Discovery could benefit horseshoe crabs, birds

[Donna]

In addition to saving human lives, a new device to detect bacteria in drugs and medical tools could save those of horseshoe crabs and birds.

Detecting bacteria in drugs and medical equipment ensures that no endotoxins will trigger dangerous immune reactions in human patients. The new sensor uses chemical compounds harmlessly obtained from frog skin, forgoing the four-decade-old process of using crab blood extracted through a potentially lethal process.

Mechanical and aerospace engineering professor Michael McAlpine and his team of engineers developed the sensor and published their findings last month in the Proceedings of the National Academy of Sciences.

According to Manu Mannoor GS, who worked on the project, pharmaceutical companies have used horseshoe crab blood to test for bacteria for the past 40 years. A solution containing horseshoe crab blood, called limulus amebocyte lysate, or LAL, congeals when in contact with harmful bacteria. The companies extract 30 percent of a crab’s blood, and nearly one-third of the crabs used die upon return to the ocean.

In their lab, the researchers synthesized antibacterial peptides from the skin of African clawed frogs. These antibacterial peptides, which are tiny amino acid chains, guard the frogs against infection. McAlpine said this new method does not harm the frogs.

McAlpine and his assistants engineered a way to connect the antibacterial peptides to an electronic chip. When this chip is exposed to pathogenic E. coli, salmonella and other harmful bacteria, it sends out electrical alerts. 

“The new electronic chip is very robust,� McAlpine said. “It is a significant improvement for monitoring water quality because instead of sending the water sample away to a lab, the sensor can test it right away.�

People have used the LAL method for sensing contamination since the 1970s, and prior to its implementation, patients often contracted fevers from deficient sterilization.

The heavy use of horseshoe crabs has strained their population and affected other species in the their ecosystem, especially red knot shore birds, which feed on crab eggs.

“Even though horseshoe crabs are in the ocean and these birds are flying around terrestrially, they affect each other,� said Cleo Chou, a graduate student in the ecology and evolutionary biology department.

The population of a flock of red knots from the South American islands of Tierra del Fuego, for example, decreased to 27,000 from 51,000 between 2000 and 2002, according to a study by researchers at the University of Toronto.

Ecology and evolutionary biology professor David Wilcove said the crab eggs are a vital food source for the red knots, who annually migrate thousands of miles from Tierra del Fuego to the Canadian Arctic. During their spring migration, they stop at Delaware Bay to feed.

“The birds put on fat deposits equal to almost half their body weight by feasting on the crab eggs, and they use that energy to complete their northward migration,� Wilcove said.

In an effort to stymie population decreases, New Jersey banned crab harvesting, and Delaware, Maryland and New York capped the number of crabs harvested at 150,000 per year.

The red knot population, as measured at Delaware Bay, has shown signs of recovery, growing 33 percent between 2008 and 2009. The 2009 population of 24,000 does, however, fall far below the 100,000 to 150,000 counted 20 years ago.

“We should be able to get to a realm where we are able to compete with the horseshoe crab blood LAL method,� McAlpine said. “The next important step is to find ways to make the chip’s sensitivity better, and we have ideas for how to do that.�