Biomedicine

From the Labs: Biotechnology

New publications, experiments and breakthroughs in biotechnology–and what they mean.

Cellulose Enzymes from the Termite Gut
A metagenomic study of the microbes that live in wood-eating termites could suggest new ways to make cellulosic ethanol

A massive genetic analysis of the microbes in the gut of Nasutitermes termites, shown here, could yield more efficient enzymes for generating cellulosic ethanol.

Source: “Metagenomic and Functional Analysis of Hindgut Microbiota of a Wood-Feeding Higher Termite”
Jared R. Leadbetter et al.
Nature 450: 560-565

Results: In a massive genomic study of the microbes living within the termite gut, scientists may have identified close to a thousand enzymes that break down wood.

Why it matters: Biofuels made from cellulosic biomass, including cornstalks, perennial grasses, and wood chips, could provide a cheaper and more environmentally beneficial alternative to corn-derived ethanol. However, breaking down cellulose into simple sugars that can be fermented into ethanol is a complex, inefficient, and expensive process. The newly identified cellulose-digesting proteins could shed light on termites’ wood-eating capacity and suggest cheaper, more efficient enzymes for generating cellulosic ethanol.

Methods: Scientists collected Nasutitermes termites from Costa Rica and isolated DNA from the microbes living in part of the insects’ gut. They then sequenced and analyzed the genomic material from the many different types of bacteria, searching for particular sequences known
from other studies to be
linked to the ­ability to break down cellulose.

Next steps: Researchers are now testing some of the newly identified microbial enzymes for their wood-digesting ­ability, as well as searching for combinations of different enzymes that work together synergistically.

Deciphering Human Differences
Chunks of shuffled DNA in the human genome could underlie many diseases

Source: “Paired-End Mapping Reveals Extensive Structural Variation in the Human Genome”
Michael Egholm, Michael Snyder, et al.
Science 318: 420-426

Results: Scientists have uncovered extensive regions in the human genome where chunks of DNA have been deleted, copied, or completely re­arranged. More than a thousand structural variations were identified between two individual genomes–many more than other studies have found.

Why it matters: Most studies of genomic variation have focused on individual bases, or DNA “letters.” In the last few years, however, several studies have shown that structural variations in DNA may be at least as important as single-letter variations. Mapping and characterizing these structural variants could be key to understanding human diversity and the origins of many diseases.

Methods: Snyder and his colleagues analyzed the genomes of two individu­als, one of African descent and one of European descent. They chopped the genomes into millions of fragments, each 3,000 bases long, and tagged the fragments’ ends. They then sequenced the ends of each fragment and compared them with a reference genome, derived from the Human Genome Project. If the overall sequence of the fragments was either shorter or longer than the corresponding piece of the reference genome, the researchers concluded that a piece of DNA had probably been copied or deleted.

Next steps: The company whose sequencing technology was used in the study, 454 Life Sciences of Branford, CT, aims to repeat the experiment on 100 individuals. Scientists eventually aim to generate an inventory of the structural variations associated with human disease.

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