Stained diatom showing freshly
precipitated silica; © University
Diatoms, most of which are far too tiny to see without magnification, are incredibly important in the global carbon cycle, says Thomas Mock, a University of Washington postdoctoral researcher in oceanography and lead author of the paper. During photosynthesis, diatoms turn carbon dioxide into organic carbon and, in the process, generate oxygen.
The new work took advantage of the genomic map of the diatom Thalassiosira pseudonana published in 2004 by a team led by UW oceanography professor Virginia Armbrust. Thalassiosira pseudonana is encased in a hatbox-shaped shell comprised of a rigid cell wall, made mainly of silica and delicately marked with pores in patterns distinctive enough for scientists to tell it from other diatoms.
Armed with the genomic map, the researchers changed environmental conditions in laboratory cultures of Thalassiosira pseudonana, for example limiting the amount of silicon and changing the temperatures. Then researchers used what’s called “whole genome expression profiling” to determine which parts of the genome were triggered to compensate.
Scientists since the late 1990s have found only a handful of genes that influence diatom shell formation. The work with Thalassiosira pseudonana identified large, previously unknown subsets. A set of 75 genes, for example, was triggered to compensate when silicon was limited.
The researchers were surprised to find another subset of 84 genes triggered when either silicon or iron were limited, suggesting that these two pathways were somehow linked. Under low-iron conditions, the diatoms grew more slowly and genes involved in the production of the silica shell were triggered. Individual diatoms also tended to clump together under those conditions, making them even heavier and more likely to sink.
Diatoms can manipulate silica in ways that engineers can only dream about. University of Wisconsin professor Michael Sussman says the new findings will help his group start manipulating the genes responsible for silica production and potentially harness them to produce lines on computer chips. This could vastly increase chip speed because diatoms are capable of producing lines much smaller than current technology allows, he says.
COMPAMED.de; Source: University of Washington