But the sponges autofluoresced so brightly that their nitrogen-fixing bacterial symbionts were difficult to see. To detect the bacteria, Zhang applied a blue fluorescent stain called DAPI, but to his surprise, he saw something else: bright yellow dots.
An Internet search suggested that polyphosphate—chains of phosphate molecules—could be the cause, and indeed, with specific extraction methods and scanning electron microscopy, Zhang’s team observed polyphosphate granules that accounted...